Unable to get up on plane
 

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.

Re: Unable to get up on plane
 

Is your distributor advancing the timing when you give the engine throttle? Also, did the boat plane in the past? How much does the boat weigh? Pitch and condition of your prop? Did you recently change the outdrive by any chance?

Paul

Re: Unable to get up on plane
 

What is the max rpm at wide open throttle? And what was your performance before? Was it with the same prop as before? Or did you change?

Re: Unable to get up on plane
 

Something I found a few years back on one of my boats was that the end of the exhaust riser collapsed inside of the hose,,the motor ran smooth everything seemed fine but the boat had no power and wouldnt plane,,,took everything apart getting ready to change motors when I found the problem..just something else to look at.

Re: Unable to get up on plane
 

Also a basic but, it's not year old gas in it?

Re: Unable to get up on plane
 

Depending on the Prop, it may be the inner rubber hub that has come torn lose inside the prop. This would allow low rpm/load operation but under load will allow the prop to slip not being able to bite the water.

Just a thought.