blow by sludge?

[ultrasport]

Hi guys I got the infamous ****ty 470 mercruiser 3.7 liter 4 cyl motor. I have been getting a accumulation of yellow sludge getting into my flame arrestor. It kinda looks like phlem when you u got a nasty cold. Any ideas whats causing this. Ive had blow by before and had to rebuild the motor last season but that was spitting out oil. Also im losing antifreeze but oil is clean no signs of salt water in the oil either. I dont think im losing antifreeze into the motor think its goin out the exhaust (freshwater cooled motor). Any ideas im sooo close to getting rid of this boat due too the continous problems I have with the 470. Any advise appreciated thanks.

 

[CharlieB]

Re: blow by sludge?

What color antifreeze are you using?

Yellowed sludge makes me think of an emulsified mixture of water/antifreeze/oil.

A slight head gasket leaking into a cyl, burning most of the coolant mix and blowing MOST of it out the exhaust but..... allowing a small amount to be scraped down the cyl walls, evaporated and blown out the breather.

Does one of the spark plugs appear noticeably 'cleaner' than the rest, possibly 'steam cleaned'?

 

[ultrasport]

Re: blow by sludge?

Pulled plugs today all seemed to be the same no "steam clenaed" plug observed. All gaskets head and intake manifold are only 1 year old anyone have any advise on where anitfreeze may be entering hte motor. Thanks

 

[Robj]

Re: blow by sludge?

Anti-freeze can be entering by the cam seal. Don't know the exact details, but a leaking cam seal behind the water pump can/will allow coolant into the oil. Hopefully some 470 guys will chime in with more details. I don't own one, never even seen one just read lots about them here at iboats.

Have a great day

Rob.

 

[ultrasport]

Re: blow by sludge?

Any idea on how to figure out how to pinpoint if leak is from headcasket or cam seal, or anyohter possible place?

 

[ultrasport]

Re: blow by sludge?

I changed the oil and did a coolant pressure test. Pumped pressure tester up to 14 PSI as instrucred by the manual and lost 1psi in 10 minutes, ran the boat for 2 hours got a little yellow sludge blowby and lost a little maybe 8 ounces of antifreeze. Did not see any antifreeeze leak during test.
Also changed the plugs. Plug from cylinder #4 all the way at the stern was rusty than all the others. does that help anyone answer what gasket to change. I ordered a gasket kit. Head gasket intake manifold or cam seal? Motor was just completly rebuilt 40 hours ago so hope its not cam shaft seal. Any advice would be great. Thanks.

 

[Mkos1980]

Re: blow by sludge?

I get that once in ahwile. I tested everything and its been perfect. We ruled it as being just condinsation from the blowby then water vapors burning off.