no top speed

[chickster]

I have a 2004 G-3 with a 40hp yamaha 4stroke. maybe 50 hrs on engine. When I first took it out, i could reach maybe 32-33 mph. Now I'm lucky to hit 20mph. My son says he hit something when he used it. Iv'e checked the prop shaft and inside the prop spline.it all looks good. My tach will read 4500 rpm'sbut no go. Any ideas?

 

[rodbolt]

Re: no top speed

what was the top RPM when first installed ?

 

[jaymasta]

Re: no top speed

4500 seems kinda low, I think you should be between 5500-6000rpm, but I could be wrong, what does it stated in your manual?

 

[Ray Neudecker]

Re: no top speed

Since your son says he hit something, I would look toward the prop pitch having been changed by the accident. 4500 is too low an RPM for this motor and would be considering a prop which let it turn in the 5600 range.

 

[Silvertip]

Re: no top speed

Although 4500 RPM is about 1000 RPM short of its WOT RPM, before spending money on a prop, you need to determine what changed. A prop strike could mean a partially sheared flywheel key which throws off ignition timing which may limit WOT rpm. Since it ran ok before, blaming the prop is not rational unless physical damage is evident. Lots of things to consider here.