I can’t figure out why at WOT my boat isnt pushing but 3100 RPM’s?!?! Everything I’ve checked so far is good. Timing good, fuel delivery is good. Fuel pressure is good. Prop is 14.5x21. It runs great and pulls great but I should be getting more than 3100 rpm’s and 35 MPH. Im clueless on what it can be. Anybody have any ideas???

Boat is a 2005 stingray 180lx

I did some quick math and with reasonable slip numbers it seems you have a 1.5 drive, which means you are WAY overpropped. Is this boat new to you? Can you verify the drive ratio?

Yea it’s new too me, 2 years. The outdrive ratio is 1.97

Is that GPS speed or speedometer speed?

That’s GPS speed. I upgraded to a GPS speedometer

Then something is wrong because that is negative 15 percent slip. Pick a number... prop pitch, drive ratio, rpm, or mph. One or more of those is not right

Yea I dunno, guess I’ll just have to take it somewhere. Something isn’t right

If you’re indeed going 35 mph GPS, your tach is off about 1000 rpm’s ( using 15% slip) 42-4600 rpm is the full throttle rpm range what the mercss run, these are basics the same engine….. it’s probably running about what it should

Heres a test on a 2004 Stingray 185lx with a 3.0l also
https://www.boats.com/reviews/perfor...ingray-185-lx/

Ayuh,..... Cross-check the tach against a known good shop tach,....
I'm guessin' the boat's tach is off,....