Acceptable amount of steam from exhaust

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Briank117
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Posts: 35
Joined: Sun Nov 10, 2019 1:41 pm

Acceptable amount of steam from exhaust

Post by Briank117 »

Hey gang,

While under power (3000rpm), I have steam blowing out both exhaust ports. If I pull back to idle (650+/-), it disappears in about 5-6 seconds. I can cruise all day at 6-10 knot and not see any steam until I throttle up. Temp & oil gauges read fine—and stay consistent. High flow of water out both exhausts—New impellers installed back in spring.

Is there an acceptable amount of steam displacement, or should the boat not steam at all?

(318s raw water cooled. I know the manifolds and risers are dated. Otherwise, motors run great.)
‘74 F32

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prowlersfish
2020 Gold Support
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Joined: Sat Nov 05, 2005 6:56 pm
Location: Lower Chesapeake Bay ,Va

Re: Acceptable amount of steam from exhaust

Post by prowlersfish »

A small amount is not abnormal . Excessive steam is normally due to poor water flow ( even if it looks fine) Risers many times can be at fault . Steam will increase as the temperature drops and the dew point changes .
Boating is good for the soul
77/78 TROJAN F36 Conv.
6BTA Cummins diesels
Life is to short for a ugly boat :D

Boppy
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Joined: Fri Jun 15, 2018 4:01 pm

Re: Acceptable amount of steam from exhaust

Post by Boppy »

I get more steaming on colder days at higher rpms (~3000) from my single 318 rwc engine. Risers are ok, oil, temp, etc all good in spec. Our lake water doesn’t usually warm up until July. I’m usually just putt-puttering around at <2000 rpm and it don’t see much, if any, steaming from exhaust.
‘77 F26 HT Since 1999
Erie Canal cruiser lookin’ for my mule
Great Sacandaga Lake, Mayfield, NY

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The Dog House
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Location: Bordentown, NJ

Re: Acceptable amount of steam from exhaust

Post by The Dog House »

When I bought my 1971 Trojan F26 it had steam coming out of the exhaust. The person I bought it from said it was normal. I changed the impellers any way and it still steamed with the new impellers. I figured it was normal. I ran the boat with steam coming out of the exhaust like that for 7 years.

At the 7 year mark I took in a lot of debris that clogged up the strainer. I shut the engine down when I saw the temperature increasing but the lack of water ruined the water pump. I installed a brand new water pump and had no steam whatsoever coming out of the exhaust. The boat also ran better than it ever had in the prior 7 years. After 45 years of use the old water pump wasn't working fully, even with new impellers and cams. I didn't realize that until I put the new water pump on.

New water pumps are about $700, so its not a negligible cost. My boat ran much better, though, once I put the new one on.
1993 Sea Ray 200 Overnighter OB with 1993 Mercury 150 hp Outboard
1979 Starcraft 14' Rowboat with 2011 Mercury 9.9 hp Outboard
Former boat: 1971 Trojan F26

Briank117
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Posts: 35
Joined: Sun Nov 10, 2019 1:41 pm

Re: Acceptable amount of steam from exhaust

Post by Briank117 »

Appreciate the insight!

I plan to remove/inspect the cooling system over the winter.

I figured the (now) cooler/cold water may have had something to do with it as well.

As always, thanks for the help!
‘74 F32

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