Steam from exhaust
 

Had the boat out today and noticed one side of exhaust was running a little hot? Steam coming from exhaust. Other side is cool. 1999 502MPI. I"ve seen other posts about this, but can't remember?. Is this reversion? Stock Merc. manifolds. Pulled the plugs and # 5 is white. The rest are tan. What do I need to do to fix this problem?
Thanks,
Steve

Re: Steam from exhaust
 

How is the impeller in the sea water pump?

Re: Steam from exhaust
 

It was my experience that the port side exhaust runs hotter than the stbd. It is in the design of the merc cooling system in how the water is routed to the exhaust manifolds. The #5 and #7 cylinders are next to each other in the firing order and usually run hotter than the rest, but if it is white, you may need to check the injector and or fuel pressure. The factory setup is on the rich side and I almost always had plugs on the dark side from running so rich.

Re: Steam from exhaust
 

The impeller should be alright, as I checked it about a month ago and it looked good. The #4 cylinder is the one running hot (sorry typo) . Port side cool, Starboard side hot. Any suggestions ?

Re: Steam from exhaust
 

The water has two ways out of the engine...the right side or the left side. Water will take tha path of least resistance , sometimes leaving one side drier (and steamier) that the other :( . I've seen quite a few that have this situation , particularly at an idle when you one have a very small amount of water pressure. When running the pressure comes up and the flow increases out of both sides barring any major obstruction.
As others have stated , #5 could be fuel. Unfortunately , the one time I saw it it was a bad head gasket allowing a small amount of water in and steaming the plug and combustion chamber clean :mad:

Re: Steam from exhaust
 

How do I check to see if head gasket is leaking?

Re: Steam from exhaust
 

couldnt it just be cold lake water temps?

Re: Steam from exhaust
 

The water was cold but I don't think that is the problem. The starboard exhaust manifold was hot to the touch. Port side manifold was cool. The white spark plug on #4 cylinder is what has me concerned. I'll do a compression test on #4 in the next couple of days and see what that looks like.

Re: Steam from exhaust
 

Upon further thought I think I was wrong on which side runs hotter. If you can put your hand on it without burning it is far from running too hot. Especially with cooler lake temps, steam doesn't surprise me. #4 running lean is another issue. Hope you get to the bottom of it.

Bill

Re: Steam from exhaust
 

I have a 1994 502 mpi and I havn't noticed a temp difference but my #4 is always clean compared to the others. I havn't figured it out yet. I just changed the plugs last week, I have a lean condition across the board but I will adjust that with fuel pressure.

Re: Steam from exhaust
 

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

Re: Steam from exhaust
 

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

Re: Steam from exhaust
 

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...

Re: Steam from exhaust
 

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?

Re: Steam from exhaust
 

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.

Re: Steam from exhaust
 

scarab22 , any news?

Re: Steam from exhaust
 

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

Re: Steam from exhaust
 

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.

Re: Steam from exhaust
 

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...

Re: Steam from exhaust
 

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.

Re: Steam from exhaust
 

TimG'
I had a problem like yours and it turned out to be a piece of wood lodged in the rubber hose going thru the transom assy. It got jambed thru the LWP on the front of thr drive. When back flushing with the drive removed , full hose pressure had the water hitting ground about a foot behind the boat. I added 150 psi air thru a T connection and tried again , now the water was hitting ground about 3 free out and my temp problem was gone :cool:

Re: Steam from exhaust
 

scarab22 , do you have silent choice?
could there be a problem with IT maybe?
reason im following this thread is i have the same warm on one side , hot on the other with both my 502 efi's. pulled one impeller last night and it looked fine. i also have very little water coming out of my exhaust on one side.
same situation on the other motor but very little water out the opposite side.
motors never overheat but i get steam like you.
im going to try Tim G's garden hose trick also and see what i get.

Re: Steam from exhaust
 

Yes, I do have silent choice and its works perfectly so I don't think thats a problem. I'm also going to try and do some back flushing , and tighten up hose clamps in case I'm sucking air.
J-Bonz, the manifolds and engine have very low hours and are run in fresh water.When I took off the exhaust manifold elbow, I checked inside, looked good.

Re: Steam from exhaust
 

Well, now that we're in the off season I decided to do some checking. Followed the water flow and found that my impeller was bad, even though I had lots of water out the pipes and running 180 on the temp guage.( ran one time in some shallow water, sand/gravel bottom) Also found some impeller chunks, seaweed, sticks,and a small rock all stuck at the entrance to the oil cooler!.This should cure my problem. I still think it will steam more out the starboard side though. Merc says it normal. :rolleyes: