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Old 14-07-2015, 03:45   #16
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Re: Flushing A Seawater Cooled Engine?

Originally Posted by RaymondR View Post
I used vinegar on my 3GM30 Yanmar a number of times. Used a small bilge pump in a bucket with a return hose from the exhaust manifold to circulate it around for an hour or two, appeared to work well from the amount of gunk the vinegar picked up.
Interesting, I wonder if your thermostat had failed in an fully or partially open position.

The raw water cooled GM series don't allow water to circulate though block or head with a closed (cold) thermostat. Well, they allow a very small amount but the bypass hole in the thermostat is only about 1 or 1.5 mm in diameter (1/16"). Nor does water circulate though block or head with the thermostat removed so the only way to flush these engines is to either:

1. Remove thermostat and close off the bypass hose (that's the small -short- hose).


2. Have the engine and flushing agent at normal operating temperature (not easy to do)


3. Have a faulty thermostat that is permanently fully or at least half open.

I don't know but I think that Buhk (and perhaps Beta) engines are similar.

See also
Yanmar GM Series (RWC) Thermostat Alert. - Cruisers & Sailing Forums
Marine Diesel Thermostats: NOT WHAT THEY SEEM - Cruisers & Sailing Forums

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Old 14-07-2015, 09:12   #17
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Re: Flushing A Seawater Cooled Engine?

I flush my Yanmar 3YM30 with a product called SaltAway (Salt-Away Home Page) - I added a valve on the raw water intake just prior to the strainer. To this valve, I installed an 8' length of braided stainless steel washing machine hose that terminates in a female hose fitting. I simply screw in the SaltAway mixing unit that has a garden hose attached and flush the engine by opening the valve and closing the raw water intake through-hull. I guess this hose could also be used in an emergency to dewater the bilge, although the raw water pump doesn't really move that much water volume.

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Old 14-07-2015, 09:47   #18
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Re: Flushing A Seawater Cooled Engine?

Any sort of mild acid will dissolve salts, including vinegar. I would not put HCl in my engine. HCl will dissolve zinc, which is the anodic protection for your engine.


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