2001 Merc 350 Mag MPI White Smoke

Joe Poznanski

Joe Poznanski

New Member
Nov 16, 2018
2
Boat Info
2001 SeaRay 280 Bowrider
Engines
2 x 350 Mag MPI w/Bravi I Outdrives
Lets start with a background. I bought the boat in March 18' and I noticed there was a small amount of white smoke coming from the starboard engine. It ran and still runs great, but the white smoke has intensified. This intensification occurred in a matter of two outings. This occurs from start-up to when I return for the day. It leaves a sheen in the water which makes me think it is gas. There is no white smoke coming from the port engine so that rules out water in the gas. Plus, I just changed the fuel filter and there was no separation/debris when I poured it into a clear bottle. The compression is high in all 8 cylinders ranging from 180-193. There was soot on all 8 spark plugs which affirms the no water theory. This makes me think it could be a cylinder that isn't completely combusting all the fuel. How do I figure out which one it is?
 
Have you changed the plugs,wires and dist
Cap lately?
 
White is steam from water. Soot on plugs would be blackness out exhaust. You may have 2 issues here.
 
Compare the plugs - google "how to read a plug". If there's a difference in how one cylinder is operating, there will most likely be evidence in the way the plug looks.

Do the engines have closed cooling?
 
Hey guys thanks for the feedback. I just changed cap, rotor, plugs and wires. Also changed MAP sensor. I still have white smoke. Might take it to a local marina...idk what else I can do
 
Good compression on all cylinders and normal amount of soot on the plugs tells me that the cylinders appear to be ok and not ingesting water.

This could possibly be clogged manifolds and/or riser, creating hot spots where exhaust water boils instead of being pushed out as a liquid.

How are your manifold and riser temperatures?
Can you keep your hands on he risers or are they too hot?

Another possibility is a cylinder head crack in the exhaust port. Cooling water could be entering the exhaust stream at a very hot area.

I would remove the manifolds and take a look at the exhaust ports.

You still haven’t answered the fresh/raw water cooled question.
 
White smoke tells me water. A leak down test will tell you if you have a head gasket problem. If so then there is your answer. As others have stated the issue could be downstream from the engine.
 
That doesn’t explain why it only happens to one motor and not the other.
 
You must log in or register to reply here.

Forum statistics

Threads
113,154
Messages
1,427,354
Members
61,060
Latest member
Danileo
Back
Top