6k+ RPMs - normal?

[1badhusky]

Hi, just got a 2007 bayliner w/ the 4.3 mpi. The engine seems to run great - maybe too great - the tach goes to 6k, but at full throttle the rpms go beyond this into the great unknown area beyond 6k...any idea why this would be?

Top speed is 55mph - about what it is supposed to be, and not hitting any rev limiter that I can sense.

Is this just a tach that's not correctly adjusted? Is this engine supposed to rev that high? Boat didn't come w/ a manual, so i'm still waiting for one to arrive.

Thanks!

 

[spectrum]

Re: 6k+ RPMs - normal?

no its not supposed to be that high. what is your prop size. a have 06 bayliner with the 4.3 mpi and i have yet to tach out. my prop pitch is 19

 

[achris]

Re: 6k+ RPMs - normal?

The MPIs rev limit at 5100... If your tacho is showing passed 6000, then I think you have a faulty tacho....

 

[haulnazz15]

Re: 6k+ RPMs - normal?

Also, a good hint, does it sound like 5K or does it sound like 6.5K rpms? You will definitely know if you're truly running 6.5K rpm because that thing will be screaming. Faulty tach for my guess. I would've guessed your boat topped out at less than 50 though, did you measure with GPS or the dash speedometer?

 

[Philster]

Re: 6k+ RPMs - normal?

Top Speed checks on GPS need to be done in two directions. Average the two.

Head down current and you could inflate your speed greatly. My buddy swears his boat does 70, but he still doesn't understand why it's only down river.

 

[picklenjim]

Re: 6k+ RPMs - normal?

Your tach is definitely incorrect.Some tachs have a small screw on the back to calibrate them. Also there is a dial on the back to set for the number of cylinders your engine has which may be set wrong.

 

[PiratePast40]

Re: 6k+ RPMs - normal?

Photo Tachometer - $39.99 at Harbor Freight

 

[1badhusky]

Re: 6k+ RPMs - normal?

Yeah, I really don't think it is turning 7k rpms...not sure on prop size - will have to look.

Actually, the boat is supposed to do 57-59 mph in the tests I read...it's light - 2200lbs, with decent engine 220hp.

Figured mine will be a bit slower w/ the weight of the tower and extended swim platform, plus the prop is just a bit dinged up. I did the gps thing both up and down stream, fastest reading was 54.5mph.

Thanks for the heads up about the calibrating thing on the back of the tach, I'll have to check that out, cuz it's way off - or I'm way off and gonna fry my engine.