Raw water cooled diesel

[jfkal]

Wan to bounce an idea. My diesel is sea water cooled a conversion kit cost 800 GBP so I had the following idea:

Hook up a t-valve to a hose from my fresh-water tank. Run the engine a minute or so from the tank and shut it off after having flushed out the saltwater. Am I just paranoid or would that add to my engines lifespan?

 

[vyv_cox]

How long do you want your engine to last? I know of raw water cooled engines that have no evident corrosion after 30 years plus. My Bukh has been sold on after 15 years, absolutely no internal corrosion. I believe fresh water cooling to be somewhat oversold and there are inevitable additional reliability problems with the extra equipment.

 

[oldharry]

Inclined to agree with Vyv. I had a seawater cooled BMC that ran just fine, and had done so for years. After a series of YC Bar discussions, invested in heat exchanger etc to convert to FW cooling, and it never ran right again - problems mainly from engine running much hotter than the installation was designed to allow (confined engine space) and with anti freeze in the coolant all kinds of leaks showed up that weren't there before. Always regretted it, and never got it 100% sorted.

 

[RobertMartin]

I am about to start to do the same thing, flush out the salt with fresh water, it has to to good for the engine. I was told to do this by after my engine had a rebuild $5000 later ( oz ). So I am not taking any chances, it only takes 2 mins. I think a conversion is a complete waste of money. More cost, more work, more to go wrong.
KISS. Keep It Simple Stupid...

Good luck

Bobby aka Seawolf..
Sail as if your free

 

[tristan]

Personally, i wouldn't bother with the conversion kit, they provide more trouble than their worth, i would either get an engine with f/w from the start or not bother at all.
That said, there is nothing wrong with just running the engine on salt water as long as 1) the engine has the internal anodes replaced at the appropriate intervals, or is bonded to the ships anodes; and 2) No air is allowed to get into the coolant system when the engine is at rest.

To simplify that, bond the engine negative terminal (or engine block) to the anode, and flush the engine with fresh water at the end of the season when you haul out.

P.S. Even better still, flush the coolant system with a 50% antifreeze/fresh water mix to provide frost protection.

 

[vyv_cox]

I fully agree, except about the antifreeze flush. I have done this in the past and I do believe that it has very positive benefits so far as the engine is concerned. My doubts are over the "once through" method, firstly because it sprays other boats in the area with antifreeze, to the quite possible detriment of their topsides (especially painted ones), but mainly because I'm not sure how well this treatment can coat the interior of the engine. I like the method, seen in PBO many years ago, in which a solution of coolant is circulated for several minutes by catching it emerging from the exhaust and piping it back to the engine suction. This has the great advantage that it also fills calorifier coils, a b***** of a job by any other means.

 

[ArthurWood]

I have raw water cooled 7.4l Mercs and the manual recommends flushing after each use. I don't, but I have fitted Thoroflush (www.thoroflush.com) adapters to my strainers and do occasionally flush for a few minutes. Also useful for backflushing to unblock inlets and for weak acid flushing to remove fur, ie carbonate/bicarb build-up. It's probably pointless to add FWC after the engine has been exposed to salt water as any corrosion will have already begun.

 

[Guest]

doubt whether the approach will achieve anything. when i took my rw cooled yanmar to bits a couple of years ago, it was in pristine condition after 15 years, but it was also slightly silted up with the sand etc that gets sucked through a rw cooling system.

flushing with fresh will not effectively get rid of the salt because of this silting in nooks and crannies. however, i can only second the comment above - after a lifetime in the steel industry, i was astounded at the good condition of the inside of my engine waterways with no evidence of corrosion at all.

find something else to worry about. there always is something on a boat.

 

[ArthurWood]

That's reassuring. Thanks

 

[LadyInBed]

Did it, but for different reasons

I did this on my last boat, but it was mainly so that I could run the engine when the boat was out for the winter and I wanted to do an oil change.
Secondly it was a convenient way of emptying the fresh water tank.
Thirdly it flushed the engine.

 

[jfkal]

Thanks guys. More pros than cons. So I will get the wrench out and do the plumbing.

 

[TonyMills]

Would that it were true for all engines. I recently took off the cooling manifold from my MD7A VPenta and found considerable corrosion (scaling/rust) and am now faced with a significant repair (if its possible). I flush the engine with fresh water in the two years I have had it but I cant vouch for the previous 20 years.

Regards
TonyM