Inboard motor, steam coming out exhaust

Manifold/risers are a possibility, but check easier possibilities first.
Weak water flow can be caused by weak impellers, clogged water intake, dirty/clogged sea strainer, obstruction somewhere in the the raw water circuit (transmission cooler, oil cooler, fuel cooler, primary heat exchanger).

My first steamy exhaust experience was caused by two broken fins on impeller. I was still getting a lot of water out of exhaust at idle and didn’t have engine overheat. Changed impeller (discovered two missing fins), back-flushed transmission cooler (found the missing fins), problem solved.

After that I bought an IR heat gun and now check my engine and exhaust system for hot spots regularly.
 
He said thanks for quick reply. I also told him get the heat gun before he does anything. Really helps narrow down the issues.
PS not overheating yet, but he knows something not right about that steam and wont go far til fixed, trying to get a mechanic now is impossible.
 
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Steam is not uncommon. Exhaust temps reach 400+ and mix with water, thus creating steam. Temp/dew point spreads also help in making steam more visible.

My engines produce steam on occasion. No problems with impellers, water flow, strainers, manifolds, etc. All engine temps normal.
 
When I had my inboard I had steam out of the exhaust when I bought it. The PO said it was normal. I changed the impellers and the cams. It still steamed so I thought it was normal. Several years later the water pump failed and I had to replace it. With the new water pump there was no steam whatsoever.

How old is the water pump? If the water pump is more than 25 years old it might be time for a new one. My engine never overheated with the old water pump but it obviously wasn't performing up to spec.
 
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We have owned four boats with inboard motors, all purchased new. Each one of them produced steam from the exhausts from the time they were brand new and went on to enjoy long trouble free lives. Steam is normal. Wear items like pumps occasionally wear out and need to be replaced, so having a pump fail while having steamy exhausts is nothing more than a normal occurrence. The important thing is to perform PM on a schedule recommended by the supplier of your equipment. Most of the problems people post about on these boards about leaking lines, rust, gennys and engines not running properly are the results of deferred maintenance or no maintenance. You spend less money in the long run by following recommended schedules. Also, your down time is planned and you have more fun on your boat when you keep up with preventive maintenance.
 
So if there's white steam but no overheating, should I be worried about it?
 
superwa said:
So if there's white steam but no overheating, should I be worried about it?
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Steam is quite common when the mornings are chilly etc. usually, as mentioned above, water flow can cause this to happen. I had a 340 that always threw steam, engines were perfect and ran great - never even a little hot but always steam.
 
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Another item to inspect are the gaskets at the ends of the heat exchanger. They will deteriorate and obstruct the internal tubes of the exchanger restricting its flow. (Item #33 in the drawing)
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SKybolt said:
Steam is quite common when the mornings are chilly etc. usually, as mentioned above, water flow can cause this to happen. I had a 340 that always threw steam, engines were perfect and ran great - never even a little hot but always steam.
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Same with my 340 and it's got new 8.2 Mercury big block engines. The colder the water temp the more steam I find.
 
Add a +1 to "normal"

I had a 310 and now a 380, both with inboards. Both steamed like a mofo, most if not all of the time, but some times worse than others and usually one side worse than the other (although I never cataloged whether it was the same side). Have always changed impellers regularly, and the 310 ended up having both water pumps replaced, no difference.

If it's running well, no worries in my opinion.
 
One thing that seems to be missing in these good responses, is there water flow with steam or no water flow or limited water flow. My 1989 Pachanga with T350's steamed a little all the time but there was always good water flow out the through hull exhausts and no overheating. You didnt say, that I see, what the power system is - Assume since you can see exhaust its a through hull so you can gauge water flow from before to now. If good water flow with minor steam/no overheating after 3,500 RPM runs for extended period, as others have said, no problems. On the other hand, if flow drops, steam significant, slight to moderate heating, yes, likely a problem and look at areas noted above. Couple other notes - For Bravo III's and Alphas, its recommended to change cooling impellers every other year or at least inspect during winterization or dewinterization. I suspect the same for Bravo I and II's as well. Getting Hardin Marine SS housing/impellers can extend inspection to maybe 4 year but still should replace regularly. Regarding normal temps - Big blocks seem to run hotter - say 180ish while small blocks should stay around 165ish. Check oil filter housing with that temp gun as well as risers to get additional information to the idiot gauges on the dash (or better with newer boats, more reliable vessel view). Faria gauges are notorious for being off when they get older.
 
To further confirm steam is normal. Last year I:

Installed new exhaust manifolds;
Installed new exhaust elbows;
Installed new seawater pumps;
Installed new seawater hoses;
Installed new wet exhaust hoses;
Installed new gaskets on the engine heat exchangers;
Rydlyme'd the seawater cooling system.

......and I still got steam.
 
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