Volvo Penta duo prop what props do i need?

3

38special

Petty Officer 2nd Class
Joined
Mar 9, 2010
Messages
129
How do i choose props for this out drive? I bought it on craigslist with out props. It came off of a 22' stingray with a 350. I'm putting it on a 20' Glastron gs205. I am building a 383 stroker and hp will be 400 or a little above.I'm pretty sure my engine will be in the 5,500 rpm range topped out. I think the guy i bought it from said he had F5's on it. Would F5's be in the ball park with my 383?
 
M

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Re: Volvo Penta duo prop what props do i need?

The F7's came on boats up to 22 feet in general, I know we are not sure why the other boat had F5's, but it is larger with the same size engine as yours. Using that as a baseline for estimating an F7 set should work well on your 20 footer with the HP bump you are giving it. If you boat at 3500+ feet then I would go down 1 in number for each additional 1,000 feet, all estimates on that.

My recommendation assumes you are not building a totally high-end horsepower engine. If you are sacrificing low end torque to gain more HP at higher RPM powerband then all bets are off, you may need F5 or even F4 to get out of the hole and into the higher power band.

F5 versus F7, the F5 will give better acceleration from a dead stop than F7 but not as much top speed. This is assuming the engine in the boat can turn the F7 set to the same top rpm. If it can then the F5 set may have an over-rev potential and you would have to watch the tach and throttle down accordingly.

I have attached a Volvo Pent prop guide, you can look up the F series and a similar engine to compare the differences.

Watch that 5,500 rpm top end, that will be pushing what the drive can handle.
 

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3

38special

Petty Officer 2nd Class
Joined
Mar 9, 2010
Messages
129
Re: Volvo Penta duo prop what props do i need?

Thanks, that is helpful information. The engine is being built more for torque. Heads are 180cc raised runner iron heads with fast burn combustion chambers. The cam grinder told me with those heads that the engine will start dropping off at 5,000 to 5,500 but will have real good tq just off idle through 5,500 rpm. Comparing other builds it's likely an easy 400 to 450 hp with tq numbers close to those.
 
M

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Re: Volvo Penta duo prop what props do i need?

Sounds good, I think the F7's will be the ones for you.
 
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