lanehill

Hi I just got a 1997 checkmate zt240 with a 454 mag and a 25 pitch prop the problem is it will hardly plane out with 2 people and won't with any more I can only get about 60 on gps at WOT running 5400 rpm I've herd it should do about 70 don't know if this is true or not just wounding what you guys think maybe wrong pitch?
Thanks for your help!

sabo

iTrader: (2)

If those numbers are accurate then thats about 30% slip, when it should be more like 15%. Is the prop damaged? I would try another prop and get baseline numbers.

Gimme Fuel

Those RPM seem quite high. Is it a carb or EFI motor? Efi motors rev limiter was 5150 rpm........Need to know for sure which 454 you have. 7.4 mpi, 454 MAG MPI, just 7.4 carb?

lanehill

Prop is in great condition and its a 7.4 carb I was thinking about going to a 23 pitch but then I wo lose top end speed right?

lanehill

Btw the prop is a mirage plus

sabo

iTrader: (2)

maybe rpm's are 4400 and not 5400? that would make ALOT more sense, slip would be around 13%, as Gimme Fuel said, you should be hitting a limiter around 5,100 and shouldn't be spinning a stock 454 much past 5,000

Going to a 23 pitch would make rpm's raise by 300-400 rpm if mph stayed the same.

H TAYLOR

I had a 99 240 with the 7.4 efi... 22 p bravo 4 blade was best with a top speed of 65.

SB

iTrader: (1)

Yup.

1.5 gear ratio
5400 engine rpm
Theoretical Speed will equal 85mph
Actual Speed 60mph

Equals 29% slip.

but,
if it has
1.65 gear ratio
5400 engine rpm
Theoretical Speed will equal 77mph
Actual Speed 60

Equals 22% Slip, which is more believable but still means your tach and/or prop sucks. Excuse the french.