Unable to get up on plane

Joined
Jun 25, 2012
Messages
7
I have a 1994 Mariah Talari with a 5.7L merc with thunderbolt IV ignition. The engine doesn't see to have enough power under load to put the boat on plane. I have done the following:

Change the distributor cap and rotor button.
Fuel Filter Change
Checked timing it was 8deg BTDC
Checked compression. Seven cylinders ranged from 140psi to 155psi and one cylinder was 135psi.
Checked Anti-Siphon Valve. It was working perfectly.
Checked voltage at alternator. 14.6V

Also when I had the spark plugs out to test compression they were very black, so I would think that the engine is burning rich.

Just wondering if anyone would have ideas on what the problem would be with power.

The next thing I'm going to try is a new ignition coil and spark plug wires. Can I use an igition coil and wire from a street GM350?
 
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