| Author |
Message |
    
Denis-Martin
Member
Username: glastron24css92
Post Number: 7
Registered: 04-2009
| | Posted on Sunday, June 28, 2009 - 04:32 pm: | 
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I got a 290 DP, is it possible to hook only a single volvo penta prop on that outdrive(replacing the bigger one) to get more speed, i have the C7 setup on it right now and it's too small, i might have more choice in a single prop setup. is it the same shaft size?? any ideas would be appreciate. |
Ricardo E.
Advanced Member
Username: ricardomarine_vp
Post Number: 348
Registered: 03-2009
| | Posted on Sunday, June 28, 2009 - 06:37 pm: |
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Short answer, NO!
You do not mention which engine this is!!!!
I gather from your comment that WOT can be easily achieved! So easily, that you want more speed and cannot get it from C-7's!
Is the over-all gear ratio correct for your engine?
If you have the 1.95:1 now (for example), you may want to try switching to the 1.78:1 and then try different prop sets.
(make sure that the C-7's are in perfect tune and are a matched set before giving up on them)
Use the WOT RPM test just as you would with a single prop drive. |
Denis-Martin
Member
Username: glastron24css92
Post Number: 8
Registered: 04-2009
| | Posted on Wednesday, July 22, 2009 - 09:17 pm: |
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The engine is a custom built 496 stroker, 560 hp @ 5700 RPM and the peak torque is 605 @ 3700 RPM. Right now i'm running 63 mph at 5250 RPM. At that exact RPM, (looking at the dyno sheet) i'm at 553HP and 553 of torque! I checked my outdrive ratio today and it's a 1.78:1, is there anything lower than 1.78:1???, My buddy had the same boat as i have right now, with almost the same HP with a mercruiser setup getting 80 mph with a single prop and at a lower rpm too. Any advise???? |
Ricardo E.
Advanced Member
Username: ricardomarine_vp
Post Number: 437
Registered: 03-2009
| | Posted on Wednesday, July 22, 2009 - 09:44 pm: |
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Any advise????
Yes, you need to consult Volvo Penta Technical Division and ask this question. You may benenfit from a high performance Single Prop drive and special propeller. |
Morten Ringvold
Senior Member
Username: haffiman37
Post Number: 3975
Registered: 04-2006
| | Posted on Wednesday, July 22, 2009 - 09:48 pm: |
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Max speed and duo-props have never been a good combination, at least not if You want past 50 knots.
Unfortunately the rpm (speed) range that the duo props works withing is rather limited compared to single props. As soon as You get out of the rpm range, the props just starts working against each other and consuming the power You need for increased speed. In Your case I would have opted for a single prop solution, but there again Volvo is not the fastest drive compared to the Mercruiser. You will never catch up Your buddies! |
Ricardo E.
Advanced Member
Username: ricardomarine_vp
Post Number: 438
Registered: 03-2009
| | Posted on Wednesday, July 22, 2009 - 10:44 pm: |
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Agreed, this drive was never intended for this usage! |
Robert A. Fierro
Advanced Member
Username: sandkicker
Post Number: 736
Registered: 06-2008
| | Posted on Thursday, July 23, 2009 - 12:39 pm: |
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Volvo drives have a lot of advantages over Mercs.. Unfortunately, lower drag isn't one of them. When all is said and done and you get the best you can from the Volvo parts bin, your buddy will always have a couple of knots advantage over you. |
