PatriYacht

I bought a Black Thunder with a wild engine combination. 540 ci, Cam Motion solid roller 248/253 dur. 690 lift 112 center. Holley Pro Rams with 2-750 dp's. Msd ignition. With extension boxes and labbed 24 bravo 1's the boat goes 69 mph at 5000 rpm. Empty or 7 people and 1000 lbs of fuel same speed. Seems very odd to me.

SLINGSHOT

YOUR HP IS WAY LOW WITH 24 P BRAVOS....WHAT ARE THE RPMS SUPPOSED TO BE
THEY SHOULD BE SCREAMING

Tinkerer

Do the MSD boxes have rev limiters by chance ??
See if they have a 5000 rpm chip in them.
I would think that you should be able to hit 5600 to 5800 rpm real easy.

PatriYacht

6000 rpm chip. And I should add, the previous owner said it had 8.5 to 1 comp. Is it a bad combination?

mcollinstn

What heads?
Compression is on the low side for sure.
Is this a 43'er??

Have you checked to see if the carbs are opening all the way? Wide open throttle fuel pressure? Do you know what your ignition timing is at WOT? How do the plugs look after 10 seconds wide open?

PatriYacht

The heads are GM iron sq. port pocket ported and intake matched by Tyler Crockett. 2.25 intakes.

It is a 43.

The carbs do open all the way. It doesn't seem to matter though., the boat does't go faster it just makes more noise.

The ignition timing is 16 at idle and 36 at 3000.

Plugs are a little rich if anything.

The engines do burn a quart of oil about every 4 hours.

DonMan

The cam sounds too big for that low of compression. You would gain power with a smaller cam or raise compression to match cam / carbs. Then start buying high octane fuel..............

johnnyboatman

iTrader: (5)

what gear ratio in drives.

Tinkerer

YOU do have the tabs up and the drives trimed - right.
Please don't shoot me - we do get those problems sometimes.

PatriYacht

The drives are 1.5. The compression may even be lower. That's just what the owner told me. He had blowers on it but got tired of blowing up outdrives.