High rpms

[brew42]

I have a 4.3, in a 185 glastron, that runs 41mph at w.o.t. with 6000 rpms (book has 4200 - 4600).The prop is 14.25 x 23. Tried a new prop (same pitch) ,thinking the hub was slipping, same result. Owned the boat for one month. Pulls tubes and skiiers well. Not sure if tach is wrong but mph seems low. Any ideas?

 

[bruceb58]

Get a shop tach and test it.

Also, the little selector switch on the back of your tach might be set to the wrong number of cylinders. Check that first.

 

[brew42]

The tach setting is correct, I will get a shop tach. Thanks

 

[skydiveD30571]

6000rpm is really high for a 23" prop and 4.3. I'd guess an incorrect tach reading on the gauge too.

 

[Scott Danforth]

not to mention at sustained 6000 RPM, the pistons like to swap bores on a stock V6.

I am going to go with a bad tach or the switch is set to 4 cylinder

using a prop calculator, 23 pitch, 1.84:1 drive (guessed) and 12% slip gives you 4000 RPM at 41mph.

 

[brew42]

Checked the rpms with an automotive meter that reads rpms, tach said 1000 at idle. Actual rpms were 620 rpm. At 4000 tach reading actual was 2730. Did not have a small screw driver in the boat (while on the water) to calibrate tach. Thanks for the info.