Mercury 4hp 2 stroke, limited RPM's

[Tommyfmu]

We used our Mercury 4hp 2 stroke (new to us) the other day for the first time on our inflatable Zodiac. No problem starting, idling, smoke looked the right color (not blue nor excessive exhaust). Only problem was that while engine should get up to 5k RPM's according to spec, I could only get up to about what seemed to be about 1/2 throttle (or about 2500 RPM's) at WOT.

On an 8 1/2 ft Zodiac with 1 adult and 2 children, we went about 6 knot's I'd guess.

With that kind of load, which seems nominal, should we be going faster and should the outboard be achieving a much higher RPM? I'm thinking that maybe I need to tinker with the adjustable screws, or the compression may not be what it should be.

Thanks for any thoughts on it, Tom.

 

[BatDaddy1887]

Re: Mercury 4hp 2 stroke, limited RPM's

...at the very least try a cup of Seafoam in the gas tank to help clean out the fuel delivery system (maybe check the fuel filter, or old hoses)......also, is that the original prop?

 

[Tommyfmu]

Re: Mercury 4hp 2 stroke, limited RPM's

I put some enzyme fuel treatment in the tank to assist with any possible ethanol problems, and ordered a new fuel filter. It's probably the original prop; doesn't look to be in bad condition, although far from new. All the blades look uniform.

 

[BatDaddy1887]

Re: Mercury 4hp 2 stroke, limited RPM's

OK, maybe a compression test is in order if the filter thing does not work for you. Hopefully, you have the manual for that motor.....