Volvo Penta prop help

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BRICH1260

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Can someone help me understand VP props. I currently have a DPS-A with stainless F5 props powered by a 5.7 GXI-J, 320 hp, The max RPM is 5K. I am not getting max RPM, only about 4300. My hole shot is good.

What is the range that I need to move to get the higher RPM`s, do I go down to F4`s or lower or higher to F6+?
 

Scott Danforth

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you go down to F4's to bring your RPM's up about 400 RPMs as the numbers go higher, teh pitch goes higher.
 

BRICH1260

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you go down to F4's to bring your RPM's up about 400 RPMs as the numbers go higher, teh pitch goes higher.

Thanks that's what I needed to know.

Just thinking out loud, out of curiosity, has anyone ever ran two different props, say an F5 with an F4. Is this detrimental to do so, any harm done?
 

Scott Danforth

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I have accidentally done that because I lost a prop hub. was with B series, rand a B6 forward and a B5 rear for a week.
 

CuddyLicious

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I have accidentally done that because I lost a prop hub. was with B series, rand a B6 forward and a B5 rear for a week.
And what was the result? I'm considering this. I'm stuck between F6 and F7 sets. I have a 24' Monterey 248 cuddy with VP 8.1L 4200-4600 WOT. The F6's give me 4800rpm's and the F7 give me 4400. The boat struggled to get to 4400 with the F7's and was sluggish out of the hole while it's peppy out of the hole and thru the entire RPM range with the F6's. I've thought about putting a F7 rear (smaller) on to split the difference but am reluctant to do so as VP warns against this. Also considering adding pitch to the F6 set to drop 200 rpm's and chase those 2-4 mph at top end. Thoughts?
Thanks
 

Scott Danforth

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And what was the result? I'm considering this. I'm stuck between F6 and F7 sets. I have a 24' Monterey 248 cuddy with VP 8.1L 4200-4600 WOT. The F6's give me 4800rpm's and the F7 give me 4400. The boat struggled to get to 4400 with the F7's and was sluggish out of the hole while it's peppy out of the hole and thru the entire RPM range with the F6's. I've thought about putting a F7 rear (smaller) on to split the difference but am reluctant to do so as VP warns against this. Also considering adding pitch to the F6 set to drop 200 rpm's and chase those 2-4 mph at top end. Thoughts?
Thanks
run the F6's. that 8.1 will spin 4800 RPM all day long
 

CuddyLicious

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That’s most likely what I’ll do. Have you any experience with mixing duo prop sets with success? What harm could it cause to the drive long term? Thanks.
 

QBhoy

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Hi. If these are the original props for the boat...I’d be totally amazed if the props are the issue. This would be the first time I’ve heard of a Volvo Penta DP set up to be propped anything other than perfectly almost.
you sure it’s nothing else going on ? You want to be between 4600-5000 rpm. Honestly. I’d be amazed if that’s your issue. I’d check out things like the Diz cap, trim...hull growth. Trim tabs aren’t left down at top speed etc. Etc.
 

CuddyLicious

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These are not the original props< When I bought the boat it had F5's and was way under propped for my liking. The F6's are almost perfect but puts me 200 RPM's over WOT. (4200-4600) Id prefer full throttle to take me right to the top of suggested WOT. The F7's put me in the middle of suggested WOT but i didn't like how the boat performed. I was just asking if anybody has had any luck in mixing sets, make like a F6.5 if you will. Ill probably have them worked a little to add pitch to reduce RPM's by 200 and gain a little top end.
There's nothing wrong with the boat, It's me who has the problem.😊
 

QBhoy

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These are not the original props< When I bought the boat it had F5's and was way under propped for my liking. The F6's are almost perfect but puts me 200 RPM's over WOT. (4200-4600) Id prefer full throttle to take me right to the top of suggested WOT. The F7's put me in the middle of suggested WOT but i didn't like how the boat performed. I was just asking if anybody has had any luck in mixing sets, make like a F6.5 if you will. Ill probably have them worked a little to add pitch to reduce RPM's by 200 and gain a little top end.
There's nothing wrong with the boat, It's me who has the problem.😊
Ah. I was perhaps referring more to the gxi 5.7 original post. But great to hear all related details. I take it you have a big block, with those lower rpm ? Just read it’s an 8.1 you have. I’d think your rpm limiter would come in around just short of 4800 anyway. Wouldn’t worry about the integrity of the drive. Those drives are Hardy things and will have likely the highest ratio available with your engine.
 

jbcurt00

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And what was the result? I'm considering this. I'm stuck between F6 and F7 sets. I have a 24' Monterey 248 cuddy with VP 8.1L 4200-4600 WOT. The F6's give me 4800rpm's and the F7 give me 4400. The boat struggled to get to 4400 with the F7's and was sluggish out of the hole while it's peppy out of the hole and thru the entire RPM range with the F6's. I've thought about putting a F7 rear (smaller) on to split the difference but am reluctant to do so as VP warns against this. Also considering adding pitch to the F6 set to drop 200 rpm's and chase those 2-4 mph at top end. Thoughts?
Thanks
Start a topic about your VP & prop selection, asking here in Birch's topic is considered a hijack, and should be avoided.

Also to be avoided is posting to topics w no new posts from the topic originator in 90days or longer.

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