I have a 1979 Scarab 300 w/454's recently rebuilt to 600hp it has TRS drives (I belive 1.5 ratio) and currently running 23" 3 blade Cleavers it is running 51mph(GPS) at 4000rpm which gives it a 12% slip.

I have a Scarab III with 600 hp, TRS BorgWarner Trans.. Ran, upper 70's spinning 27" pitch Hydromotive Q-4's

The slip # is fine for the boat. It looks like you need to go down 2 inches of pitch to save the engines life.

Brett

Ok Thanks for the advice

I had a 78 Scarab 300 w/ twin 650hp, TRS and ran 27P 3 blade Mirage props. On the best day I got 82 on GPS. 79 with 26P 4 blade Hydromotives. Both at 5500 RPM.

With 600HP in that boat you should be running in the upper 70's maybe 80's spinning 27's. I had Merc 425's in my Scarab which has a similar bottom as yours and I was spinning 25's at 71mph. Now I have 590HP and looking to step up to some 27's in the near future.

What RPM did your power dyno at? and what mods did you do to get 600HP, (blower)? just curious not to many 600HP 454's out there anymore.
Jason

Not for sure what all was done the engines were built by the Guy's from the old Wayne County Speed Shop (if you are familiar with drag racing they were the Dodge factory Pro Stock team) I grew up about 5 blocks from their shop and swept the floors as a summer job when I was a kid.

DanJ,

Your motors should be spinning around 5000+ rpm.
With 600 hp per side on the motors, that boat should easily be over 75 mph.
Something is drastically wrong with the motors.
Stock 310 hp 454's should pust that boat into the 60's

Sorry to rain on your parade... just look at the motors, and make sure they are running right.

Even with 1.35 outdrive ratio, you should be in the 60's with those props.

Chris

P.S. I know that your boat is old-school technology, but 600hp pushed my 28ft boat to 83 mph... something just doesn't add up with your combo.

4000 rpm?? RPM is off the mark??

If they are wayne county motors you must have forgot to turn on the NOS thats the only way they made their engines run.