Underpropped???
 

Hey guys. I'm relatively new to big power boats, and just purchased a new to me boat. Boat is a 1999 Scarab AVS 38'... partial kevlar layup. Boat has 500 EFIs with Alexi @ Boostpowers throttle bodies, spacers, computers, etc. Shorties with 26 pitch labbed Bravo 1s.

Boat is an absolute pig coming out of the hole. Requires all the tab possible and blows the props out at the lightest touch of the throttle. I have to bring her up hard in the R's, wait for the props to catch up and hope that the boat starts to lay over while I bring the tabs up. It takes 20 seconds to get up and level out.

Once up the boat tachs hard.... 4000 RPM at around 50 MPH.... WOT which is around 5500-5700 gets me 73 MPH fulll load of fuel and people. Boat is certainly not underpowered.

What should I do prop wise? Any input here?

Sounds like you need 28p Mirages.....but there are a few VERY sharp pro guys around here when they notice your thread....But you have to be careful with the props on these Scarabs.....very heavy boats

I am no expert here, but I wouldn't think more pitch would help it come out of the hole quicker. The prop calculator indicates almost 22% slip at 5700. Makes me wonder if the set up is right. Does it have shorty lower units? Perhaps 5 blade props would be better. I would call Bblades or Throttle up. Either one will send you in the right direction.

I see you mentioned shortys in your first post,are they 1" or 2" short,I would try some spacers,Smitty

The boat does have 2" shortie lowers. Don't get me wrong, the boat runs well once up, but it just tachs way way to hard and to easily for my taste. I need to get cruise RPMs down 500-700 RPM easy. Can I stick with Bravo's and go up? I have a local guy with a set of 30's and 32's I'm welcome to try. Is this to aggressive?

It's the shorties make the planning difficult. Go up 2".

The props were labbed, was all of the cupping removed? 26 pitch props on that boat should go 80mph with lower rpm and better slip numbers. I would try, in order, adding cup to the props, or 5 blade props at 25 pitch, or spacing the drives back down.

Get the props back down in the water. They can't make power if they're not pushing water. That's why they blow out so easily. You will probly need those 28's too but get the 26's down in the water and go from there.

My guess is the last owner had the same problem and to cure it he went down in pitch hoping for better hole shot. May have helped some but now too many revs on top. Deeper drives and more pitch.

I would talk to the prop experts, but I think going to 5 blades should cure your problems. It will get the boat on plane faster, lower your slip numbers, and still let you keep the drives higher for more top end.





Darrell.

It sounds like 5 blades are worth a try. They should help with getting on plane and also reducing slip. BBlades has a swap program that offers great value. He should also be able to get you close to your target RPM at WOT on the first try. If you can get on plane, the X isn't too high. I would work on other aspects and only drop the X as a last resort....it will scrub speed.
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