Hi Everyone.
I am in the process of rebuilding my Yanmar YSB 8 ( era. 1986) and I am interested in converting the raw water cooling system to a closed circuit cooling system, to prolong the life of the engine and reduce future maintenance.
I have been looking at a after market Yanmar closed circuit cooling kit for my engine.

ab-marineservice.com/en/product/closed-circuit-cooling-system-yanmar-ysb-8-12/

Does anyone in the Brain's Trust, have experience in a conversion from raw water cooling to a closed cooling circuit., whether it be DIY or buying a kit, like the link above.

I have read threads on other forums, that it is not advisable to install on an older engine that has used a raw water cooling system for many years, as when you introduce coolant to the engine, this will react with the engines internals and flakes of rust and scale will clog the heat exchanger.
Would a good flush with a Metal Gleam dilution clean up the internals of the engine and reduce the effect the coolant will have on descaling the internals of the engine?
I have seen on another suppliers website, that an inline filter can be fitted. This would catch any further scaling and rust deposits circulating the engine.

The other issue is, the kit uses a 12 volt pump and if your battery fails, you could cook your engine. Just another issue you have to keep an eye on.
Do modern day marine engines that work on closed cooling systems, operate a pump mechanically from the engine or are some pumps used that run electrically off a battery, like the conversion kit?

What are your thoughts on converting to a closed cooling system?

If the engine is completely stripped down a strong acid bath for the block should clean it out. Do those motors have cylinder sleeves or are they cast ?

I did this on an old 3qm 30 and it ran too low oil pressure with the elevated operating temp. It was a "keel cooling" system on a steel boat that used the rudder skeg as the cooler. It ran at 80 degrees C with this set up and oil pressure would slowly drop over a couple of hours.
I ended up using void space in the keel as extra cooling capacity and all was good.
Your motor may be different but this one definately prefered raw water running temps.

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BeamReach said..
Hi Everyone.
I am in the process of rebuilding my Yanmar YSB 8 ( era. 1986) and I am interested in converting the raw water cooling system to a closed circuit cooling system, to prolong the life of the engine and reduce future maintenance.
I have been looking at a after market Yanmar closed circuit cooling kit for my engine.

ab-marineservice.com/en/product/closed-circuit-cooling-system-yanmar-ysb-8-12/

Does anyone in the Brain's Trust, have experience in a conversion from raw water cooling to a closed cooling circuit., whether it be DIY or buying a kit, like the link above.

I have read threads on other forums, that it is not advisable to install on an older engine that has used a raw water cooling system for many years, as when you introduce coolant to the engine, this will react with the engines internals and flakes of rust and scale will clog the heat exchanger.
Would a good flush with a Metal Gleam dilution clean up the internals of the engine and reduce the effect the coolant will have on descaling the internals of the engine?
I have seen on another suppliers website, that an inline filter can be fitted. This would catch any further scaling and rust deposits circulating the engine.

The other issue is, the kit uses a 12 volt pump and if your battery fails, you could cook your engine. Just another issue you have to keep an eye on.
Do modern day marine engines that work on closed cooling systems, operate a pump mechanically from the engine or are some pumps used that run electrically off a battery, like the conversion kit?

What are your thoughts on converting to a closed cooling system?

Pump can be easily supported by alternator, regardless of your battery status.
Oxidation deposits can be clean with H3NSO3 (Sulfamic acid) watch your eyes! Is you are scared to use it just use swimming pool cleaner it will do the job.

Good luck!

It would be better to just do a "Metal Gleam flush" once every year or so and keep things simple. Raw water cooled diesels operate much cooler than fresh water cooled diesels. You could change the thermostat but what would be the point. Corrosion in the engine would be internal just like any other engine. The water passages will get blocked by calcium not rust, Freshwater cooled engines get a calcium build up in the heat exchanger just the same.

Select to expand quote

woko said..
If the engine is completely stripped down a strong acid bath for the block should clean it out. Do those motors have cylinder sleeves or are they cast ?

Okay, I will order some Metal Gleam and use it at a diluted rate. The engine has an alloy cylinder sleave, that is still in good condition. I won't use the cleaner on the cylinder. Thanks

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Ramona said..
It would be better to just do a "Metal Gleam flush" once every year or so and keep things simple. Raw water cooled diesels operate much cooler than fresh water cooled diesels. You could change the thermostat but what would be the point. Corrosion in the engine would be internal just like any other engine. The water passages will get blocked by calcium not rust, Freshwater cooled engines get a calcium build up in the heat exchanger just the same.

Okay thanks for the advice. I will order some Metal Gleam and use it diluted, with an annual flush. Thanks

Select to expand quote

stray said..
I did this on an old 3qm 30 and it ran too low oil pressure with the elevated operating temp. It was a "keel cooling" system on a steel boat that used the rudder skeg as the cooler. It ran at 80 degrees C with this set up and oil pressure would slowly drop over a couple of hours.
I ended up using void space in the keel as extra cooling capacity and all was good.
Your motor may be different but this one definately prefered raw water running temps.

Thanks, I will stick with raw water cooling and just do an annual flush of a diluted Metal Gleam, as Ramona suggested.
This should help with the maintenance.

So its about 35 years old now and for how many years will you prolong its life?
Will you still own the boat in 10 years?