Hey Jim,
My name is Hans. I have a boat slightly bigger than yours at about 11000lbs. I use a 48v with a brushed etek setup and chain drive reduction. What you propose should work fine. The motor mount will be no problem if you have a good mechanical aptitude. You can easily fabricate something from 1/4" aluminum plate and angle stock. 36volts should be plenty of power for your boat.
The only issue you have with your proposed plan is your target rpm range. Atomic 4's spin small props fast. Not very efficient. It is definitely more efficient to turn a larger prop slower. With electric boats you want to get every bit of efficiency you can out of the electrons in your batteries, cuz the batteries we have today don't hold as many as we'd like!
For efficiency you would be best off turning a larger three blade prop at around 1000 rpm. This might be a tall order with direct drive from the mars PMAC. I think the volt/ rpm ratio yields higher rpm at 36v. You would have to check. Another motor I would be biased for
would be the etek RT. It is capable of much more power than you would
need for your boat, but it can be run at 36 volts and I think has an
rpm curve that would work well for direct drive at 36 volts. Just food for thought.
That said, I think people on this group have done exactly what you propose: spinning the original atomic four two blade prop with direct drive and a mars or original etek. Very simple and affordable. You could search the archives. For your needs, maybe a good option.
Good luck,
Hans
--- On Sat, 10/10/09, JamesM <jg_martis@yahoo.
From: JamesM <jg_martis@yahoo.
Subject: [Electric Boats] Need Help: 26'sailboat Mars PMAC replacing Atomic 4
To: electricboats@
Date: Saturday, October 10, 2009, 5:34 PM
I am considering repowering (Atomic 4) my 26' 6000lbs sailboat with a Mars PMAC. I will be using the boat for costal cruising on Lake Erie, the need for power would be getting in and out of the docks. I am thinking a Mars PMAC with 250A Sevcon programable regen controller, 2 banks of 3 batteries running at 36 volts. using a direct drive and the 50volt/rpn constant that would max out at 1800 RPM.
Even though I have a good understanding of electrics and a basic understanding of electronics, I have an above average mechanical ability as I have repaired everything from cars to hospital ventilators.
Questions:
Will a 36 volt system work?
Do I need a gear reduction?
What are the advantages of timing belt over chain?
Does anybody make a motor mount that costs less than $4000?
What am I missing?
Thanks for your help
jim
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