15in. setback, propshaft height????

[Johnny Venomous]

I have a 30 Cobra Cat with twin 2.5's, I just bought 15" Rapid Jacks for it instead of the 5.5" CMC's that I had on it. My question is what height should I set the propshaft's at with the extra setback. I have not called Hydrodynamics yet, I just want to see what you guys think. :D :D :D

[capnzee]

I believe the water will rise 1" for every 12" behind the boat at around 70 mph. If you are 15 inches behind the pad and would like half of the prop shaft in the water, you would "jack" it up so that it was approximately 1 1/4 inches above the pad. This is a rough estimate and I am sure there are more informed sources who will speak out on this issue--it's a place to start.
Capnzee

[Jay Smith]

I have always used the formula for every 1" you go back you can go up 1/8" from split shaft..... In otherwords if you have a 8" plate you can ( in theory ) come up 8/8 ths or 1 " If have used this formula on many different configeration hulls and its been pretty close give or take 1/4"........You need to remember all hulls have thier own sweet spots and its got alot to do with the layup weights and the load its carrying...


Good luck !

Jay

[Tantrum]

Johnny, are you putting it together?
You better call me.

[Johnny Venomous]

Don't worry Chris, I'll make sure you and the boys are there to help. My pistons should be here at the begining of next week.


Jay,
Thanks for the formula (you are someone I trust to give me good info), When I had the 5.5" CMC's on I had the shafts up about 1.5" and I never really tried to go higher. ;)