Keel or "Through Hull" cooling?

[Rappey]

I posted that comment over 2 years ago. Have you taken that long to think up your reply?

Haha. Shall i wait another two years before i reply.?

I didn't look at the date.
Like others i log on, click "new posts" and rarely think about the date posted.
Different threads about the same thing leads to repeated information.
I find one thread easier than having to trawl through many.

 

[Saltsail]

Good time of the day to you all!
I would like to leave my opinion here also!

Internal cooling requires to have radiator+fan, any car mainly used in large cities do get hot, this is when cooling fan comes into action, boat cannot get same kind of air flow thru it radiator because it doesn't exist! (where would you fit your radiator?) Reason all this stupid engineers designed raw cooling system is for us brave guys to keep going.
Where would you fit your radiator? Keel? if there is any issues what would be easier to examine you cooling system outside or just change your impeller inside?
There is plenty of options for dry exhaust option but they only suitable for local trips!

 

[doris1914]

Good time of the day to you all!
I would like to leave my opinion here also!

Internal cooling requires to have radiator+fan, any car mainly used in large cities do get hot, this is when cooling fan comes into action, boat cannot get same kind of air flow thru it radiator because it doesn't exist! (where would you fit your radiator?) Reason all this stupid engineers designed raw cooling system is for us brave guys to keep going.
Where would you fit your radiator? Keel? if there is any issues what would be easier to examine you cooling system outside or just change your impeller inside?
There is plenty of options for dry exhaust option but they only suitable for local trips

Hello saltsail, no one is saying it's the perfect systembut it certainly can be a very good system and has been for many
Almost all commercial boats will have keel cooling

If you had read my previous post you would have noticed that our boat has a full size engine room, it measures 16'x11' x6'6" so we have plenty of room to install a radiator and fan if we chose to, but that's just not a practical system not least due to the volume of airflow that would be required through the engine room.

We also have a 'proper' funnel which we will use to exhaust the engines.
Why would a dry exhaust only be good for short trips? There are plenty of boats that run dry exhausts that cruise quite extensively.
I am quite open to reasoned opinions backed up with anecdotal proof as to why keel cooling would be such a bad choice but Im afraid that simply putting forward an opinion based on opinion or prejudice without facts or evidence to back it up holds very little weight in a discussion.
So far the bonafide marine engineers I have spoken too are of the opinion that keel cooling is a bonafide way of cooling our engines.

 

[MapisM]

I am quite open to reasoned opinions backed up with anecdotal proof as to why keel cooling would be such a bad choice but Im afraid that simply putting forward an opinion based on opinion or prejudice without facts or evidence to back it up holds very little weight in a discussion.
So far the bonafide marine engineers I have spoken too are of the opinion that keel cooling is a bonafide way of cooling our engines.

You will struggle to find reasoned opinions against keel cooling, for the type of vessel you are dealing with.
In fact, the main reason why raw water cooling is by far the most popular setup in pleasure boats is that most pleasure boats are fast.
And this implies very powerful engines proportionally to the boat size, for which keel cooling simply couldn't keep up with the heat dissipation required.
I mean, it could, but the amount of tubes that should be put under the hull (which normally doesn't even have a keel) would become a sort of permanent handbrake, which is exactly what you don't want, on planing boats.
Besides, also the dry stack that should run through the boat interiors should be massive, and would make the saloon a sort of sauna during the summer.
For displacement boats instead, keel cooling and dry stack make a lot of sense.
Who wouldn't want to keep salt water outside the boat where it belongs?
It's no coincidence that long range passagemakers (like Nordhavns, but not only) are the only type of pleasure boats adopting this setup.
What Saltsail meant by "only suitable for local trips" must be that you can only use it for cruising planet Earth, but not to reach the moon, I suppose...?!?

 

[TLouth7]

Haha. Shall i wait another two years before i reply.?

I didn't look at the date.

This is precisely the problem with resurrecting old threads. People don't notice, and so instead of replying to the new poster (who would be OP if they just asked their question in a new thread) they reply to OP who had their question answered many years ago and probably doesn't need any extra input.

A neat solution is for the new poster to create a new thread, but link to the original for interest (though there is a risk this results in people accidentally replying to the linked thread).

The Boat Design Net forums get round this neatly by having a message appear when you try to reply to an old thread warning against resurrecting.

 

[Dockhead]

Some helpful replies, some less so (!).
I appreciate the point about keel coolers possibly being more vulnerable to damage, but in the event of a total failure the engine would then be directly sea water cooled until repairs were made, and if you've hit anything hard enough to damage it you might have more urgent problems anyway...
Regarding the issue of internal corrosion, this wouldn't be an issue if the keel cooler/skin tank wasn't steel.

Prv, sorry wasn't meaning to disparage direct cooling... it's a perfectly good idea if your engine isn't steel or cast iron and can tolerate chronic scaling of coolant passages.

Keel cooling has a number of advantages, and I've looked into it for the design of a purpose-designed yacht for high latitudes which should be capable of dealing with some ice. Ice can clog a conventional cooling system so you see a certain number of high latitude boats with keel cooling and dry exhaust.

The big issue as others have mentioned is the exhaust. Dry exhaust is just about not practical for a smallish GRP yacht. Might be more practical with special built components -- really good insulated fittings to get the exhaust through the hull, really good flexible highly insulated pipe. If keel cooling were more common and such components were better developed and mass produced, then it might work better.

But besides the main cooling system and the exhaust, yacht machinery needs cooling of lube oil, gearbox oil, and in my case, turbocharger aftercooler. All this is greatly simplified by conventional sea water cooling systems.

So a wet exhaust has such huge advantages for small GRP yachts that it's pretty hard to imagine any designer doing without it without some special reason like sea ice.

Now you can have wet exhaust AND keel cooling. I've seen that on at least one ice-capable purpose built yacht. The duplication of systems is inelegant however, expensive, heavy, complex, for little purpose.

Yet another approach is AIR COOLING of the yacht engine. I've seen one high latitude yacht with such an arrangement. This is very elegant indeed but still leaves the exhaust, gearbox oil, lube oil as problems -- the exhaust is not as big a deal if the yacht is metal.

This subject is not exactly a burning yacht design issue because the conventional systems with rubber impeller pumps is actually highly satisfactory, as several here have mentioned. I have two such systems on my boat -- one for genset, one for main. The sea water pump for the Yanmar main is well below the water line so can't run dry -- what kills my genset pump on a regular basis. The Yanmar pump is bulletproof -- I get 1000 hours between impellers, which are still quite good after 1000 hours. I have (well not me but Cowes Yacht Haven guys doing a lift without me) run it for 15 minutes at a time with the sea cock closed, then another year and 400 hours without a problem. I've never had an underway impeller failure on a yacht engine is many decades of cruising, but just in case I always have a quick change kit next to the engine -- 5 minutes is enough. Not a big deal.

Cooling using sea water is a good, reliable system, not something I would feel any need to change for something else, but for the sea ice issue.

 

[Saltsail]

Just to add, if any of your cooling pipes fail along your keel, only way to inspect them is haul-out. For pleasure use id suggest raw cooling only! But there are few buts, depending on how you planning to use ur boat.
(thank you for kind reply! i did missed some of your posts)

 

[nortada]

Keel cooling has a number of advantages, and I've looked into it for the design of a purpose-designed yacht for high latitudes which should be capable of dealing with some ice. Ice can clog a conventional cooling system so you see a certain number of high latitude boats with keel cooling and dry exhaust.

The big issue as others have mentioned is the exhaust. Dry exhaust is just about not practical for a smallish GRP yacht. Might be more practical with special built components -- really good insulated fittings to get the exhaust through the hull, really good flexible highly insulated pipe. If keel cooling were more common and such components were better developed and mass produced, then it might work better.

But besides the main cooling system and the exhaust, yacht machinery needs cooling of lube oil, gearbox oil, and in my case, turbocharger aftercooler. All this is greatly simplified by conventional sea water cooling systems.

So a wet exhaust has such huge advantages for small GRP yachts that it's pretty hard to imagine any designer doing without it without some special reason like sea ice.

Now you can have wet exhaust AND keel cooling. I've seen that on at least one ice-capable purpose built yacht. The duplication of systems is inelegant however, expensive, heavy, complex, for little purpose.

Yet another approach is AIR COOLING of the yacht engine. I've seen one high latitude yacht with such an arrangement. This is very elegant indeed but still leaves the exhaust, gearbox oil, lube oil as problems -- the exhaust is not as big a deal if the yacht is metal.

This subject is not exactly a burning yacht design issue because the conventional systems with rubber impeller pumps is actually highly satisfactory, as several here have mentioned. I have two such systems on my boat -- one for genset, one for main. The sea water pump for the Yanmar main is well below the water line so can't run dry -- what kills my genset pump on a regular basis. The Yanmar pump is bulletproof -- I get 1000 hours between impellers, which are still quite good after 1000 hours. I have (well not me but Cowes Yacht Haven guys doing a lift without me) run it for 15 minutes at a time with the sea cock closed, then another year and 400 hours without a problem. I've never had an underway impeller failure on a yacht engine is many decades of cruising, but just in case I always have a quick change kit next to the engine -- 5 minutes is enough. Not a big deal.

Cooling using sea water is a good, reliable system, not something I would feel any need to change for something else, but for the sea ice issue.

Coming late to this discussion, I have been involved with a number of boats with through hull cooling and they have been nothing but trouble, certainly not reliable.

In some cases more holes in the hull and the increased risk of taking on water. From my, albeit limited experience, I would not touch a boat with through hull cooling.

 

[oldmanofthehills]

I have recently bought what was originally a keeled cooled ex lifeboat engine. It was now for a GRP Hulled boat.

So how could one fit it? On a narrow boat the cooling plate would fit against the steel hull. But in a GRP hulled boat it would need a square slot through hull just where the long keel goes (and all such holes are a source of leakage - think of saildrives). Of course I could rig a heat exchanger pipe through the hull and have the whole lot causing drag and giving problems.

Happily the supplier converts such engines to raw water cooling or in my case to rawwater/heatexchanger/freshraw. And such water cooling means I can use rubber exhaust pipes and plastic fittings rather than metail fittings customised to wind round the narrow voids of a small boat, and still presenting a fire risk.

Keel cooling great for build-in solutions or steel hull, but fairly unhelpful otherwise.

 

[Saltsail]

NORTADA Thank You for confirming this! 100% agree with you!

 

[TNLI]

Does anyone know why small leisure boat engines are normally fitted with engine driven sea water cooling?
I'm actually a marine engineer, so well experienced with big sea water cooled heat exchangers, but I'm actually pretty baffled by the marine leisure engine industry's dependance on somewhat unreliable Jabsco pumps for providing the essential supply of sea water cooling to tiny, easily blocked tube type heat exchangers.
I know that one of the reasons is that the sea water cools and silences the engine exhaust after passing through the heat exchanger, but this seems to be inviting even more problems by bringing the sea water into proximity with the combustion system and the engines innards.
To my mind a more sensible, efficient, and reliable arrangement would be to have keel or "through hull" cooling and a dry exhaust system, this is what's fitted to our lifeboats which are fitted with 60hp diesels and required statutorily to be capable of running continuously for 24 hours.
The excess heat from the exhaust could be dissipated by better engine ventilation, or even have a water cooled manifold, and exhaust noise addressed by fitting silencers as on cars.
One of the well known engine manufacturers quotes a need for 7 square feet of cooling area for a 25hp engine, this sounds quite a lot until you think that a 2inch diameter pipe 11 feet long has about 7 square feet of surface area, so fitting even the simplest arrangement of keel cooling shouldn't have too much of an adverse effect on a hulls hydrodynamics, and even if this was a problem it would be relatively easy to build flush fitting skin coolers of adequate surface area.
Other advantages would be not having a sea strainer to keep clean and one less through hull cock, having a supply of hot water for boat services such as interior heating and hot water, and of course the ability to run the engine for short periods while the hull was not in the water.
The problems of fouling of the external heat exchanger could be alleviated by using a copper skin, and of course it's high skin temperature (at the inlet end) might give the barnacles reason to go elsewhere. I would always advise oversizing the cooler to provide a factor of safety against any fouling that did occur.
My best guess is that some accountant somewhere decided that it would be cheaper to fit a cheap and nasty sea water pump to push water through a relatively expensive tube type cooler, than it would be to drill two holes in the hull and bolt a copper tube onto them, and to hell with the inconvenience and need for constant vigilance and maintenance needed with a sea water cooled system...

I'm building an offshore lifeboat with an old fully reconditioned BMC 1.5D that will have keel cooling, and I agree with everything Paul said about how bad an idea a suck and spit system is. You could write a book about why such systems are unreliable in comparison with a well designed and correctly installed keel cooler. The only good point about suck and spit cooling is that it's cheap and easy to install.

Although I'm a fan of keel cooling for serious work or rescue boats, I definitely would think twice before installing such a system for a wood, glass or plastic boat, as the external cooler will prove expensive and interesting to install. It is sometimes possible to install cooling pipes, (Good for an HF ground plain), when a yacht is built that has internal lead ballast in its keel. It's far easier to install if the hull is made of aluminium or steel, cos you can do the job without hauling out by fitting a cooling plate inside the hull. Many steel canal boats in the UK have that type of keel cooling.
Engines designed or adapted for keel cooling are different in plumbing terms, particularly if the engine has a hydraulic box like my PRM 100, as that has to be part of the cooling system. Hope to install my donkey later this month, once I finish off the plumbing and wiring. The crankshaft will also need to be sent across town to be checked and polished by real experts. As you can see in the picture I can't remove it myself too easily.

 

[TLouth7]

So, I'll watch out for further contributions in 2022...

Comment made by OP in 2017, five years after starting the thread.

Haha. Shall i wait another two years before i reply.?

Comment made by a previous thread resurrector in 2020.

So I guess you are bang on time!

 

[vyv_cox]

I'm building an offshore lifeboat with an old fully reconditioned BMC 1.5D that will have keel cooling, and I agree with everything Paul said about how bad an idea a suck and spit system is. You could write a book about why such systems are unreliable in comparison with a well designed and correctly installed keel cooler. The only good point about suck and spit cooling is that it's cheap and easy to install.

Although I'm a fan of keel cooling for serious work or rescue boats, I definitely would think twice before installing such a system for a wood, glass or plastic boat, as the external cooler will prove expensive and interesting to install. It is sometimes possible to install cooling pipes, (Good for an HF ground plain), when a yacht is built that has internal lead ballast in its keel. It's far easier to install if the hull is made of aluminium or steel, cos you can do the job without hauling out by fitting a cooling plate inside the hull. Many steel canal boats in the UK have that type of keel cooling.
Engines designed or adapted for keel cooling are different in plumbing terms, particularly if the engine has a hydraulic box like my PRM 100, as that has to be part of the cooling system. Hope to install my donkey later this month, once I finish off the plumbing and wiring. The crankshaft will also need to be sent across town to be checked and polished by real experts. As you can see in the picture I can't remove it myself too easily.

Don't underestimate the benefits of a wet exhaust system. A dedicated seawater pump for the exhaust would be needed. A hot exhaust on a yacht would be difficult to arrange safely and quietly. I have quite a bit of experience with hot exhausts on small motorboats and find them nothing but trouble.

 

[TNLI]

Don't underestimate the benefits of a wet exhaust system. A dedicated seawater pump for the exhaust would be needed. A hot exhaust on a yacht would be difficult to arrange safely and quietly. I have quite a bit of experience with hot exhausts on small motorboats and find them nothing but trouble.

So what benefits do you get from your suck and spit cooling system ?? I'm very familiar with both types and all offshore lifeboats have keel cooling for very good reasons, mostly relating to reliability and lack of extra maintenance items. I like diesels that can be run when stuck in ice or beached on some nice sand bar or mud bank. I also don't want to have to adjust a second belt, or clean out the water filter and worst of all suffer an overheat incident when the impeller fails, or the heat exchanger gets badly blocked up. Keel cooling is the simplest way of cooling a diesel, and it can even be used to heat the interior if the design allows for under cabin sole heating with inside cooler plates. No need for an inlet seacock, as it's a closed loop system.

You do not need an extra pump or intake for a wet exhaust, just all stainless pipes including a loop before the final stainless silencer box. Not too expensive as all the parts I'm using are from car or truck tuning manufacturers. I'm also installing a small vent line to drain the final loop that vents a small amount of gas overboard, and an external hinged exhaust pipe fitting on an existing stainless pipe. No need for any rubber pipes that melt when the spit and suck system gets blocked or the pump fails. I can assure you that the only reason manufacturers install suck and spit cooling is that it's cheaper. The extra cost of the exhaust system is around 2 to 300 quid depending on whether you need a new outlet pipe on the engine and how big a silencer is required. The extra cost of the cooling tank, radiator or pipes depends on the size of the engine and just what you intend to fit. The header tank will also need to be re-plumbed in some cases.

If you have or are buying a recon BMC, the keel cooled versions do not need expensive Bowman rubber end caps that have a nasty habit of splitting when old. The heat exchanger, (More of a header and distribution tank in reality), does not need rubber anything, which is another plus.

 

[oldmanofthehills]

Don't underestimate the benefits of a wet exhaust system. A dedicated seawater pump for the exhaust would be needed. A hot exhaust on a yacht would be difficult to arrange safely and quietly. I have quite a bit of experience with hot exhausts on small motorboats and find them nothing but trouble.

Quite right. It has taken 7 hours for the yard to remove and replace the manual bilge pump pipe which essentially follows the same necessarily convoluted route as the exhaust from engine compartment to distance stern, and that is with stiff but flexible pipe. Doing it with metal pipe would be a nightmare in itself and if not water cooled would run surface hot pipe past all kinds of inflammable stores including our fuel tanks.

No doubt it would be easier in fishing boats with large engine bays and no need for engine to be able to operate when heeled right over.

 

[TNLI]

Why is there a need for the outlet pipe for the exhaust need to be routed more than around 10ft on an average size boat ?? There is no need to have an exhaust outlet at the stern, in fact if you can even use bubbler pipes as fitted to drug cartel surface runners to hide their exhaust IR signature. Stainless tubing is not expensive if you buy it from a sensible car or truck exhaust shop or garage. The outlet for a manual bilge pump should be as close as possible to the pump and not too far above the waterline with a loop or non return valve if required.

It is easier to install keel cooling when building or doing a hull up project like mine, as it needs to be included in the interior design to some extent. If your diesel has direct salt water suck and spit with no heat exchanger, which is bad news in long term engine wear due to hot spots forming from Calc deposits in low flow areas, like many small single and twin cylinder marine diesels like some Yanmar 1 and 2 GM's, it is easier to install keel cooling than if you need to convert the entire cooling system to enjoy all the benefits from keel cooling, (No idea why it's called that as no many boats have pipes inside or near the keel, if you have one),

 

[vyv_cox]

So what benefits do you get from your suck and spit cooling system ?? I'm very familiar with both types and all offshore lifeboats have keel cooling for very good reasons, mostly relating to reliability and lack of extra maintenance items. I like diesels that can be run when stuck in ice or beached on some nice sand bar or mud bank. I also don't want to have to adjust a second belt, or clean out the water filter and worst of all suffer an overheat incident when the impeller fails, or the heat exchanger gets badly blocked up. Keel cooling is the simplest way of cooling a diesel, and it can even be used to heat the interior if the design allows for under cabin sole heating with inside cooler plates. No need for an inlet seacock, as it's a closed loop system.

You do not need an extra pump or intake for a wet exhaust, just all stainless pipes including a loop before the final stainless silencer box. Not too expensive as all the parts I'm using are from car or truck tuning manufacturers. I'm also installing a small vent line to drain the final loop that vents a small amount of gas overboard, and an external hinged exhaust pipe fitting on an existing stainless pipe. No need for any rubber pipes that melt when the spit and suck system gets blocked or the pump fails. I can assure you that the only reason manufacturers install suck and spit cooling is that it's cheaper. The extra cost of the exhaust system is around 2 to 300 quid depending on whether you need a new outlet pipe on the engine and how big a silencer is required. The extra cost of the cooling tank, radiator or pipes depends on the size of the engine and just what you intend to fit. The header tank will also need to be re-plumbed in some cases.

If you have or are buying a recon BMC, the keel cooled versions do not need expensive Bowman rubber end caps that have a nasty habit of splitting when old. The heat exchanger, (More of a header and distribution tank in reality), does not need rubber anything, which is another plus.

I made no reference to the engine cooling system.

A hot exhaust in a yacht would be disastrous in my opinion , difficult to route safely and dangerous when things go wrong, which inevitably they will. I have spent hours welding failed exhausts, adding flexible sections and trying to find gas leaks. A wet exhaust in rubber hose is the only way to go.

 

[TNLI]

A hot exhaust in a yacht would be disastrous in my opinion , difficult to route safely and dangerous when things go wrong, which inevitably they will. I have spent hours welding failed exhausts, adding flexible sections and trying to find gas leaks. A wet exhaust in rubber hose is the only way to go.

Nearly every canal boat that is used during the winter or yacht with a diesel heater has to have a hot exhaust, and the least problematic is the one for a keel cooled- engine. If you are concerned about going into an engine bay with hot pipes, just fit a stainless wrap around pipe to stop anyone who likes grabbing hold of an exhaust pipe from getting burnt, or real cladding, which is not expensive if you avoid buying one that has marine stamped on it.

If you do not know how to gas weld correctly, or lack the right variable output arc welder or safety gear, find a good professional, although if you fit overlapping exhaust pipes to the down pipe from the engine onto the silencer, the welds will not fatigue crack. It also helps to use a good quality exhaust sealant when fitting the various overlap joints. So the exhaust system should not leak even before it is Mig or Tig welded. Argon & C02 mix for MIG is good enough for a reasonable finish, but if you are real fussy, nothing beats TIG welding with Helium. Make sure the welder is using the correct type of welding sticks for the type of stainless being used, and if you weld galvanised anything grind the Zinc off first! Galvanised exhaust tubes are a lot cheaper than stainless, but you must use a flexible section somewhere, and that will need to be stainless.

Gas leaks are possible from any type of badly designed or installed system, Chinese jubilee clips or split rubber hoses in particular, so fit a proper CO and smoke detector near the engine bay vent

Silencer for BMC 1.5D:
STAINLESS STEEL SINGLE TIP PERFORMANCE EXHAUST MUFFLER BACK BOX MFR003 5060483221410 | eBay

Flexible tubing:
Exhaust Pipe Stainless Steel Polylock Flexible Tube With Collars Any Size | eBay

Various joiners and bends:
Exhaust 45 90 180 Degree 38MM - 76MM Mandrel Bend 1.5D T304 Stainless Steel | eBay

External flapper valve:
CUSTOM 38MM -152MM STAINLESS STEEL EXHAUST GENERATORS RAIN CAP FLAP WEATHE COVER | eBay
Note: Spring slam shut version available, or DIY possible with a separate coil spring.

More serious inline muffler:
marine engine exhaust baffle silencer 45mm | eBay

 

[jwfrary]

It is possible to engineer a long lasting and reliable dry exhaust for any yacht of any size I would argue.

However, cost is one prohibitive factor, you would need to use 316L in the manufacture, dip in nitric acid and penetration test welds. High quality Flexible sections would need to be used, these would need to be fitted with V clamps and spares carried as they are a wearable item, much like rubber hose.

Its is in the end far simpler and cheaper to use rubber hose and cheaper plastic silencers.

Added to that reduced noise and heat are welcome additions to the user that values these things against longevity.

While the pumps can be unreliable, they are also easy to replace or repair and so it's a trade off between the two.

The original post mentions lifeboats, which I regard as a special case. They are required to standby unused for long periods of time, with some inspection but in all likelihood a cursory one and there for a rubber type impeller pump would be impractical.

 

[TNLI]

It is possible to engineer a long lasting and reliable dry exhaust for any yacht of any size I would argue.

However, cost is one prohibitive factor, you would need to use 316L in the manufacture, dip in nitric acid and penetration test welds. High quality Flexible sections would need to be used, these would need to be fitted with V clamps and spares carried as they are a wearable item, much like rubber hose.

Its is in the end far simpler and cheaper to use rubber hose and cheaper plastic silencers.

Added to that reduced noise and heat are welcome additions to the user that values these things against longevity.

While the pumps can be unreliable, they are also easy to replace or repair and so it's a trade off between the two.

The original post mentions lifeboats, which I regard as a special case. They are required to standby unused for long periods of time, with some inspection but in all likelihood a cursory one and there for a rubber type impeller pump would be impractical.

I only use 302 or 304 stainless for exhaust systems, 316 is only needed if you want a real shiny finish outside the engine bay. If you fit a silencer or muffler an all metal exhaust makes less noise than the engine and downpipe.

I forget how many mayday or pan calls from boats with engines that have overheated due to some type of cooling system failure, often just a kaput impellor, Not many boaters seem to be capable of repairing a pump at sea, or do not have a spare, (It's quicker to replace the pump in most cases).

Lifeboat Regs are not a special case as many engine and electrical parts are adhered to by modern offshore self righting fishing and oil industry support boats, like 2 start batteries and very good bilge pumps. My own boat will have 6 bilge pumps, as I need 2 in each water tight compartment, plus a mobile 240V one. I also adhere to USCG Regs that insist on unsinkability with one main bulkhead failed. So I plan to stuff the 2 side lockers above the 2 fuel tanks with old life jackets and bags of pasta.