Marinette Boat Forum

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

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.

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.

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 .

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.

javalin390 wrote: ↑Fri Feb 10, 2023 1:24 pm ...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 . . . . . .

I'd puil that impeller and take a look.

Jeff

I might have a similar issue. On my way home after last summer's cruising around the big lake I had one engine that dropped oil pressure a bit after a couple hours running at 2000 rpm. I slowed down for the rest of the trip and it didn't get worse. In the Erie canal the speed is low and the oil pressure was not a problem. I assumed high oil temperature although I have no instrumentation for that. Raw water cooling, only fresh water.

I replaced the thermostat housing last spring because of corrosion. Big ugly rust scale. So I'm imagining some of the cooling channels plugged with rust scale. Now that it's spring I'll start to troubleshoot this issue. Start with the water pump. Don't expect to find the trouble there as I overhauled it two years ago. Will try to flow water via hose and see what comes out. I can't see the water go overboard when the boat is in the water because I have elbows on the exhaust outside the hull. I'm not reluctant to take off manifolds, but fingers crossed I don't have to pull the engine block.

Are the exhaust manifolds most likely to plug with rust flakes?

Another weakness I have is lack of inlet strainers. The boat has been running all these years without them. Perhaps dumb luck. I assume Marinette never fitted them in the first place. What size strainers do any of you have on a 318 in fresh water?

from my memory bank of experience:
-rust usually (to me) happened gradually and is almost powdery and therefor, flushed as you travel but esp at startup. But, it does flake and that stuff can get caught and build up. One of the places it can clog is the oil cooler. You can disassemble and flush them.
-A cheap laser temp tool can help you spot high temp spots to aid in diagnosing. You haven't mentioned overheating (just oil pressure)so, so far, you're on the good side.
-manifolds have an expiration date. Later in fresh water. YOu can, of course, take them off and check -- after x number of years, you should. And, yes, they can and will get clogged.
-oil pressure gauges sometimes get flaky. You could have a minor gauge problem and not an oil system problem. Check the connections and wiring. If there's no overheating and that low reading is not "extra low", you can relax.-
-intake filter. Came standard on my boat and I think they were Buck Algonquin. I bet you could fashion one out of ordinary screening and a stiff wire or coat hanger.

Thanks for the comments Joel. Visual check of the transmission oil cooler, and backflush with a garden hose if there's anything hung up on the tube bundle, is part of my spring checks. I do find some rust flakes there. In retrospect, I should have checked that last summer after this issue first came up.

The oil pressure never got scary low. I will take my infrared pointer along with me. I could also put a second gauge in for a cross check.