Keel or "Through Hull" cooling?

[vyv_cox]

Canal boats and yachts differ considerably. The short exhaust pipe on a canal boat does not normally pass through accommodation or lockers, whereas on most yachts it does. The length of pipe is an issue if the engine is on sufficiently flexible mountings, fatigue fracture being a real possibility.
My gas welding is ok, I TIG weld using argon. My hot exhaust experience is with small motorboats. It is not a system I would recommend. And over many years I have had very few problems with wet exhausts, or with directly or indirectly cooled engines.

 

[Tranona]

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),

I don't see why you keep on about this when your requirements and boat are so different from that of the typical cruising yacht. It is not easy to engineer either keel cooling with external pipes not a dry exhaust into a GRP boat. A heat exchanger cooled is as close to ideal as you can get for the purpose which is why it is almost universally fitted. Zero benefit of keel cooling. Again canal boats are different and there is a good argument for keel cooling in this application.

 

[TNLI]

Canal boats and yachts differ considerably. The short exhaust pipe on a canal boat does not normally pass through accommodation or lockers, whereas on most yachts it does. The length of pipe is an issue if the engine is on sufficiently flexible mountings, fatigue fracture being a real possibility.
My gas welding is ok, I TIG weld using argon. My hot exhaust experience is with small motorboats. It is not a system I would recommend. And over many years I have had very few problems with wet exhausts, or with directly or indirectly cooled engines.

No they do not differ much, as there are lots of different types of yachts, engines, heating and cooling systems. Same goes for canal boats, although more of them are made of steel. I've owned 2 very different yachts and both had short exhaust pipes at the stern, just like most canal boats. A gen set in the middle or bow is more problematic in exhaust terms, although you will find many gen sets outside the main engine bay.

If you click on my links it shows how to join the stainless tubes to the engine, as there are several different options, just a s there are in canal boats. Never heard of a fatigue crack in a keel cooled exhaust system that was correctly installed. Much more likely an old jubilee clip or rubber hose will leak. If you have a very small boat, I would not recommend a keel cooler unless it's built in during the build, as there might not be enough room around the engine to make removing and installing a new all steel exhaust system and cooler plate. For my 35hp diesel that plate is only 1m square. It would be less trouble to just install a directly salt cooled engine like a Yanmar 1 or 2GM, unless you need to use your boat on trips where it might get stuck in ice, or in shallow weed infested areas where the engine cooling intake filter blocks very quickly.
If you like reliable engines, then try to give up accepting the low standards set by most manufacturers and think about keel cooling, dual start batteries, and dual primary fuel filters, even if your boat only has one tank. That way you will not get stuck waiting for a tow or finish up shouting mayday just because the primary fuel filter has blocked up. Also fit at least 2 good bilge pumps even with a small boat, and make sure your pumps can handle the inflow rate from a split hose or failed thru hull, (They can be knocked out during a serious grounding unless made of stainless or bronze, but alas many are not. Delrin is also good but more expensive than stainless thru hulls or sea cocks.

 

[TNLI]

I don't see why you keep on about this when your requirements and boat are so different from that of the typical cruising yacht. It is not easy to engineer either keel cooling with external pipes not a dry exhaust into a GRP boat. A heat exchanger cooled is as close to ideal as you can get for the purpose which is why it is almost universally fitted. Zero benefit of keel cooling. Again canal boats are different and there is a good argument for keel cooling in this application.

A good boat builder or marine engineer will find fitting keel cooling easy, but let them decide whether to use a plate or tube system. The only ideal thing about suck and spit heat exchanges is the low cost, assuming you are not a DIY owner who knows where to find cheap cooling pipes or thin tanks.
If you get the installation right in design and silencer terms, the final result is less noise, not more if you lag the main pipes in particular. No need to suffer the terrible spitting, splashing or gurgling sounds. Just the rumble of your beloved main donkey.

Good you tub clip:
Wet Exhaust vs Dry Exhaust - YouTube

 

[vyv_cox]

No they do not differ much, as there are lots of different types of yachts, engines, heating and cooling systems. Same goes for canal boats, although more of them are made of steel. I've owned 2 very different yachts and both had short exhaust pipes at the stern, just like most canal boats. A gen set in the middle or bow is more problematic in exhaust terms, although you will find many gen sets outside the main engine bay.

If you click on my links it shows how to join the stainless tubes to the engine, as there are several different options, just a s there are in canal boats. Never heard of a fatigue crack in a keel cooled exhaust system that was correctly installed. Much more likely an old jubilee clip or rubber hose will leak. If you have a very small boat, I would not recommend a keel cooler unless it's built in during the build, as there might not be enough room around the engine to make removing and installing a new all steel exhaust system and cooler plate. For my 35hp diesel that plate is only 1m square. It would be less trouble to just install a directly salt cooled engine like a Yanmar 1 or 2GM, unless you need to use your boat on trips where it might get stuck in ice, or in shallow weed infested areas where the engine cooling intake filter blocks very quickly.
If you like reliable engines, then try to give up accepting the low standards set by most manufacturers and think about keel cooling, dual start batteries, and dual primary fuel filters, even if your boat only has one tank. That way you will not get stuck waiting for a tow or finish up shouting mayday just because the primary fuel filter has blocked up. Also fit at least 2 good bilge pumps even with a small boat, and make sure your pumps can handle the inflow rate from a split hose or failed thru hull, (They can be knocked out during a serious grounding unless made of stainless or bronze, but alas many are not. Delrin is also good but more expensive than stainless thru hulls or sea cocks.

I disagree with most of what you say about keel cooling and hot exhausts, so no more from me about them.

 

[TNLI]

I think this clip is very good as it covers both types and shows the heat proof cladding and outer tubes on a few different boats:
Wet Exhaust vs Dry Exhaust - YouTube

The last boat has a central engine bay that is more common on trawlers, and it has both systems fitted at present. The type of cladding used is very easy to apply, although I can't find it in ebay for some reason.

 

[Tranona]

A good boat builder or marine engineer will find fitting keel cooling easy, but let them decide whether to use a plate or tube system. The only ideal thing about suck and spit heat exchanges is the low cost, assuming you are not a DIY owner who knows where to find cheap cooling pipes or thin tanks.
If you get the installation right in design and silencer terms, the final result is less noise, not more if you lag the main pipes in particular. No need to suffer the terrible spitting, splashing or gurgling sounds. Just the rumble of your beloved main donkey.

Good you tub clip:
Wet Exhaust vs Dry Exhaust - YouTube

Sorry but you are really so out of touch with the world that most of us here inhabit that it is pointless continuing this discussion.

Of course keel cooling has its merits and of course boats can be built very well using it. HOWEVER that is not the case for cruising yachts particularly if made of GRP as now most are. It has no advantages over the universal use of water cooled engines using pumped seawater and water cooled exhaust. Indeed there are major disadvantages which is why it is not used.

Trawlers, canal boats lifeboats, metal expedition boats for arctic conditions and so on have so little in common with GRP cruising boats so I am not sure why you bother to post - nothing of interest to most people and clearly you don't seem to want to listen and learn about what is appropriate for installing cooling systems in cruising yachts.

 

[Rappey]

I have a morris 1500 diesel out of a J2 which is now 57 yrs old fitted with a bowman heat exchanger. My seawater pump has the same impellor it was launched with 39 years ago. In my 29 years of ownership I've had to rebuild the internals of the high rise mixer for thecost of £70 and replace one very cheap bowman end cap (£7.50) because I keep standing on it when the engine cover is removed. First time I've looked inside the heat exchanger and it's in superb condition.
I also changed the flexipipe between the engine and mixer which is 50mm corrugated stainless at £90.
I would say my total cost of £167.50 over 29 years shows cheapness and reliability .

 

[TNLI]

I have a morris 1500 diesel out of a J2 which is now 57 yrs old fitted with a bowman heat exchanger. My seawater pump has the same impellor it was launched with 39 years ago. In my 29 years of ownership I've had to rebuild the internals of the high rise mixer for thecost of £70 and replace one very cheap bowman end cap (£7.50) because I keep standing on it when the engine cover is removed. First time I've looked inside the heat exchanger and it's in superb condition.
I also changed the flexipipe between the engine and mixer which is 50mm corrugated stainless at £90.
I would say my total cost of £167.50 over 29 years shows cheapness and reliability .

Good to hear from another BMC 1500D fan, as they are something of an exception in reliability terms. How many hours has your engine done since new, and what do you mean by a high rise mixer ? Many BMC have non standard marine conversions done by at least half a dozen different companies, for example my donkey has 6 engine mounts no 4. The extra 2 are to reduce torque induced forces from PRM 100 gearbox and they made a steel plate mounted on the gearbox bell housing to support the extra pair. That kind of extra will complicate the final shaft alignment to some extent. The heat exchangers should stay clean and last longer than 50 years if the coolant is changed, flushed out on occasions and the correct anti freeze mix used with rain water or distilled water if you like spending money,
Although stainless lasts longer than normal steel when used for an exhaust system, nothing lasts forever, and as most BMC 1500's are 50 to 60 years old and very high timers, the exhaust is probably going to need replacing in the not too distant future, although the Vetus waterlocks or muffler boxes seem to survive unless hit by something heavy.

 

[TNLI]

Sorry but you are really so out of touch with the world that most of us here inhabit that it is pointless continuing this discussion.

Of course keel cooling has its merits and of course boats can be built very well using it. HOWEVER that is not the case for cruising yachts particularly if made of GRP as now most are. It has no advantages over the universal use of water cooled engines using pumped seawater and water cooled exhaust. Indeed there are major disadvantages which is why it is not used.

Trawlers, canal boats lifeboats, metal expedition boats for arctic conditions and so on have so little in common with GRP cruising boats so I am not sure why you bother to post - nothing of interest to most people and clearly you don't seem to want to listen and learn about what is appropriate for installing cooling systems in cruising yachts.

I can't understand why plastic boat owners think changing anything is so difficult, as the only drawback to a plastic hull or wooden hull when installing a pair of cooling pipes or plate is the need for them to be attached to the outside of the hull. Installing the pipes in the lead ballast would be better, but a much longer job according to the internal access available to the lead ballast. A bilge keel design is probably the best in terms of installing cooling plates or pipes, as there is no issue over where they can be installed in terms of them not being damaged during a serious grounding.

 

[jamie N]

A year or two ago, I was considering this on my Folkboat, but with a 10hp engine, getting rid of (let's say) 2kW of heat in the exhaust system, within the engine area, below my cockpit sole would've been difficult to endorse as an advantage, given that my boat's wooden.
That's a lot of heat, when the alternative (and usual) methods are simpler, cheaper and more reliable I'd say, by virtue of having such a range of easily available spares on hand.
Both methods work, but the advantages are quite specific in each area of use.

 

[AngusMcDoon]

I can't understand why plastic boat owners think changing anything is so difficult, as the only drawback to a plastic hull or wooden hull when installing a pair of cooling pipes or plate is the need for them to be attached to the outside of the hull. Installing the pipes in the lead ballast would be better, but a much longer job according to the internal access available to the lead ballast. A bilge keel design is probably the best in terms of installing cooling plates or pipes, as there is no issue over where they can be installed in terms of them not being damaged during a serious grounding.

Tell you what. You do what you want, and the rest of us will do what we want. It's a mostly free country. I'm sure you can install a marvellous system that you like, and most of us can maintain our chosen system to an acceptable level of reliability that we like. If my engine fails, I'll stick the sails up, if they're not up already. It's only an auxiliary engine, after all.

 

[Rappey]

How many hours has your engine done since new, and what do you mean by a high rise mixer ?

God only knows how many miles it did before it went over to hrs in a boat.
My engine is low down in my keel, completely below the waterline.
A high rise mixer has a length of dry exhaust from the engine ,taking it to a cast iron mixer placed above the waterline where the pumped seawater is added and then water cooled exhaust gasses exit via a rubber hose in the usual way. This was fitted because there is nowhere to fit a water box other than above the engine.
My rear engine mounting feet are part of the aluminium adapter plate to allow a hurth gearbox to be connected to the engine.

 

[penfold]

Dry exhausts on yachts are a massive pain in the bum, that's why no-one has them. Keel coolers are largely a non-starter on yachts except steel hulls where a skin cooler can be installed without creating drag or being vulnerable to handling damage.

 

[jwfrary]

God only knows how many miles it did before it went over to hrs in a boat.
My engine is low down in my keel, completely below the waterline.
A high rise mixer has a length of dry exhaust from the engine ,taking it to a cast iron mixer placed above the waterline where the pumped seawater is added and then water cooled exhaust gasses exit via a rubber hose in the usual way. This was fitted because there is nowhere to fit a water box other than above the engine.
My rear engine mounting feet are part of the aluminium adapter plate to allow a hurth gearbox to be connected to the engine.

Sounds like a safe well engineered system trialled by time. Materially nothing lasts forever, but the old school diesels definitely have a lot going for them in terms of reliability.

Personally I think this debate is a little academic, the time of the diesel is over and will inevitably be replaced by electric or sails sometime during the next few decades.

 

[jwfrary]

Dry exhausts on yachts are a massive pain in the bum, that's why no-one has them. Keel coolers are largely a non-starter on yachts except steel hulls where a skin cooler can be installed without creating drag or being vulnerable to handling damage.

Agree, the advantages outweigh the disadvantages that's why it's done the way it is.

 

[Tranona]

I can't understand why plastic boat owners think changing anything is so difficult, as the only drawback to a plastic hull or wooden hull when installing a pair of cooling pipes or plate is the need for them to be attached to the outside of the hull. Installing the pipes in the lead ballast would be better, but a much longer job according to the internal access available to the lead ballast. A bilge keel design is probably the best in terms of installing cooling plates or pipes, as there is no issue over where they can be installed in terms of them not being damaged during a serious grounding.

You really do not have a clue about sailing boats. Not only is there zero advantage of either keel cooling or a dry exhaust - indeed as explained by many others serious disadvantages. It is not a question of finding such barmy ideas "difficult" - simply unnecessary and impractical.

Why on earth would one want exposed pipes outside the hull when you can simply pick up the water through a skin fitting, use it to cool the engine AND exhaust then eject it.

 

[TNLI]

Agree, the advantages outweigh the disadvantages that's why it's done the way it is.

Dry exhaust systems, (For keel cooling), are no big deal if installed when the boat is built, they are a bit of a pain in cost terms if they are done for a suck and spit to more reliable ice worthy keel cooling. The mixing elbow or downpipe will need the hot salt water inlet pipe blocking, the old rubber exhaust pipe will need replacing with an all stainless flexible tube and a silencer box if you want to keep the noise down. The Vetus or other type of water lock will need removing and a new loop water trap installed. Not so very difficult but it will bump up the installation costs.

I like the idea of using my old BMC 1500 for emergency heating, and the attached radiator should provide enough cooling, you will also need a header tank, and I like the alloy ones.
3 Row Aluminium Radiator+Shroud Fan For 1960-1966 Ford Falcon Mustang 5.0L V8 | eBay

2.5Aluminium Alloy Water Coolant Bottle Header Overflow Universal Expansion Tank | eBay

 

[Rappey]

the attached radiator should provide enough cooling,

Hmmm. I run a 25 litre calorifier and have a car heater with car fan yet the engine still runs at 87c. I was initially concerned it would not allow the engine to reach the correct temp.
Would imagine you would need at least 2 car sized radiators with high power fans pulling outside air just to try and stop the engine from overheating.

 

[TNLI]

Hmmm. I run a 25 litre calorifier and have a car heater with car fan yet the engine still runs at 87c. I was initially concerned it would not allow the engine to reach the correct temp.
Would imagine you would need at least 2 car sized radiators with high power fans pulling outside air just to try and stop the engine from overheating.

Sorry I should have pointed out that I have a 35 hp BMC 1500 diesel. Older diesels are a bit less efficient than modern car turbo diesels, so produce slightly more heat. The book figure for a single cooling plate is 0.8 square meters, so I think you will find the combined radiator and fan unit is good for such a large classic donkey.

Can't quite figure out why a radiator & fan unit rated for a 5 litre V8 is not good enough to cool a 35 hp BMC. The V8 puts out around 5 to about 7 times the power!

If you are using a similar radiator and fan with a small diesel and it gets too hot, check that the thermostat is not blocked and that there is no air in the system.