outboard-is there a set back to lift ratio?

[starcraft'76]

I have a '76 starcraft chieftain, 18 ft. with a johnson 115,I am putting a cmc trim/tilt on it,the factory one is bleeding down and the cost is the same for stock rebuilt or the cmc.I thought I may as well go for the set back, I've heard it can improve the ride.I will have a 6 inch set back and was wondering if the 3 back and 1 up I was told sounds about right to start with.I am also trying to eliminate high speed porposing,by my speedo it only does about38mph. I put 11x12 hyd trim tabs on and that helped alot,but I'm hoping a set back will improve perf. a little more.Any info is appreciated

 

[steelespike]

Re: outboard-is there a set back to lift ratio?

I'm sure no setback expert but I would think that there is no set formula and at best 3 back one up is a typical figure.Actual ratio would depend heavily on the boat,motor and prop.

 

[Dhadley]

Re: outboard-is there a set back to lift ratio?

The (very) general rule of thumb is for every 5" you go back you can go up 1". A lot depends on the actual transom angle and bottom design. A lot of set backs have angles built in so if the one you choose does then you need to consider that.

 

[starcraft'76]

Re: outboard-is there a set back to lift ratio?

Thank you for the info,I now know a couple of things to look for and consider when I put this tilt on.
remember if your boat doesn't get your money your kids will,and they'll just waist it