New prop 6000rpm

[Luk3]

I just put a new Solas Rubex 4 12.75x17 prop on my boat. 90hp Force, 17' Maxus Bowrider. Great power out of the hole, nice low speed plane for cruising, but at WOT I'm getting 5900-6000 rpm. The engine is rated at 5000-5250 I believe. Would it be recommended I go with a 21 pitch?

 

[steelespike]

We need your wot rpm and gps speed so we can evaluate your tach and your setup.
My guess is that a 90 Force on a 17ft bow rider wouldn't over rev.Perhap[s you can borrow a shop tach to check it against.
If we guess your gear ratio at 2.00 slip at 13% a 17" prop at 6000 makes about 42 mph I would say not possible for a 90 Force on a 17 ft bow rider.

 

[Sea Rider]

Welcome to Iboats,

Was the trial done with you alone and lightly loaded boat ? If so and assuming tach is working accurately you have some choices :

-If stated min-max wot rpm for that engine are correct going for a 21 pitch prop should put you arround 5200 rpm
-If achieving 6000 rpm at wot as soon you add more boaters or load rpm will drop accordingly
-No issue if achieving 6000 rpm at wot as long you permanently monitor you tach as not to pass 5250 revs if lightly loaded.
-For peace of mind, install a second cheap induction tach and check if the main reads accurately

Happy Boating