Little Formula prop help.
11-01-2012, 05:19 PM
#1
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Little Formula prop help.
http://www.facebook.com/photo.php?fb...type=1&theaterI wanted to get a 22-25ft boat, but since getting my business running is top priority, picked up a 1979 Formula F18 in very nice shape (so I thought) for $3500. It ran good but at 38-40 mph it got very unstable with porpoising. Turned out to be a bad transom. I have repaired the transom. Along the way I upgraded from a log manifold to higher performance GLM center rise exhaust. I have it all back together and it runs very well. Never gets unstable unless I over trim. It likes to have little to no trim. Anyways, with my old 21p aluminum prop I was getting 50-51 mph at 5500 rpm when I backed off. So I then threw on a 23p aluminum that was with the boat. I got 53-54mph at 5000rpm. I know my current props are old and crappy but where should I go from here?
11-01-2012, 10:57 PM
#2
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Welcome and....you are on the right track.
Back in the day I had the same boat with a 302 Ford V8 and stock with a 19" Stainless it would run 49 with a 2 barell carb. With a 271 horse Shelby Mustang cam, Edelbrock Performer intake, 600 Holley Double Pumper and some head work it would run 65 with a 25" Cleaver at 6000 RPM.
You don't say what engine you have but if you are turning 5500 RPM you are making good power. We have much better props these days and I think with a properly tuned 23" Bravo I 4 blade you should approach 60 potentially. Don't even think about an old cleaver...they were terrible getting on a plane.
Give some more details...I'm sure others will chime in on this one.
Back in the day I had the same boat with a 302 Ford V8 and stock with a 19" Stainless it would run 49 with a 2 barell carb. With a 271 horse Shelby Mustang cam, Edelbrock Performer intake, 600 Holley Double Pumper and some head work it would run 65 with a 25" Cleaver at 6000 RPM.
You don't say what engine you have but if you are turning 5500 RPM you are making good power. We have much better props these days and I think with a properly tuned 23" Bravo I 4 blade you should approach 60 potentially. Don't even think about an old cleaver...they were terrible getting on a plane.
Give some more details...I'm sure others will chime in on this one.
11-02-2012, 04:37 PM
#3
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I am running a Mercruiser alpha one 260Hp with an edelbrock carb and GLM hi flow center rise exhaust. I was thinking a 23 mirage plus, or maybe even a stiletto, or maybe a 25p and lab it to get RPMs back if I have to. I was hoping to prop it for $350-400 though.
Last edited by 79formula; 11-02-2012 at 04:39 PM.
11-03-2012, 09:39 AM
#4
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He will be my go to guy when I start focusing mine in.
You need 300 HP to break 60 in that boat....which is easily obtainable. You put a set of Vortec heads and a roller cam with an Edelbrock Vortec intake you'll be making 375+ and will have no problem spinning a 25"....potentially a 70 MPH rig.
11-03-2012, 10:05 AM
#5
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I am thinking of just dialing in my current setup and calling it a day. I would rather have fun with it for now as I hope to step up to a 25 or 27 in the future.
