Mercruiser 7.4/330hp -98 Gen VI

I winterized my engine in the end of september and pulled it out the boat and put it in my garage in the middle of october the winter didnt get here until end of november so it shouldn't be a problem.

This winter i have just done the ordinary things, new oil and filter and of course a new fuelfilter. I have also changed all the belts and pulled my carburator appart and cleaned it. I almost forgot that i put new sparksplugs in.

The not so ordinary things that i have done is to paint the manifold, risers and thermostathouse with new color and i have also checked that the torque is right on the rocker arms.

I pulled the engine back in and went for my first ride last week, it went great, in the beginning.... The boat started emedietly and i sounded really good. We went for a ride for like 10 minutes in the range om 3000-3500 rpm and for a short time we were pinnin ut up to 4500 rpm. When we got back to the docks i noticed that i had white smoke blowing out from the port exhaust.
I felt on the risers and the water comming out from the exhaust system and it was hotter than the starboard exhaust.
I looked at the water tempgauge and it looked allright, just about 150-160f. I let it ran for a while at the docks and then suddenly it stopped smoking.
I pulled it out from the water, changed the thermostat, impeller and pulled of the risers and manifolds of and they looked great, pulled it back with new gaskets AGAIN. I filled the engine with water from a hose so there are no stops in it. I also pulled the circulationpump apart and it works great.

Put the boat back in the water, SAME PROBLEM! Pulled it out, did a leakdowntest today and all the cylinders is between 7-9%.

I dont know what to do, the boat runs great but when it gets hot it starts to come white smoke from port exhaust and the water comming out from the port exhaust is much hotter than ond the starboard side.

Please help me!

I forgot to write that i have also checked the ignition timing.

How cold is the water you are running in?
Maybe there is nothing wrong. Just that your thermostat doesn't get warm enough to open all the way and at lower block pressure, the path of least resistance is the tsarboard side. Or something limiting the flow on the port side.

I wouldnt think its that abnormal if on engine runs a little hotter than the other. All the boats ive had always blow white smoke, just depends on how much white smoke if its a bad thing. Just keep an eye on things, after sitting for 6 months any engine going to act funny make some weird noises etc. Just take it wasy for a while, keep an eye on gauges

I wouldnt think its that abnormal if on engine runs a little hotter than the other. All the boats ive had always blow white smoke, just depends on how much white smoke if its a bad thing. Just keep an eye on things, after sitting for 6 months any engine going to act funny make some weird noises etc. Just take it wasy for a while, keep an eye on gauges

Mine also has the "white smoke" sometimes. I'm sure its just steam and nothing to worry about!

Is it steam or smoke. My port side steams a little after extended cruises but eventually goes away after idling a minute.

on the thermostat housing where the hoses go to the manifolds,when you remove the hoses their should be 2 plastic balls with a rod going through them with little springs forcing the balls twards the water hole..sometimes those springs rust out and don't apply pressure to the plastic balls..i would start their,if all looks good then you may have to apply a little more pressure to the plastic ball so it will equalises the pressure of the water coming out..

I don't think he has twins, he is referring to the port side exhaust(left exhaust manifold)

I am guessing it is white steam and not smoke. It is steaming because that side of the engine is running hotter, I would check a flow restriction somewhere in the cooling system

If I run in cold water 40 - 50 F I get some steam out of the exhaust. It's nothing to worry about. I have also noticed that it can be more noticeable on the port side. When water temps come up in the summer, I don't get any steam, unless it's after a long hard run. As long as you dont have water in oil, or other issues, I would not worry about it.