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22 DAYTONA 08-11-2010 01:23 PM


Originally Posted by zx14 (Post 3180087)
sounds like I have an issue or was lied to. I run a labbed 32 bravo prop on a imco shorty,"gears unknown" with what I was told a 500 efi converted to a 540 cu. in. with a procharger pushing 8lbs with 60 lb injectors, was told the motor was 960 HP. 5800 rpms gets me 98 MPH, 4 people on board with half full of fuel.

That sounds like about 600Hp, or the set up is very wrong. the above boat will do that speed full of people, beer, and fuel in the heat. It just takes it longer to get there.

zx14 08-11-2010 05:39 PM


Originally Posted by 22 DAYTONA (Post 3180161)
That sounds like about 600Hp, or the set up is very wrong. the above boat will do that speed full of people, beer, and fuel in the heat. It just takes it longer to get there.

maybe the speedo is off? the prop is a 32 and pulling it to almost 6000 rpm takes some HP????

I dont know my gear ratio but I can cruz at 38mph at 2700 rpm

DonRoc 08-11-2010 10:06 PM


Originally Posted by zx14 (Post 3180371)
maybe the speedo is off? the prop is a 32 and pulling it to almost 6000 rpm takes some HP????

I dont know my gear ratio but I can cruz at 38mph at 2700 rpm

Your speedo is off, or the prop is slipping a bit much. with 1.5 gears top speed @ 5800 should be around 103, Cruise @ 2700 should be near 48mph. With your setup I would guess 750hp. I worked on a 540 with AFR heads, a M3 9psi that made 840hp on the dyno. And that seems to work with the numbers you should be running at that rpm.

zx14 08-11-2010 10:16 PM

thanks for your input. motor is suppost to be 540 cu in it has a lumpy cam but idels at 900 ok, dart pro 1 heads , M1 procharger, 60 lbs injectors,msd , the mcu was done by arizona speed and marine. I am thinking I may be only doing 5000 rpm, I am going back to the lake saturday

DonRoc 08-11-2010 10:50 PM

5000 is a long way fom 6000 in your last post. Still things dont ad up. And the M1 is running pretty hard to make 750hp.
Take a good GPS with you, and a note pad to with you to write things down, (speed, rpm, drive ratio, prop, conditions, fuel and people on board).
Good luck. I should know if I am getting the 27 this weekend

zx14 08-12-2010 07:10 AM

Thanks Don. there is no marking on the drive for the ratio, is there a ez way to fiquer it out?

good luck with the 27!

I have had 2 - 21' daytonas a 25' daytona and now this 26'. If even at 0nly 100mph This one is the most stable.roomy and rides best. "damn sexy looking too"

skydog 08-13-2010 11:28 AM


Originally Posted by zx14 (Post 3180740)
Thanks Don. there is no marking on the drive for the ratio, is there a ez way to fiquer it out?

"

Yes i too would like to know!!

DonRoc 08-13-2010 12:24 PM

Put it in gear mark the prop shaft, turn the motor over from TDC to TDC one revaluation. See how far the prop shaft turns. 240 degrees is a 1.5 ratio, 267 deg is a 1.35 ratio. If it comes out of gear hard don't force it, Hook up a remote starter and start it in gear then shift to neutral, this is best done on a hose.

zx14 08-13-2010 03:05 PM

ahhhh, so it is 1 revolution of the prop is ether 1.5 or 1.3 revolutions of the engine. I always thought is was the other way around.

DonRoc 08-13-2010 03:17 PM


Originally Posted by zx14 (Post 3182011)
ahhhh, so it is 1 revolution of the prop is ether 1.5 or 1.3 revolutions of the engine. I always thought is was the other way around.

Yep, Remember going to a 1.35 from a 1.5 is like running your car in a higher gear. Not lower as your thinking would have it. So the lower the gear ratio number the slower the engine will run all things being equal.It puts more load on the motor. The gear ratio from 1.5 to 1.35 is about the same as the 1.5 and 3" of pitch more. So a 1.35 with a 27p prop will run the same as a 1.5 with a 30p prop. All you need the ratio for is figuring slip if you care.
I need it because I dont want to run a 37p prop, it leaves me with not many options. So I went with 1.35 and a 34


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