Need a new prop, but which one?

[Burtonair01]

Hello to all you experts! I have a prop question. I have a 2001 Doral 250 SE with a 5.7L GXI Volvo Penta 320 HP duo Prop. I just bought the boat from a guy who kept it at a lake that was 7200' elevation, he was running the F3's. I will be doing most of my boating at an elevation of 4500' on one lake and an elevation of 3500' on another lake. So my question is,which prop should I buy for the lakes I will be boating on? I ran the F3's all weekend and was running 38 MPH @ 5200 rpm @ WOT on the 4500' elevation lake. I know this is high rpm's, at least I think it's high.

 

[usskydvr]

Re: Need a new prop, but which one?

You are right at the MAX RPM for your engine 5200. You should be good to go. ( Generally you lose about 3% of HP for every 1000 ft of altitude gain) I doubt he was able to turn 5200 at 7500ft. I wouldn't change the props.

 

[Burtonair01]

Re: Need a new prop, but which one?

Thanks, that's what I was hoping for cause those props aren't cheap! I was at the lake a couple of day's ago and was running 40MPH at WOT and was only running 4800 RPM's so I think you are right on staying with what I have on the boat. I had a 3/4 tank of gas and half full of water and loaded for bear. Motor is running hot now, so I have to figure that one out. New impeller also. Ideas?