hp after rebuild merc 502
 

hello guys,

I have my mercruiser 502 rebuild. gen v

new srp pistons(by JE) dome
heads valvejob.
compression now 10.8 (in the netherlands we run 95 octane so this is no problem).

The engine is bored an honed to a 509
k1 Connecting rods
and a new comp cams cam http://www.compcams.com/Company/CC/c...?csid=404&sb=2

does anyone have an idee on what hp this will make..

i am now doing testruns but i have only have won 1mph on top speed so far.

we are now looking to set te timing again, maybe there ar some hp hidden...

that is similar to a hp 500 cam depending on how what work you did to the heads plus the extra compression ratio i would think 550 hp range would be close maybe a little less, whats size prop did you and are you using now at what rpm? is it fuel injection or carb?

it is a carb , edelbrock 750.

heads: new valves and flattend
intake original. exhaust thru hull, headers original.

i run a revolution 25p at about 5100 rpm( same prop as before rebuild). i have tried an mirage plus 23. but got the same rpm also tried a bravo 26. but only got to 4700 rpm. speed almost the same with al three props, acceleration was the biggest difference.

also the engine temperature was getting a bit high at high rpm, about 200F
we thought the timing might be off a slight bit with should explain the higher temp and lack of hp.

any other ideas are welcome

The cam is a flat tappet, slightly larger than the old Merc 420 cam.
How much timing are you running? Carb jetting?

if i am correct it is set at the timing according to compcams recommendation. i am not sure how much timing this is.
by carb jetting you mean more or less fuel?

the revision company has set the motor up

I have almost the exact same motor/setup.
I run a 24 up to 5k rpm, base timing set at 11*, edelbrock 750 w/the jet kit (replacing the needles making it set 1-2 on the rich side). 160* thermostat. Out of the box the carb will probably run ok, but I would double check and make 100% sure it won't run lean and @ WOT fuel psi is still 6-8. Very important, don't forget fuel delivery to the carb!
With 4 batteries, 1/2 tank fuel and gear, I can hit 68-70mph per gps. I believe like stated motor is basically a hp500.
You won't know true hp results unless you dyno and then consider/factor drive loss to actual hp @ the prop. Hope this helps for comparsion.

this does help! thanks!

i shall test the carb as well

You should have no problem getting 550hp from a fresh 502. (Especially with that compressiThat carb is way too small for that engine. You need an 850.

How do you use the boat? Cruising, running wide open, racing?

I was thinking the carb may be a little small as well. Hmmmm, maybe time to find an upgrade.