I ran into a very similar issue and it ended up being a hairline crack on one of my spark plugs.

I know the boat is solid. The previous owner replaced all the stringers and transom. This weekend we are going to go through it better.

I had a 85 272, throttle cables were stretched. This kept carbs from going wide open.

[I]s this his first boat ? Or first boat with trim ?

He had a 17' sunbird with 130hp alpha one. He ran that last year. This is his first performance boat. I am going to visit him this weekend. I am gonna run the crap out of it for him.

He said that's trimmed all the way up. I wonder if his trim limit switch is set real low. I'm gonna check into that. Maybe bump the trailer button while running it.

Solved!!! Choke was not opening 100%. That would not allow the secondaries to open at all.

Not Solved! (My boat)....Secondaries are opening and getting more RPM now but still wasn't able to hit 50....49 MPH@4800, trimmed about 3/4 (seemed like the best run, more trim and she dogged out) tabs up.

Fuel still maybe? Sittin about 1/2 tank of 1 yr old + go-go juice...

Timing was perfect (10 degrees)....79formula calculated me at 19% prop slip....HELP

How is the bottom, clean and smooth, no bottom paint? What is the diameter of that prop?

No bottom paint, smooth as a baby's ass however I did discover today that I have the Formula "hook". My buddy has had his removed so I think this is costing me some top end.

Running a 21p. Going to try a 21 plus in the next few weeks. I'm told this should yield a few mph