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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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