Exhaust Steam

[Sixbrothers]

My boat has a 27hp yanmar hmf and yesterday when I went out I noticed there was steam in the exhaust after the engine ran for about 5 minutes. The engine started and ran fine. The alarm goes off and there is normal water flow coming out of the exhaust at first. I only ran it long enough to get back on the mooring. The engine looked fine visually and the oil was fine. Any ideas?

[bubb2]

Raw water strainer plugged, plugged raw water thru-hull. also loose strainer cap she started suckin' air, raw water pump failure.

[L124C]

I don't know how much steam you are talking about, but I always notice some steam when the air temperature drops. After all, you're introducing warm, moist air (exhaust) into relatively dry, cold air. Around here (San Francisco), we call that fog! If it's a lot of steam you should have it looked at. Your manual will also give you several possible causes. Funny story; One night, I was motoring and made the mistake of shining a flashlight over the Stearn to check for cooling water. I about gave myself a heart attack! The small amount of steam looks like a LOT of smoke by flashlight!

[BELLATRIX1965]

I agree with bubb2 - sounds like a raw water flow problem. As bubb2 said, check the raw water system from the suction thru-hull to the exhaust outlet. Also, there is normally an anti-siphon loop in the raw water supply to the wet exhaust. This loop normally has a vacuum breaker at the very top - pull and check that - exhaust soot sometimes plugs these up. Also check the elbow where the raw water is physically injected into the exhaust (follow the hose). This is another spot for exhaust soot and rust to plug the raw water flow. Good luck!