Potential Prop or Gearing Problem

[checkyourmirrors]

I have a 2005 Chaparral 240 Signature and recently had some exhaust valve damage and had all new valves and machined heads installed. We are still searching for the root cause which the service center felt was overloading. The boat does blog down when trying to plane and according to the service center optimum plane is at 4100 rpm. The Volvo shop suggested I take it to a Chap dealer for further diagnostics.

My 5.0 270hp Volvo MPI engine should operate at 4800 WOT with the F4 Duoprop. After all this work my WOT is 5200 rpm and all seem to agree I need to switch to an F3 prop for faster planing and lower cruise rpm. However I am concerned the reduction in pitch is going to push my WOT to 5,450 rpm and if the over rev limiter kicks in, aren't I basically losing power.

Any advice or guidance on what/where I should be looking at would be greatly appreciated. Gearing ratio has come up, changing the prop, etc and the engine seems to be running perfect so it hasn't been suspect.

 

[steelespike]

Re: Potential Prop or Gearing Problem

I'm a little outside of the prop experts.
I've aften wondered about the Volvo Mystery prop numbers.Do you know the pitch involved?What is the pitch on the F4?F3?
Usually a sluggish hole shot doesn't go with excessive rpm.
Can you get us the present max speed,rpm,with a light load.actual prop pitch,Gear ratio,
Boat weight and or type.Your estimate of how long to plane?
If the motor was operating within its rpm range I don't see how sluggish planing would affect engine health unless it had an existing problem.

causing generally sluggish perfortmance.