Hi i did not use the tabs, and this week i will try 4-blade 17,5x28,cleavers and drain out 200gal, of fuel before i try it again.

Now i have put the 2 inch spacers and 4-blade 17,5x28 cleavers,the engines are spinning 3000 rpm WOT 47mph still have difficulties to plane,think the max rpm is 6000-7000 rpm on these engines, gear ratio 1,5:1 ,what to do ????.

You will definately need to try smaller pitch props. It will get the engine into its power band. I would try something in the 22-24 pitch range.

Why do you think they are 6000-7000rpm motors???? Do you have dyno sheets???? With 620hp, 5500rpms is more likely.

Don´t have the dyno sheets, i pulled out the engines and i am going to supercharge them and do the dynos.

How did he get that from the Navy without holes being poked into it?

It had maybe 15-20 holes in the hull made by a forklift.

What gear ratios are in the outdrives? You should be able to spin more rpms than that with those props.

The gear ratio on my speedmaster#4 is 1,5:1

HP to weight ratio in theat boat should put you in the 70 mph range with 24 pitch propellers turning 5400.

Check your recomended engine rpm ratings. I think you may be a little high in 6-7000.

Because the propellers are now hooking up well enought to keep the slip % below 15, something must be going on with the engines to only allow 3000 rpm.