Merc 40hp

[skifforama]

I recently purchased a 95 carolina skiff 16 standard with a 95 merc 40hp 4 cylinder.The boat will not get on a plane and tops out about 10mph or so.I took it to a "authorized Mech." and he did a major tune up with carb rebuild.It still does the same thing.The motor runs fine execpt when under a load.It doesn't seem to get into the upper rpm range,and afull throttle seems to vibrate a little strange.The mech stated it tested fine in the tank, andd was not dropping cylinders,and compression was good.Could this be a prop problem?Anyone know what kind of performance should come from this boat/motor combo?40 is the max rated hp.Any help would be appreciated.

 

[Navigator]

Re: Merc 40hp

Skifforama,<br />Sounds like its over-prop'd. Is the engine reaching the recommended RPM range at WOT ?<br />I would recommend placing a tach on the engine and then lowering the pitch on the prop. 1 inch pitch decrease will gain you about 100 RPM. Determine what your current Wide Open Throttle (WOT) RPM is then do the math to determine what size pitch prop you need.<br />Also make sure your weight is properly distributed.<br />Nav.

 

[Navigator]

Re: Merc 40hp

Oh, I forgot. You should be getting around 30 mph wide open, and about 20 mph at cruise speed. (Give or Take, It depends on your setup).<br />Nav.