72" Twin Electric Motor Cat Build Need Help

[Barry S]

Ok. I'm building a 72" Cat and I want to use twin electric motors. This is my first from scratch build and I need help in determining the size motors and esc to use. The build is nowhere near complete but I'm trying to look ahead for sizing. I'm not trying to win speed contests but I would like for a 40 to 60 mph boat. I just need a kick in the right direction. Also I don't want to spend an arm and a leg on them...just an arm.

[Doby]

Budget=??

[Fluid]

Run time expectations? Plus there is a big difference between 40 and 60 mph with a boat this size. We want to help but need more guidance. As Doby asks, how much does your arm cost? Mine is worth upwards of $5000.....



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[Barry S]

First I'm not real tight on budget so I'm open to any suggestions. I know I'm gonna have a good deal of money in the motors and escs. I'm going with an old school build of light weight ply but I know that I'm gonna be on the heavier side of most builds. At this point in the build I can not estimate an approximate weight. If I had to guess a weight I'd say about 30 lbs but I'm going to lighten it as much as I can. With that being said if I can get her to plane out and run at 40ish mph I'd be tickled pink. I can play with it from there. But I have absolutely no experience with this size boat. But I'm sure I want to go with electric and would like about 15-20 min runtime.

[Barry S]

A couple of pics

[Lone-Wolf]

Since you are not worried about crazy speeds I would look at this TP 5860 470Kv motor. A very good motor for $250.

For esc's I would check out the Flier 400 amp model, I have two of them and they are proving to be pretty robust and can handle the power demands of a larger boat, one of mine is currently in a 72" Mono running 16S3P with no problems and I have also had both installed in my 54" Cat doing well over 100mph. These esc's can be found for under $300 each. Next step up will be MGM 40063's but they will cost both arms and legs at least ;-)

The runtime you seek will be the hard part, as you can imagine these big boats need alot of juice, I think 10 minutes of runtime with the above setup and 12S2P/motor to start should be in the ballpark with Octura X457's but you won't really know until you get the hull in the water and see how wet/aired out it's running. A well balanced hull with that setup vs. the same hull running wet will be a huge difference in speeds and a huge drop in runtime and stress on the electronics.

Nice looking build so far!

[Barry S]

Thanks! The info you shared is gonna give me a good start in the right direction. I'm traveling to Belgium for work so I'll be off here for a few weeks but when I continue the build I may have more questions. Thanks for all the help!