I have had this engine built.. it is a 515 CI, was told it was 600hp. origionaly had a 454 thunderbolt 300hp running a 23 mirage plus at 4300 rpm 54mph.. now running this supposid 600hp with a 22p 4 blade at 4800rpm at 61mph.. the boat is a baja outlaw SSt 1996. bravo 1X upper and bravo XR lower 1.5 ratio... Thought it would be turning at least a 25 3 blade or a 26 4 blade. at 75 to 80 mph.... running stock corsa mufflers from baja that were with the 454 300hp engine that was in the boat......

please any one wiht any input would be greatly appreciated.




Build Sheet 515 CID
Base Engine 502 Chevy/Mercruiser
Component Description of Modification Parts Used
Block
Line hone, square deck bore and hone to matt 500 grit
finish. Install Campro sealed power cam bearings. Tap
and fit all threads and install all block plugs.
502 Gen V
Crankshaft
Stress relieved, radiused micro-polished to upper limits
to allow proper rod and main clearance. Cross drilled
and champhered oiling holes. Fit main bearings to
0.0028 and rod bearings to 0.0025. Rear main bearings
@ 0.0035.
GM forged 4.00” stroke, premium sealed
power bearings
Connecting Rods
Shot peened, size corrected for proper bearing fit. Fitted
with boron super alloy bolts.
GM forged 7/16” “Dimple Rods”,
premium sealed power bearings
Pistons and Rings
Pistons fitted to bore with 0.0058” clearance. File fit
rings to individual bores. Top gap fitted 0.024’. Second
gap fitted 0.026”
JE SRP premium forged aluminum
pistons p.n. 139483, sealed power
plasma hellfire rings 1/16, 1/16, 3/16
Cylinder Heads




~
Square surface correct chamber cc Fully port and
polished. Modify valve seats to accept oversized valves,
Intakes at 2.300 and exhaust at 1.880. Install bronze
valve guide liners and fit for positive seals. Set valve
heights intake and exhaust at 1.930 © 140 psi / 1.250
@39Opsi.
GM cast iron hi-performance ractangular
port. Manley stainless steel intake valves
p.n. 11530-8. Manley inconel exhaust
valves p.n. 11730-8. Comp cams valve
springs p.n. 930-16
Cam Shaft
Duration @ 0.050 lift mt - 236deg. ext - 242deg. Lobe
lift mt - 0.360, ext - 0.370. Lobe separation mt - 1 lOdeg,
ext - 1 IBdeg. Installed ~ I lOdeg mt ATOC.
Custom ground hydraulic roller p.n. HRT-
3001-3002-14-4R with matching
hydraulic roller tappets. Comp cams
retrofit push rods p.n. 7815-16.
Rocker Arms
Set at 0.00 plus 1/2 turn.
Procomp 1.7 ratio aluminum roller rocker
arms with posi-stop lock nuts.
Engine Oiling
Install oil pump and pickup to achieve proper clearance
in sump of pan.
~
Mellings hvfhp oil pump and pickup.
Dooley offshore 12 quart oil pan with
windage tray and trap door system.
Fuel System
Carburator fitted with 6.5 primary power valve and 6.5
secondary power valve. Factory primary jettiRg, 0.084
Intake manifold - Weiand team G rect
port. HP 850 CFM.DP performance

Notes: Optimum operating range 3200-4800 rpm. MAX 5200 rpm. does this sound correct

Maximum total ignition timing not to exceed 36 degrees before top dead center.


Any help on this would be greatly appreciated as this has been a total nightmere for 5 months now.

also will my stock 454 fuel pump be suffecient fuel delivery for this application.

thanks in advance.

Might want to move this out of the swap shop and into Q/A section.

I could not find where you mentioned what exhaust system you are using with the engine....???? I do not know what other factors could be hurting the performance of your new engine, but a stock Merc or poor breathing exhaust system will definately KILL the power making potential of your engine....especially when adding all kinds of induction mods....you have to let it breath just as well on the exhaust and especially if you are using a choking muffler system on top of a already bad breathing exhaust system....so, what kind of exhaust system are you using??? It is definately something to consider....just my .02

What size piston and what compression ???

4 inch stroke and 4.500 bore gives u 509 CI,with a 9.5:1 compression you should be ~ 600 + HP but u need to upgrade the exhaust to let it breath.
I think u are choking it .
Also it depends on cam,,,and it also depends if a car engine builder built it for u .
it may not even reach the powerband @ 4800 !!!!!

But hey ,,i am only guessing here ,but u need to check that stuff.

lift mt - 0.360, ext - 0.370. ???????????????thats all,we need to see the cam card from the cam,as mentioned stock exhaust would be a big choker..

just noticed stock fuel pump, my builder had me get the replacement half pump from cp which changes your lines to na 8= 1/2 from tank to carb where they went to na 6. fuel pressure was pre set from new pump not to go over 8pr.runs like 7 1/2.

As far as I can decypher, you're also running a 110 LSA Cam with .620" (+) lift. That's reversion territory unless you have CMIs or high risers.

Need more engine info; Comp ratio etc

I think he has cmi from talking to him a while ago. this has been restarted in the other thread general Q&A