Rust in thermostat - cold engine - >> how to flush engine

[ditri]

Hi. I have 96 Mercruiser 3.0 lx. After cruising i have the small pieces of rust in thermostat which caused that the termostat is still bit opened and the engine is runing cold. I must clear the thermostat again And again..... And boat runs in normal temperature. It looks like somewhere in the block is something corrodet. Is here the way to clean it And prevent it? Thank you for some info...

 

[Scott Danforth]

clean it - yes, however not easy.
prevent it - not without buying a new motor with a heat exchanger

are you boating in fresh water or salt water?

 

[ditri]

Hi. Im boating both waters. Sea and river. I see that there is chance to buy heat exchanger but as i read its not good to buy it for old engine.

 

[Scott Danforth]

Correct, the rust your currently finding would plug up the heat exchanger. Heat exchangers should be put on new or low hour fresh water only motors

 

[alldodge]

If the boat hasn't been used in a while the corrosion may have built up. So long as there is not large chucks of stuff just keep running it and it should flush out the loose stuff, will just take a bit of time.

 

[ditri]

Hi. Thank you so much for the answers. But i have about 30 days of cruising this year and the small bit of corrosion still fills up my thermostat. Any chance to clean it for the next spring?

 

[alldodge]

I know of no easy way, the biggest problem is how to flush a lot of water thru the block with only a small hole to drain it out of. To have so much corrosion you must be in salt water, and that is causing the issue. If the thermostat was left out for some runs it way flush most of it out, the issue is the block having a small space to trap particles.

For next spring get all of the salt out by flushing the block with thermostat and drain plug removed.

 

[ditri]

Hi. Thank you so much for your answers. I must clean the thermostat this whole season. The corrosion flakes are very thin (the bigger should be 0,5m) and it looks like there is some thin film of corrosion in the engine. It is very frustrating to remove thermostat before every ride and clean two micro pieces of rust from them. Please is there any way to flush the engine before winter and remove this corrosion film? I m thinking about make some flushing with citric acid etc and let it circulate for some time in engine. The old cars fanatics uses many types of flushing from coca-cola to some acids, vinegar etc...if it is marine engine there is no problem put some tub under the leg and let the flushing fluid circulate through syst?m. Yes it must be good for Alpha leg, gaskets etc...

 

[alldodge]

IMO, stuff that can clean the block out can also damage the rubber seals. Its never a great idea to run the motor without the thermostat because it will can carbon up from unburned fuel, but can be done.