Uneven exhaust water flow

[wschneid]

I have an 86 32' sedan flybridge. Both engines run okay. What I notice is there is less exhaust water flowing from my starboard engine than from the Port engine. I have standard 318's. Also, when running above idle speed, I get some grayish smoke from the starboard engine, but not the port engine. Any ideas?

Bill Schneider

[TinLizzy]

Bill, Are you in freshwater or salt? Do you have raw water cooling or fresh/closed cooling? Can you hold your hands on the manifolds and elbows of both engines when the engines are up to temp while idling? When is the last time the impellers were changed? It is always a good idea when changing impellers to look downstream from the pump to make sure that there are not any old impeller blades blocking flow to thermostat housing. Many times people will replace an impeller that has fallen apart and not retrieved all the blades that fell off. There could be blades left over from previous owners that were never removed. There could be rust scale blocking the water passages in the exhaust manifolds and elbows. I had one of the baffles in a muffler come loose and partially block water flow. If it is used in salt/brackish water, the exhaust manifold/elbows only have a few year lifespan. After checking everything over and there is only a slight water flow difference between the two engines, and they are not overheating, you shouldn't worry too much as there is always a slight difference between the two. The smoking engine is another issue. The smoke is more than likely from oil burning. A compression test should tell you if the rings are not sealing as good as they should.

[wschneid]

Rodney,
I have raw water cooling. The boat is in fresh water now, but was in salt water for about a year previously. Both engines run very cool. I will take your advice and check a few things and maybe do a flush on the starboard engine.

[jralbert]

Check the easy thing first: The seal on the intake water strainer. Just a small air gap is enough to throttle the water flow. Sometimes a new gasket is in order, sometimes it's as simple as tightening the cover if it's loose or maybe even apply a little grease or vaseline to the seal .

[javalin390]

I have a similar issue, may be normal. My engines have been replaced, low hours. Rebuilt raw water pumps with the new "Run-Dry" impellers, newer T-stats. New gauges at both helms that are accurate close to each other, so I positive all is well, yet one engine dribbles, while the other flows like a river. May be possible the CCW engine may have something to do with it, don't know.

[jralbert]

...New gauges at both helms that are accurate close to each other, so I am positive all is well, yet one engine dribbles, while the other flows like a river. May be possible the CCW engine may have something to do with it, don't know.

I don't think rotation is a factor. Two items to check: are you sure pump impellers are properly installed - vanes facing the right way? Second, I would take an external temp reading in the vicinity of the t-stat to confirm the gauge reading and to compare with the engine that has much better water flow. And, as in my response to the OP, make sure there's no air leaking into the intake strainer. Happy boating season ahead . . . . . .

[Fastjeff]

I'd puil that impeller and take a look.

Jeff