1986 50 Hp Merc fuel issue

[sd7088]

I recently bought a 1986 Mercury 50 Hp, started out starter would not work but found the neutral safety switch cable was broken, next I took to a lake and it would accelerate to less than half throttle at wide open and bog. Seemed like its a gas issue so I replaced all the hosessss and it is better but still nothing over half throttle,should I start by cleaning crbs? It idles and starts with ease, leading me to main jet, any advice?

 

[gm280]

Well first things first sd7088. :welcome: to iboats. Nice to have you aboard...

Okay so it bogs at WOT or less. I have to agree with your assessment that it is a fuel delivery issue. And yes it can easily be carburetor too. But you can eliminate other things before removing the carb for an overhaul. Remove the fuel line from the fuel pump at the carb and see if the fuel pump is working properly. If it isn't passing fuel through at a good rate, you could be starving for fuel and therefore not allowing the engine to go... If your fuel pump is working properly, then it is time to remove the carb(s) and completely disassembly the carb and use carb spray and compressed air and verify all holes and slots in that carb are open and clear. And that means every hole and slot. So you have to remove the jets and needles and such and clean it well. Then install a carb kit and reassembly and install again. That should solve your problems... :thumb:

 

[sd7088]

gm280 to check fuel pumps take the 4 screws out and see if fuel flows similar between the 2 of them? Thanks

 

[Bill kubiak]

Just remove the fuel hose from the carb to see if the pump pushes fuel out when you crank it, do not remove the fuel pump........yet

 

[sd7088]

Bill, took a look at motor, there is no fuel pump on it like my dead 40hp merc, just gas line from connection to filter to the T where it feeds the carbs, am I blind??

 

[Bill kubiak]

Gotta be a pump

 

[sd7088]

I agree! Only thing I see is 2 rectangular shaped deals on carbs but my 40 has them too, and it has a pump on that. I must be blind!

 

[Bill kubiak]

Most pumps are square and bolted directly to the intake manifold

 

[mixerjv]

If it's the 4 Cylinder classic 50 the fuel pump is integral to the carburetor! But before that, are you using the new EPA mandated controlled vent tanks? I had the same problem on my '85 Mercury 50 and switching to old tanks solved the problem.

 

[Bill kubiak]

The EPA causes more issues then it solves, gotta keep those people all working making up new rules all the time
I think the EPA just turned a river orange the other day

 

[sd7088]

I was using the older style steel tank with the vent in the silver cap,yes it is the classic 4cyl 50, pumps must be under the blue caps on side of carbs

 

[mixerjv]

Yes the pumps are under the blue caps, and there is no way to test the fuel pump pressure on those engines. I would say a full tune up is in order, link & sync and carb rebuilds. If the ignition wires have never been replaced, it's time. I had a hell of a time with ethanol and the floats on those carbs in particular, it would make the floats stick. When you do the carb rebuilds, be very careful with the "ears" that hold the little rod that holds the floats (I ruined a perfectly good carb by breaking an ear)

BTW you have a great engine. It started as the Mark 58 in 1958, become the Merc 500 in 1961, became the Classic 50 (45) and ended it's life in 1995 as Mercury 40HP. Plain vanilla crossflow, when tuned right idles comparable to any electronic modern engine.

 

[sd7088]

is it possible when I hauled it on its side that a carb float jiggled out of place? Or other thought some dirt blew into carbs, that seems unlikely compared to float,