502 HP ratings
#11
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Your logic isnt making sense.
#13
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Thread Starter
Sooooooooooooooooooooooo I always thought after 89 they were measured at the prop shaft, but what do I know,
Sooooooooooooooooooooooooo
my 93 502 carb was what at the propshaft?
potential new boat 94 502 EFI is what at the propshaft???
after we figure that all out when and if I get it I'll yank the motors go down to the hardware store and buy some blue paint
Sooooooooooooooooooooooooo
my 93 502 carb was what at the propshaft?
potential new boat 94 502 EFI is what at the propshaft???
after we figure that all out when and if I get it I'll yank the motors go down to the hardware store and buy some blue paint
#14
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I know that this horsepower rating information clarifications step on the capes of a lot of superman powerboaters but if you dyno a stock 502MPI at the prop you will see the real power at the prop. I believe Bob at full Throttle has done many such prop test power levels on his propshaft dyno and maybe he will be kind enough to reshare his findings.
Powerquest Baby, if it makes you fell better that a stock 502MPI makes 415 or 425hp at the prop have at it, I know what it really makes regardless of advertising or opinions here on OSO.
Best Regards,
Ray @ Raylar
Powerquest Baby, if it makes you fell better that a stock 502MPI makes 415 or 425hp at the prop have at it, I know what it really makes regardless of advertising or opinions here on OSO.
Best Regards,
Ray @ Raylar
#15
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I know that this horsepower rating information clarifications step on the capes of a lot of superman powerboaters but if you dyno a stock 502MPI at the prop you will see the real power at the prop. I believe Bob at full Throttle has done many such prop test power levels on his propshaft dyno and maybe he will be kind enough to reshare his findings.
Powerquest Baby, if it makes you fell better that a stock 502MPI makes 415 or 425hp at the prop have at it, I know what it really makes regardless of advertising or opinions here on OSO.
Best Regards,
Ray @ Raylar
Powerquest Baby, if it makes you fell better that a stock 502MPI makes 415 or 425hp at the prop have at it, I know what it really makes regardless of advertising or opinions here on OSO.
Best Regards,
Ray @ Raylar
#16
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#18
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Is this correct?
#19
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Mercruiser(black engines) are rated at the prop.
Mercury Racing(blue engines) are rated at the crank.
Note I said RATED.
#20
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Join Date: Aug 2005
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What is odd about the black engines is that Merc rates the 502 mag at 425 at the prop yet OMC rated the 502 at 425 crank and 385 prop. The OMC engine is the exact same engine! Plus I really doubt that the 454 mag carb is going to go from 365 crank to 385 prop with the addition of fuel injection and a slightly different cam. I'm with Raylar that its marketing hype vs reality. Look at a Merc manual for example, the cam specs are all over the place.
first going from 365 to 385 with injection and cam work is a piece of cake...
second my factory workshop manual for my late 502 says
425 and they make no mention where but the presumption has to be at the flywheel...
why would it make any sense to measure it thru a drive ? losses thru various drives would differ and just add a variable that would make the number meaningless in general... the spec would have to read " 425 hp at the prop thru a bravo 1 at 365 deg temp using 65wt saemc gear oil "
huh ?
i know its just bench racing... but it has to make sense to some degree...
and a 496 vs a 502 w/ a 10 hp dif " outperform " one another ? what does "outperform" mean ? accelleration ? top speed ? on paper you might think the one with more hp would have to be better but the shape of the curve vs the shape of the hull and the drag profile might mean that the higher hp motor never makes the revs necessary to get to where the hp is made because it can't push thru the drag to get there... in one hull one motor might be MUCH better and in another hull the opposite would be true...
and do they actually say " at the prop after the drive" or do they say " shaft hp" because shaft hp could easily be crank hp. when you dyno a specific car on a chassis dyno you might say ' at the rear wheels" but you can't then say that as a standard that motor makes that power at the rear wheels of EVERY car you put it in... just that one type and spec
just to fan the flames of discontent...
Last edited by stevesxm; 04-29-2012 at 07:19 AM.