Dave M

I have a 1997 454 Mag MPI. I get more steam out of the starboard side. I guess this is normal?

blackhawk

1995 502 MPI/EFI - I also get more steam from the starboard side, especially on the muffs.

baja bailey

1999 502 MPI, I get more steam from the starboard sid, but usually only in the spring and fall when the water is cooling down...

Revd Up

Well thanks for all the replys. Makes me feel a little better.Maybe there's not anything wrong at all? Just seems like somethings wrong for the starboard manifold to be way hotter than the port manifold. After looking at all the plugs again #4 still is a little whiter than the rest. I checked the water passages and hose to the manifold for problems.I pulled off the top of the exhaust manifold to see if any water was leaking on the inside of the manifold. The gasket had some rust on it on the metal rim on the gasket, but not quite sure if it was leaking. Going to replace the gasket , do a leak down test on #4 to see if the head gasket is ok,but not sure if that will determine that? Put in some injector cleaner, switch spark plugs from one of the richer cylinders to #4 and see if it is the plug. Any other suggestions?

HARRISONMIRAGE

If it's reversion it will go away if you rev it up to about 900 rpm.My cam makes my motor suffer from reversion but only at idle.I can tell from the steam.I figured this out by removing the risr and finding water pooling n the manifold.Most motors have reversion without there owners being aware of it.

Steve_H

scarab22 , any news?

J-Bonz

How old are the exhaust manifolds and is it ran in salt water. it could be just rust build up in the water pasages of the cast manifold. if i remember rightly they roughly go around 10yr for fresh water and 5ry or earlier for salt water

good luck,

Jack

blackhawk

scarab 22, I was unwinterizing my boat 2 years ago and running her on the muffs and I realized there was a lot more steam coming out the starboard side. Starboard mainifold also was much hotter. I was worried sick that something was wrong to the point I wasn't sure if i wanted to take my boat out. I finally did and it ran perfect. I guess I never noticed the starboard side running hotter until that year.

I think your only concern is finding out why #4 plug is leaner.

Tim G.

I have the same situation with one of my motors...
I have gone through all the obvious things, and I have figured out that I have an air leak somewhere between the bottom of the drive and the water hose from the transom plate fitting....

Is your motor pumping a lot of water out the pipes??? If not, you're just lacking water.
Try thins- Pull the 1 1/4" hose off the TP fitting. THen insert a garden hose and clamp it on. Start it up...
The sea pump should have enough suction to try to squeeze the garden hose shut....and you should have a lot of water flowing out the pipes.....
That's how I figured out my problem....
Now I just have to find the actual leak.
I'm going to put the water through the drive and plug off 1/2 the pickups to increase pressure.... that should show me the leak.......I hope...

Revd Up

Tim G, That sounds like a good idea. I'll check into that next and see how much water i'm pumping. I checked the compression and it was fine, so I don't think its a head gasket, also it would run bad which it doesn't. Had a couple of other people look at my lean plug #4 and they didn't seem to think it was that bad. I'll keep an eye on it. I changed the exhaust manifold gasket. The one between the elbow and the log. I think it was leaking on the inside between the water jacket and exhaust . It was rusty and some pitting. The original gasket is metal and only about 1/8" thick between the water jacket and exhaust. Merc. has now changed that gasket to a non metal one, and it's about 1/4" thick between the water jacket and exhaust port. It's been raining alot so I haven't had a chance to try it out. Hopefully in the next couple of days.