bajacountry

Hi Guys,
Ditched my 330's for 502 MPI's. Before they went in had valves done on both to be on the safe side.
With the old motors, I was turning 22P Bravo 1 four blades going 58 at 4400 RPM's on GPS. I now have on 24P Bravo 1's four blades turning 4800. My GPS isn't working now so I don't know exactly how fast I'm going (speedo says 64). The tachs are original so they're not the greatest. Any of you guys running the same power set up? If so, what prop is best, and what should RPM's be? I'm looking for 70!

Formula311-SR1

You should be real close to 70 with that setup. In our 89 311 we upgraded from modified 330 motors to 502 MPI that we swapped out the MPI system for dart intakes and carbs from an HP 500. With labbed 24 Hydromotives we would see between 70 and 71 @ about 5200 RPMs (on GPS). Drives are turning out.

Hopefully someone running bravo props will chime in. Not sure if they are turning drives out or in? When I tested 24 bravos I had low rpms and slower speeds turning drives out, and turning in was similar to the hydros.

Sharpened stock hydromotives seem to work the best for me so far.

endeavour32

iTrader: (4)

I've got a 89 292 but the speed between it and a 311 is almost the same. I've got a pair of 425 454's in my boat so it should be very comparable to your engines. With stock 25 pitch Hydro's I get 68-69 MPH @ 5000 rpms. With Labbed 25 Bravo's (24 castings)- 68 MPH is my best @ 5200 rpms. The Bravos were labbed at Mercury and I've been talking with Brett at BBlades and he says the labbing recipe is wrong so there is more potential there.

If you have a smartphone, down load a GPS speedometer app. There are plenty that are free. The one that I have found to be the most accurate is SportsTracker. One thing to remember is if it's 90 degrees and humid your speed will suffer. Last week when I was hot (90 and humid) 64 is all I could get out of my boat, yesterday it was 70 and I was back to 68-69. Good luck and let us know what you find out.

bajacountry

Thanks for the feedback. Haven't had a chance to get out. Will reset GPS and see what it's really at this weekend. Someone here said they were turning 26 B1's with same power. sounds a bit much, but a buddy has a set so I will try them too. Formula, are you saying that you were hitting 70 with the 24 Bravos turning in?

88242LS

Got twins runs 62 with 330's so i would think 502's should push u to upper 60's, when ya coming to buffalo?poker run in three weeks

Formula311-SR1

Best I saw was 68.8 with 24 bravos turning in, but under 35 mph I had a horrible cavitation for some reason. Really sucked for our night time speed limit.
That's why I was hoping someone else running bravos would chime in. See if they had similar results?
For reference, with upgraded cams from marine kenetics and bigger carbs, we turn 5300 with stock 26 Hydromotives. I don't think I can swing 26 bravos.

Rattlesnake Jake

iTrader: (2)

I don't think you'll be able to turn the 26 B1s.

Chris

i had a 91 311 with 502's - bravo boat with drives turned out (tried it in as well) the boat would run 71-72 gps. 24 pitch prop.

endeavour32

iTrader: (4)

Chris- were you running Bravo props?

Chris

yes i was