Jamesbajaboss

If you going over 5000rpm your blowing your engine DO NOT GO OVER 5000
SPECS ARE 4600 -5000 WOT
The previous owner lie to you

Jamesbajaboss

25p prop you're over prop for sure

mcollinstn

A 454 Mag won't blow up at 5500 rpm.
It just won't benefit you any to spin it that fast. The horsepower peak is around 4800, beyond 5000, you are losing hp.
A camshaft change to something with more duration will shift your power curve to a higher rpm if that's what you want.

cableguy1979

Yeah i was planning on propping for 4800 to 5000. I have turned the boat 5000 a few time and been 60 on gps but I was not running a big enough diameter prop and it was slipping something horribly. This engine I have in it now is 502 mag mpi gen vi. Its .030 with slightly higher compression but not enough to matter. I tried to do a camshaft change but everyone kept telling me it cant be done without the factory exhaust and silent choice being changed. I simply want to cruise at 40 mph 3200 RPM tops. Once in a blue moon I will push it to top speed but at the price of props I dont want to spend $500-$700 on a prop that is less than optimum.

cableguy1979

I have the 415 hp 502 mag mpi gen vi with a bravo one 1.5 ratio drive.

Jamesbajaboss

Ok
sorry for the miss information I thought you had a 454 MPI 385 hp I gave you the heads up because that's what I have and I went thru the same thing, same size boat w/454 MPI Mag 1997 Baja Boss 25.2
then you should do well with the 24p 4blade(Bravo1) if not the rev4 21p but you are any where in between a 4 blade and a 3 blade ,the 25p I still think your are over pitched, with the four blade you'll loose 1 or 2 miles per hour but a lot more stability, hole shot etc.
I wish luck !!
Thanks
James

cableguy1979

I found a great deal on a brand new in the box Rev 4 21p for $100 so I think Im going to buy it. Fix the Bravo 1 24p and try it. I have a buddy that will let me borrow a tempest plus 3 blade 21p x14 5/8 and I also have a Turbo 21p Ill try and or sell to get a Mirage plus. Between the Mirage plus, the Bravo 1 four blade and the Rev 4 I should be able to find a prop that works best for this boat. I will want to try a 23p 3 blade eventually.

Jamesbajaboss

Try the rev4, the tempest 3 blade and the Rev4 are practically the same prop they built the rev4 based of the Tempest plus
Thank you
James

Baja Rooster

iTrader: (1)

The Rev4 is superior to the M+ in every way on my 272 Islander. They work great for getting our heavy cruiser hulls up and out of the water.

bajaman

There are all sorts of "boat speed calculators" out there that take into account prop pitch, outdrive ratio, rpm, slip, etc. At some point it is all a math model. Figuring 10% slip and a 1.50:1 outdrive ratio, here's the speeds @ 5000 rpm according to one of them:

• 21" prop = 59.7
• 22" = 62.5
• 23" = 65.3
• 24"= 68.2
• 25" = 71.0
• 26" = 73.9

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