Boat is crabbing and blows out at 95mph

[H20JIM]

Made the second run with my new liberator 18 3 seater yesterday and found that the boat will crab slightly untill about 95 or 100 and the prop blows out. Motor is a 300 promax, 12" set back, torquemaster 1.62 w/built in wedge in the skeg, Bobs cone and a 32 ET. The boat is a mid 600lb hull. Right now I have the centerline of the prop 1/8th up from the pad.

My initial thought is that with the weight of the 3.0L and the 12" setback I need to come up with the case. A buddy has suggested that there may need to be more of a wedge in the skeg than what the stock case has to offer.

Any and all opinions welcome.

Thanks in advance,
Jim

[specboatops]

I'm thinking you would want the sportsmaster rather than the torque master too.....................

[joed]

Its paddle wheeling ,lower the motor 1/8 inch at a time until it quits. You don`t want many of those 100 mph blow outs. 12 inches sound like a lot
I have 9 inches. One of the very successful Mirage drag racers swears by 8 inches of setback. Good luck and keep us posted.

[beer30]

Call Randy( Wildman) at Liberator Boats in Daytona. He made a few of these fly.:thumbsup: Chuck

[H20JIM]

I have been told that the coned TM is actually a faster case than the Sportmaster.

Joed ~ You think it needs to go down with the added weight and setback? I assume you are referring to Jay on the mirage. He has told me that the angle of water off the pad is 30 degrees, which would put the water level well over the top of the bullet on the case.

Chuck ~ I talked with Randy. He has had good luck with this combo , but he ran a 10". I think he told me he was running 3/4 to 1" up?

Thanks for the help, keep those ideas coming.

Jim

[stokernick]

I may be wrong but crabbing means you're too high,thus paddle wheeling!3 blade or 4 blade prop?

[Hot Shot Merc]

I dont see how beeing only 1/8TH above the pad with that much setback could be considered too high?.Hell, 1/8 inch higher with zero setback is not too high. I run 1 1/8 above on the q shot and going to raise it another 1/8.

[H20JIM]

I'm with you Rob. I'm going to raise it a 1/4 at a timeand see how it feels. BTW its a 3 blade
Jim

[Wizard]

Too much setback for a Mirage. That much leverage means the nose will run high. I'd run no more than 6" on an 18ft tunnel.

[Hot Shot Merc]

:cheers:
Too much setback for a Mirage. That much leverage means the nose will run high. I'd run no more than 6" on an 18ft tunnel.A lot of guys prefer 8".I think with the weight of the motor(300) the extra set back helps balance or (center of gravity) the boat better.Just an opinion

[WILDMAN]

I ran this 18 Liberator with a 300x and a 32" Lightning ET. I used 12" setback and 1" above the bottom. I only opened it up once and took it to 117 on GPS at 6750 rpm. You need a sportmaster. I tried running with a coned torquemaster and it would also crab. You don't have enought torque tab. This 18 was a 900 lb. very thick hull. That's why it sits so flat. I think if you swap cases and raise the motor, you'll love the boat. The blowout is most likely because of the crabbing making the skeg go though the water sideways.

http://i158.photobucket.com/albums/t117/Randycorson/Purple18withJoe-1.jpg

[H20JIM]

thanks Randy. I thought you told me you ran this combo. I'm going to raise it up and try that before switching cases. I've got too much $ in this case to not try it.

[WILDMAN]

It may work if you put a bigger tab on it. You got any friends that will loan you a sporty to try?

[whipper]

If your crabbing it may not be that your to high but rather to low and your compensating with to much pos trim also but i doubt it? Usually though its a combination of to high of gear case and to much trim. The design of the skeg and or the propeller design in relation to the hulls for efficiency. If you cant try a differant case try a differant prop like a 4 blade drag 4. When I'm testing new props ill trim until I crab or my bow drops a bit and the rpm goes up and the speed doesn't. Then I bump down once and I'm as fast as i can be. You need good concentration and water for this. Sounds like Randy has the answer though. He would know.:thumbsup:

[H20JIM]

Not many 3.0L around me to borrow from. I'll test on Tues. and report back,
Jim

[Roddles]

could it be the nose cone shape.You do have a nose cone dont you?

[Roddles]

We had our raceboat maxing out at 98 mph with blowout.We re-shaped the nosecone and presto 103 mph was our new top speed

[baja200merk]

my omc case does this on mine every now and then it will blow out cause of my tiny little skeg.. i think thats why its faster with 3 people then it is with 1 :rolleyes: