Selecting props for volvo penta DP

[vball]

Just swapped SX to DP - engine is volvo 5.0 GXi - DP drive ratio is 1.78 - altitude greater than 5000', boat length 21'. Is there a matrix that can assist with starting point; i.e., F5, F3, etc?

 

[Leardriver]

Re: Selecting props for volvo penta DP

Volvo is very secretive about actual pitch for the Duoprop.

Someone on here did an analysis that seemed to indicate about 1.5 inches of pitch per different series, like F5 to F4. If your boat has an F5 on it for sea level, you need an F2 for watersports in Denver, or an F3 for better fuel economy cruising at Lake Powell.

What is your current RPM and Duoprop series?

By the way. I know of someone who could use a 15 pitch SX prop in Denver, if you still have some SX props left.

 

[vball]

Re: Selecting props for volvo penta DP

I do have two SX props available - both alum. One is a 19 pitch 3 blade, other is 20 pitch 4 blade.

I just purchased the drive unit, without the priveledge of props...starting from scratch and looking for advice. F2 through F5? Oh, where to start?

 

[Leardriver]

Re: Selecting props for volvo penta DP

F2 absolutely if you are going to be in Denver area lakes.

 

[vball]

Re: Selecting props for volvo penta DP

Ok. and that's considering the 1:78 drive ratio

 

[Leardriver]

Re: Selecting props for volvo penta DP

Yes. I thought that many of the DP drives a standard load in most cases. F3 is more pitch, and if you were always at Lake Powell or even Pueblo, and just want to cruise or pull a tube, it would be better.

The props are crazy expensive. I saw a used set on the Skagit, Alaska Craigslist a week ago for $500.

 

[Leardriver]

Re: Selecting props for volvo penta DP

A set of F2's just listed on ebay in Florida under Volvo Duo Prop in the boat acc section.

 

[vball]

Re: Selecting props for volvo penta DP

Lear - I picked up a set of F3's from a local shop. Boat runs at 4300 (max 5000) and 40 mph. If I pick up F2's, am I going to lose top speed while raising the RPM?

 

[Daleg70]

Re: Selecting props for volvo penta DP

not knowing the boat or engine --- if you look at the a VOLVO prop guide --- for a DP drive with 1.78 gears (either 5.0 or 5.7 engine)
it shows the F3 props as about 41 MPH at 4600 and 44 at 5000, it show an F2 at about 37 at 4600 and 41 at 5000.
My guess is that you might gain slightly by getting the RPM up to the proper range, probably will not loose top end, and should gain acceleration. At your altitude I would think the F2 makes sense.

PM me if you cannot find a VOLVO PROP GUIDE online ----

I also assume you are using a GPS for the speed --- not any other speed indicator.

 

[Leardriver]

Re: Selecting props for volvo penta DP

Since you are so far below the peak RPM, with an F2 set you will turn closer to 4700 and probably as fast or a knot faster because you will make some more HP by turning the engine over faster, like daleg said.

You don't really have a choice. If you keep the current props, you'll hate the performance because it will be such a slug out of the hole.

High altitude kills us! We go from 21 pitch and 50 mph at sea level with a lot of boats and 15 pitch and 40 mph up high.