Reply With QuoteA five blade, like a High Five by Mercury, may do the trick for you. It will suffer just a tad in the top end but it will rev a little higher. They work great.
Motor is stock, only having thru-hull exhaust.
I'm turning a 21P 4-blade "Revolution" prop.
Boat runs 60mph with two people and low fuel.
I also only get about 4600rpm out of her.
Is this the correct prop for this boat?
Seems to me that I should be about to get closer to 4800rpm on this motor.
If I had my way, I'd rip out this motor and put something bad-ass in, just don't have the jack and have to work with what I got.
Any advice?
A five blade, like a High Five by Mercury, may do the trick for you. It will suffer just a tad in the top end but it will rev a little higher. They work great.
Don't bother wasting money on a motor for a cheetah. I put a 540 in mine only to see 70 mph so far. Oh well...there goes 20k.
Not sure why the 540 won't push it faster. Doghouse had a 572 in his 23 and it was in the 90's. Mine only has a 528 and it's in the teens (Doghouse teases me about my "little" engine). Not sure but Bob may be mounting the drives lower in the 24's. The bottoms are the same as the 23's with the addition of the molded swim step. I've got a short drive in the #4 speedmaster. The prop CL is 2" below the center pod but Doghouse's was a stock length bravo.
I have about 2 hours on it. So far I've run a labed 28-4 blade @5000 @ 68mph and a 26 bravo @ 5000 @ 70mph. The prop ventilates while planing so I don't think my drive is too low. Peak tq is 735 @ 5000 and peak hp is 793 @ 6000. When I bought the boat used, I was told by cheetah that it ran 114 with 900 hp. The previous owner kept his motor and built a new 24.
MOBrien
I had the 7.4 and ran a 23/3 @ 62 on gps w/ me and 5 gallons in 55 degree dry air and perfect wind chop hitting the rev limiter which according to my manual is 4680 rpm. The acceleration w/ a 3 blade is pathetic. I usually ran a 22 bravo 4 blade fully loaded at 56 mph and 4600 rpm in hot weather. Hope this helps.
I 've read somewhere on here about someone who procharged a 7.4 mpi and claimed 81 in a stilletto. I curious if the motor lasted and how much boost they ran.
Cheetin Brad, Sounds to me like you should be running that thing closer to 6000 rpm to get it at its peak horsepower instead of peak torque. My 509 makes the most horse power at 5700 rpm and that is where I run it, my prop guy tried to have me run it at peak torque and that was a mistake. 22 Advantage Citation, prop 23 rev4 78 mph on gps at 6200 ft.
Clint
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