Marinette Boat Forum

I too have a white smoke/steam that comes out the exhaust ports. Only happens at faster speeds - above 2000rpm. Seems to dissipate quickly.

Lots of water shooting out. I shot various parts of the manifolds/elbows/exhaust hoses with an infrared laser thermometer. Everything reads between 95 and 140 degrees. (coolest areas were tops of manifolds, hottest areas were elbows)

Engine temps read slightly below 160 on the gauge while we are at cruising speed.

With everything seeming to run so nice and cool - any ideas? Am I dumping water into a cylinder? Engine has run great since the day I bought it 2 years ago. It has always done this steam/smoke at higher speeds, I just never knew it was a potentially major problem.

Link to video of this problem: https://www.youtube.com/watch?v=Xj1F0QTuOCA

THANKS!

My boat did that crapola for years without a problem--especially at this time of year (cooler water temps). I know it's a concern, but you temps are spot on.

Jeff

What was the air temp during that run? To level set your concern, my engine was doing it on a 80-90 degree day with water temp in the 80's. I almost think mine was boiling water. Both engines and genset would produce steam on a 65-70 degree day/night.

Thanks guys, your wisdom is always appreciated.

Air temp was about 65 degrees that day with water temps slightly warmer around 69 degrees.

I do know that several of the baffles in the mufflers are dislodged. Not sure if that would have any affect on this.

Ever notice on a fall or spring day when the air is cooler than the water and we have fog around our lakes, rivers and swamps? Your boat does the same thing when it dumps warm water and exhaust out into cool air and cool water....The colder the temps the more steam. Example, labor day weekend I left Bayfield Wi and headed out around the perimeter of the Apostle Islands, as we got out around the outside of the islands where the water was 100' deep or more and much colder(15-20 degrees less lake temp) there was more exhaust steam, coming back inside the islands as the water got warmer=less steam. Don't worry about it too much in these cooler fall temps and cool water temps. Steam in 80 degree water and aor temp, different story.

My 1986 has twin 318's. Yesterday, one produced white steam. The other one didn't. The one that had the steam, had the big muffler felt a bit warmer to touch. If outside temp was 75, water temp around 80, shouldn't matter if one engine had steam, and the other one didn't. I usually run engines around 1500 rpm, and they ran good without overheating.
I would like to know what causes the steam.????
Thanks in advance for any comments.-------------
__________
Capn Gary
1986 32 FB twin 318's 1875 hours
Milton, Fl

I seem to recall the same thing and never found out why. You could check actual temps with an inexpensive laser thermometer. They are generally quite accurate. Measure at various points along the exhaust system...keep some notes.. and compare betwn both engines

Mine did that as well at times--especially when the weather was much colder.

As Joel said, you need to check everything over with an infrared temp gage. Start at the temp sender unit (front of the manifold) and shoot the brass body. Next, shoot the exhaust manifolds (anywhere on them) and compare each one. If you see more than 140 degrees on the manifolds (at idle) something is amiss. And if one is MUCH hotter than the other, that too is a problem (which I can help you solve).

Good luck.

Jeff

Possibly unburned fuel vapor. Does your exhaust smell rich?

No, it's steam. Very common in colder weather.

That said, you need to verify the operating temps of your manifolds with a infrared temp gun.

Jeff