Have a 78 NOVA 250XL with mild 406s, 8.5-9:1 comp. thru hull exhaust, pre alphas 1.5 ratio, runs 4000rpm @ WOT 53mph, has 23p cleavers, thinking It needs to come up to around 5000 @ WOT. Just found a set of 21 cleavers that have been rebuilt, and refinished, going to try them, also checked the initial timing just to make sure they were both the same and it seems low @ 3 BTDC, did not do total yet, it has the old style mallory points centrifugal advance marine distributors in it. I'm hoping the total is low too, and can advance the initial to 8-10 BTDC and get around 34-36 total. The boat is on plane @ 2000 rpm and does it effortlessly, I am trying to take it easy on the pre alphas and have not nailed it out of the hole. it cruises @ 3000-3500 on the primaries @ 42-47 MPH, but once it gets to 4000 it hits a wall. Am I on the right track??? I am sure this thing should run 60-65....

Opinions??

sounds like timing. but you don't wanna go past 32 deg total. alpha lowers are cheap. it will take a lot to hit 60 with this hull though. pull dist caps and see if mech advance feels smooth and free.

I was able to advance the timing 12deg total to 32, trying the changes tomorrow

I timed both motors to 32deg total and gained 500 rpm, but only on one motor the port motor will not rev past 4K at WOT under load, I'm going to swap carbs from on side to the other, and see if it is carb issue. Next will be swapping the distributors they are the old points type Mallory marines. did manage to hit 55 on GPS. 21P props should be here this week, so with what they give me I should be able to spin them to close to 5K, just need to figure out why the other motor is dragging behind.

I don't think hitting 60 would be to terribly difficult. For reference I was a hair under 50 in mine, with 1200 hours on a pair of merc 188's and chewey alum. props. Just going to decent stainless props would have me over 50. One of you motors should have more hp than both of mine combined, If I knew then what I know now, when I redid the transom I would have raised the x a little and replaced the funky heavy engine mount tub with actual stringers.

replace the points with the pertonix kit.

I had a similar issue with my 85 Chris Craft Stinger 260. Somehow one of the hangers on the secondaries of the Quadrajet got bent and was not lifing the rod the proper amount.
Have you checked to see that the carb(s) is/are opening all the way? I had mildly warmed 355s - 350 + .030 and hit 62-63 with 23" clever 3-blades. The 21s way over spun the engines.
Can't imagine why you cannot pull the 23s to 5200-5300 unless your cam is WAY TOO small. Do you have high rise intakes?

Carbs are good, even ran the slow motors carb on my 68 BBC impala to check it, ran like a raped ape, I have ordered electronic ignition and it will be put in today, another test run tomorrow, the 21P cleavers got sent but were destroyed by the USPS so I can't try them this weekend. The intakes are the standard low rise cast iron units, and do not know the cam specs as the motors were done prior to me getting the boat.

Me thinks I found the problem, after exhausting every solution I could think of, I checked the drive ratios, marked both props, and turned the "normal" running motor over 1.5 times, and the prop turned once, turned the "slow" motor over 1.5 times and the prop turned just over 1 1/8 turns, so that leads me to think the slow motor has a 1.32:1 ratio? Hence the almost 1000rpm difference in the 2 motors. Am I on the right track??

has to be some weird combo of upper and lower. never heard of an under 1.5 pre alpha. quikie fix, get a shorter pitch prop for low geared side. 2 inches is 10 percent at 20 inches. so a 19 on one side and 21 on the other should do alright. even an alum junker 50 bucks on ebay. then start shopping for another drive...or two.