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1986 45hp Mariner 2cyl power only

guido2

guido2

Regular Contributor
This was running good last season. First thing this season had water contaminated fuel run into it. Owner had bad fuel cap on his pontoon boat. I replaced fuel tank and hose with fresh fuel also new spark plugs. Forced fresh fuel through carbs while engine was tilted and then started ok. Running on only top 2 cyls. Spark very strong on bottom cyls but no power and will not idle. Good compression on bottom 2 cyls but only the #3 cyl showing a wet plug with fuel mix. #4 cyl drier?? Don't see why because lower carb seems to be providing fuel. Any ideas? Thanks, Guido
 
The lower reed block could be gummed up - it feeds cylinder 3 and 4. Unfortunately, this model has the reeds on the donuts on the crankshaft, so even with the carbs pulled you can barely get a glance at them.

However, since you really shouldn't run it if cyl 3 is getting less than a full fuel/oil/air charge and cyl 4 doesn't seem to be getting any at all (that flowchart leads to two toasted cylinders in short order) you might try cleaning the reeds without totally tearing everything down.

I would pull the bottom carb off and really dose the intake/reed block (like I said, you can kinda see the reed block with the carb off and you "visualize" what you can't see) with either Merc powertune or gumout (or something similar) - let it soak in good and then give her a try again.

But if you are certain the lower carb is fine, the reeds are about the only thing standing in the way of the fuel getting to the cylinder properly. And that normally means splitting the block to get at them...
 
Hi just returned from our cottage in remote Ontario, thanks for the info. I'll try your idea. Take care, Guido.
 
I seriously doubt there's anything wrong with the reed valves. It sounds like the lower carb is plugged and needs cleaning. That said you should check the lower cylinders for spark.

Jeff
 
Yeah thanks, that was the problem. The owner had another guy work on it. It runs on all 4 now. I was out of town and told the boat owner what you said the problem was, which only confirmed what I had suggested originally. I checked the guys work and it seemed ok at first, but the motor will flood on restart. Seems running rich on lower carb. I think the guy cleaned both carbs cause the wire hold down tab for the trigger was hanging loose and not fastened to the upper carbs port side stud. My guess is that he either set one or both floats too high and/or he didn't replace the float needles. The boat owner is 76 yrs old and I think he wasn't there to see the repair. The mechanic charged him $100 and worked right over the back of the pontoon boat while floating in the water.
What would you suggest I do? Get involved again and fix it right, or suggest to the other mechanic to give it a better job? The owner still owes me for my new OMC steel gas can and labor to flush out the water from the fuel system, then replace spark plugs. Its a 20 mile round trip and I have been there 3 times now. Its tough when another guy gets involved in your job.
Thanks, Tim
 
My wife constantly shides me for "not looking!" and here I did it again! Totally missed that your motor is a 4 cyinder running on 2 cylinders. (It's NOT a Yamaha!)

Seeing you have nice spark on those lower cylinders, you are correct that the carb is flooding. A simple cleaning job should cure that UNLESS it's actually a torn diaphragm in the fuel pump.

Note: A dribble leak from a carb is common; a flood of gas leaking is not. Which is it in your case? If it's a dribble, replace the fuel pump diaphragm.

Jeff
 
Sometimes its a dribble and other times a flood. Seems its dumping in while the motor is turned off so its flooded when you go to start it. Could you pls review my last question again? thanks, Tim
 
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