I'm observing whisps of "steam" coming from my exhaust. More at WOT than at idle. Boat is BBC, raw-water cooled with thru-hull wet exhaust (stock Mercruiser manifolds/risers). No visible problems exist and water temp is OK.

How much steam is acceptable?

Thanks in advance,

D. Ocean
Pompano Beach, FLA

How does one see whisps of steam at WOT? Seems like it may be hard to detect. Plums of steam maybe, whisps, no.

BT

There should not be much. Replace your sea water pump impeller first. If that does not fix it, you may have an issue with the exhaust risers.

>There should not be much. Replace your sea water >pump impeller first. If that does not fix it, you may >have an issue with the exhaust risers.

The exhaust risers are old. What kind of "issues" might they have?


>How does one see whisps of steam at WOT? Seems >like it may be hard to detect. Plums of steam maybe, >whisps, no.

Well, "plume" isn't how I would describe it. "Whisp" is more like it.

D. Ocean
Pompano Beach, FLA

riser issue are leaks.

water leask back down into your engine and can cuase it to eat itself. Thats not good.

if you see any water weepign fron teh manifold or riser on the outside you can bet your ass you have leaks one the inside.

replace with soe kind of aftermarket manifodl or header. Stock merc manifodl are notorious for leaking and premature failure.

I get a lot of steam out of my starboard side after a hard run. It lasts a minute or two and then starts to dissipate. I added lightning headers last year as well and had the steam with stock manifolds. I also put in a new impeller and still have the steam. It seems to be fairly normal?

Another problem with exhaust and risers is they can become clogged by the iron scale from the corrosion process. This will restrict the water flow and cause hot spots which could create steam. Sometimes you can detect this externally by feeling the "firmness" of the water hose that feeds the exhaust while the engine is running. If it is hard, you have restriction and the exhaust needs to be serviced. Scale and corrosion is removed by soaking the manifolds and risers in muratic acid, rodding out, soaking again, then flushing with fresh water.

BT

My bet is that your risers gaskets are leaking.

I was seeing a lot of steam with my Gil Exhaust and both manifolds had internal cracks.

Thats normal. If the exhaust steams on start up or while running and the water is not real cold, look for cracked head. Found out the hard way.

After you check the manifolds and risers of course