Engine bogs down under full throttle

"I have an 86 Four Winns with

"I have an 86 Four Winns with 170 hp. mercruiser. Just got it out and tuned up, new points, condenser,fuel filter, etc... Runs great up to about 25 mph but any more throttle than that and engine bogs down. My prop is horrible.. I'm talking pieces are missing it's so bad. Just bought a new one and will replace it this weekend. My question is this, I was told that a beat up prop like that will cause the engine to bog down under load, true or not? Someone else told me maybe it's water in the gas but why would it only bog down under load and not all the time? Same with any other fuel problem, you'd think it would happen all the time. Anyways, just wondering if anybody else has had this happen and putting a new prop on solved it? Thanks for your time."

"Change the prop first and see

"Change the prop first and see how it behaves. If the problem persists, then its time to troubleshoot.

Cauliflower prop blades cause a world of trouble.
Even small looking imperfections completely destroy the smooth laminar flow of water over the blades.

Rod"

Rod is right on with the prop.

Rod is right on with the prop. It causes heavy cavitation which makes the prop to be trying to push thru air bubbles. A buggered prop is also out of balance and not good for the prop shaft assy.