Probably not enough carburetor.

Plus, what exhaust?

With those heads and a good exhaust, I'd use something like the Crane 741. What pistons did you use? If you went from the stock dome to flat tops, you lost some CR. Where is the timing set at?

I'd borrow a set of 21's or 22's and see if that gives you some more RPM and gets you a MPH or two.

The deep drive is what it is- expensive to fix.

motor
 

Yea the drives are deep Still think should see more rpm it doesent struggle to get to 5k it goes there quick then stops even if I trim up way to much(on purpose). Stock exhaust for now but it was dynod that way wet with water pump and see pump made 520 hp at 5100 598 ft pnd torque at 3500 rpm. Seems like going to 22 would slow down mph. motor doesent bog at all from 4000 to 5000 and picks up 20 mph I think thats good isnt it?Seems like carb not big enough?A 23 pitch at 5000 rpm 1.5 drive 60 mph whats that slip ratio?

Oh yea pistons and comp are fine domes 116cc I think

Not sure on slip, could ebt he carbs, what is total timing set at?

I set the total timing a little conservitive at 34 the MSD dist has about 21 so base is 13- 14. Had detonation problems on other motors before and dont want it right out the box on a new motor. thanks Dan

One stupid question... is you trim limit set right? do the drives stop trimming too soon? bring both drives all the way up and see where they are before using trailer switch.... just a thought!!!

No not a trim issue Im not that goofy!

I hear ya, sometimes ya get all mixed up and forget stupid stuff!!

Do you have a set of carbs to try?? or like as said before, try a smaller prop, it should rev 200 or so more easily... not sure how to caculate prop slip..

Got a buddy that can figure prop slip Calling him latter As for carbs no extra big ones yet but Ill find some . Some one awhile back said the stock rochesters merc uses on ther 420 hp were just bairly enough wonder there cfm? and I got lots more cubes than them. Does your boat reach top speed and rpm quick or does it take a few more seconds .I throttle this one from 40mph and it goes you feel it set u back no it dont pin u back but you know its accelerating then its done at 5k !

420's should have had Holleys...

I have 460 CI with Melin heads, 420 cams still, Holley single plane intakes and Holley 750 (420) carbs, I just got the boat in 2 weeks ago after having issues wiping mains, all is good now but have not beat on it alot, I started to last weekend, went right to 5000 but i did not trim it much and did not hold it there long, engines are still kind of new and for the first time ever I am trigger shy.... usually I just run hard!!

I will PM you a site with all my info if interested...just search my user name..same as here.