Dual Miniature Surface Drives for 12' Catamaran?

[aggieh20]

Hello, I am new to the thread. I am building a miniature offshore racing catamaran that has a single stepped hull. It is being built from fiberglass. LOA is 11' 6" and has a beam of 4'. Step is 1/4" that is located 54" from stern.

I am wanting to run a 80hp twin cylinder Kawasaki 750cc jetski engine mounted in the center of the boat. I have designed a pulley system to run two surface drives. They can be counter rotating or rotate the same direction. I plan on running the new three blade go devil props.

Question 1.How can I calculate the correct angle and or location that the drives need to be in so that I am not cutting holes time and time again in my hull to get it right?

Question 2.Is it feasible to not run counter rotating props since there is not a three blade prop available in the counter rotating form from go devil?

[fishon91]

can't help you with your first question, but i notice that these guys (a reputable surface drive,not mud boat, company) use counter rotation, and use a different style prop. i know more about go-devil than i do about arneson, a weed shearing prop is probably not what you are gonna want to race offshore.

i can say that you are making a good decision using surface drive, just make sure you get it all set right or it'll be pointless.

show pics when you're done please

[Frosty]

You must use counter rotation. I don't like the sound of your pully idea ,can you show Pics, 80HP is a bit much for belt unless you mean toothed belt!!!

Angle is 0 if you can get it, the configuration of the boat and your drive will be the decisive factor for that. 5 will be ok.

Don't skimp on shaft thickness, what are you think on rudders? Or rudder.

[aggieh20]

I have not yet decided on steering. I am in the process of designing a unit similar to arneson that allows for the surface drive to turn. I will be able to set the drives at any angle I choose. Will post pics when further along. Thank you for the input.