Right prop or bad tach.

[Jersey Bill]

Have a 21 ft glass cuddy w/a 90 Johnson 150 kicker. Boat weighs 3300 dry. Has a 15X17 alum. for blades. Problem is when at WOT I'm doing about 36 mph, but tach is at 4800 rpm's. Would like to get motor into operating range of about 5500 which is in the ballpark. Am I overpropped? or maybe underpowered for that boat. Coast guard approved for a 175. Also having a problem with getting up on plain. Take about 15-20 seconds. Any ideas?<br /><br /> Jersey Bill

 

[sharkcat]

Re: Right prop or bad tach.

Decarbon the motor give it a tune up etc check compressions then try it again if the WOT rpm is still low get the tach checked if ok try a lower pitched prop for every inch in pitch you drop you will gain about 200rpm.How your motor is set up on the boat can affect rpm as well the cav plate should be level or slightly above the bottom of the hull.Hope this helps

 

[Fouled Plug]

Re: Right prop or bad tach.

Good suggestions from Sharkcat. When you find the correct prop for your application, consider a hydrofoil (Stingray, Doel Fin, etc) to help your planing and cruise. properly set up, a foil works wonders on heavy boats. Good luck!

 

[roscoe]

Re: Right prop or bad tach.

Ditto all above. But also underpowered.