Does this sound right

[PowerAddict]

I had the gps out today. And I was looking at my MPH at WOT.

a merc 140, 16' Tri-hull, With a 17p prop I'm only getting about 4000RPM about 4250 if I mess with the trim. and a top speed of 34-36 mph.

Does this sound right? Shouldn't I be more at like 4500-4600 rpm w/ this prop at about 45?

 

[Fireman431]

Re: Does this sound right

What year is the Merc? My manual doesn't show a 140hp. The 135 & the 150 both have WOT RPM @ 5000-5600. Start with a tune up and then begin adjusting trim or prop. Make sure the engine is firing on all cylinders and verify with a quality tach. The older tachometers get, the more aberrant they become.

 

[Fireman431]

Re: Does this sound right

I just re-read your post. I have to assume it's a 3.0L (135 hp). WOT is listed as 4400 - 4800 RPM. Again, start with a tune up.

 

[PowerAddict]

Re: Does this sound right

my manual says 4200-4600

Its got new plugs, condensor, cap, rotor etc.

But I thought it still didn't seem right. So I do think its the old gas. Probably go for a carb rebuild too.