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'89 formula 272 sr-1 only 55mph with twin454 ?
I have a '89 formula 272 sr-1 with stock 454 merc 330s and Bravo1 drives... spinning 4 blade 24p bravo props
Gps is 55mph at 4400rpm. seems a bit slow to me for that set up. anyone have ideas or different prop setup for this rig ? any and all input is welcome. This boat is new to me this season. My other boat is a 78 Donzi 21GT with single 330 trs spinning 23inch 3blade cleaver... hits 68 on gps at 4900rpms. Fun, reliable and solid...she's a champ. the new boat is great size wise, but thought it would be 10-12mph faster... again thanks in advance for any ideas. |
That formula is pretty heavy. I've heard of those models getting into the low 60's stock. Sounds like you could use more prop pitch imo. 24 seems a little low.
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Something is off. I have a 311 with 23 pitch mirage. Mine runs 63mph and 4600 rpms with 454s. Would have thought that boat would have had 23 on it, but maybe it had something higher. Maybe your Speedo is off. Was that GPS? |
Originally Posted by MyIsland
(Post 4689491)
Something is off. I have a 311 with 23 pitch mirage. Mine runs 63mph and 4600 rpms with 454s. Would have thought that boat would have had 23 on it, but maybe it had something higher. Maybe your Speedo is off. Was that GPS? The hull is different to me than the Donzi so I'm still shaking her out regarding trim, kplanes, and rpms, fuel load etc. but 55 still seemed sluggish. With the 3 blade cleaver the Donzi runs a 19" pitch for skiing and tubing....up and out of the hole....and a 23 for top end but slower hole shots. how will dropping the pitch or switching to a mirage make a difference? I thought I'd get more top end with the larger pitch prop...these are the props it came with from the previous owner. thanks for the reply |
That's about all she wrote with the magnums maybe mid to high 60 mph range my 02?
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I had a Formula 292 SR-1 that originally came with 330's. I tested, Mirage, Bravo, Hydromotive QIV and Rev 4 props. My favorite was the hydromotive Q4. I was able to get 63 mph out of that combo. A 272 should see 64-65 with 330's. My guess is your engines are tired and or your carbs need a good cleaning.
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What pitch was those props? Did you loose any top end with the 4 blade? What did it do for you vs the mirage? How many hours on the boat..... back the 272? |
Sorry should have posted that. Mirage was a 23. Bravo and Hydro were 24's and the Rev 4 was 25.
Also your props could need a tune up, as the prop ages it can flatten out. Also if its been worked on a lot, the diameter could be cut down. Either way, something is wrong. Your boat should be a solid 64-65 mph performer! |
That's what I expected ..64-65... so the investigation begins.... here's to hoping I hit the lottery ;) thanks for the replies! |
I had the same boat and with fresh 350 fuel injected Mags/ 300 HP ran 60 MPH exactly with 21 Mirages at 4500 RPMs. I would check compression of engines first. You are way off the mark so props are not likely the biggest issue here. But that said you may find a better prop combo as well but I wouldn't start switching props yet. You're in the middle of the recommended RPM band so not a terrible set up
. Something else must be a problem. |
Pat, how did you like the small blocks in that boat? Were they reliable?... lots of torque to push that beast, no?
thanks |
My 89 272 with 330s ran 64 with 25 mirages at about 4500rpm
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Originally Posted by lokipk
(Post 4689424)
I have a '89 formula 272 sr-1 with stock 454 merc 330s and Bravo1 drives... spinning 4 blade 24p bravo props
Gps is 55mph at 4400rpm. seems a bit slow to me for that set up. anyone have ideas or different prop setup for this rig ? any and all input is welcome. This boat is new to me this season. My other boat is a 78 Donzi 21GT with single 330 trs spinning 23inch 3blade cleaver... hits 68 on gps at 4900rpms. Fun, reliable and solid...she's a champ. the new boat is great size wise, but thought it would be 10-12mph faster... again thanks in advance for any ideas. |
an inexpensive test could be to put the cleaver from the GT on the left drive and keep the 4 blade on the right to check rpm and speed, If rpm on the left is good and speed increases then proceed with a Mirage 23 on right, then match port to it. if rpm is too high on the cleaver side then go mirage plus, in a set, there is about 100-200 rpm drop from standard mirage to plus. mirage non plus is close to the cleaver in rpm. good luck, Chris bravo 4 blade= ok all around , best cruise Mirage non plus thinner blades = best top end mirage plus, good top end and better planing and cruise than non plus all based on std drive heights. as you go up everything changes. oh , also, if props do not help some then sometimes the baffles in the silent thunder can come loose or fail and reduce the power output by restricting exhaust flow. |
I might try to check the silent thunder before changing props with a light and mirror before messing with props etc. |
Thanks for the prop tips! can anyone explain the difference in hull attitude in reference to twin prop rotation? Meaning spinning in/ towards each other vs. spinning out/ away from centerline? pk |
Following
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My 1991 272 SR1, has a factory made hook in the hull which limits speed.
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be sure to post your results! I have an 89 272 with 25p Mirage (non plus) and 330/bravo's, tops I've ever gotten is 60 mph. (I rarely get flat enough water for speed runs) I think my carbs need tuned up. plugs showed me running rich. motors got 650hrs.
I feel you on the porpoising. I have to run at least 45mph before I can get the drives or planes neutral, WOT is the the only, and I mean the only, way I can trim up both drives and planes. |
Type error. My props were 23 pitch.
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As I remember the 23 Mirages were great for acceleration but the boat hit the max speed very quickly at 61 MPH. Also it was not at the high end of the RPM band so I decided not to increase pitch of props. Maybe 4500 RMS.
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