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post #13 of Old 02-18-2009
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Sounds like a worthy goal. I've been researching it also. If you don't have "Electric Propulsion for Boats" by Mathys you will be amazed at how much info he put together.

Did you every hear the one about how to identify the Pioneers. They are the people with the arrows in their back. There as so many, many things that can go wrong so a design will not work well. And then there are the things that work but will cost a lot more:
1. The motor you identified does not mention if it will run continuous at 100+ volts and put out the HP you need. Some folks have picked the motor and promptly burned them out as they may run at low volts for a long time but burn out in minutes at high volts
2. Saildog and Cam are the experts on battery, volts, amps etc conversions etc. but I'm pretty sure the battery holds a finite amount of power and converting to higher voltage makes it possible to use smaller cables but you only have so much power in a given battery and going to a dangerous voltage will not accomplish much.
3. I'm thinking that that Catalina 27 size boat might be near the max size as a Catalina 30 size boat will take a lot more HP to push.
4. One trick is to pick a flat day with no current and tow the target boat with powerboat and put a strain gage in the line to see how many lbs it takes. That would be ideal circumstances. Try it in a sea way and see the numbers shoot up.
5. You will need a new prop to get any reasonable efficiency.
6. Add up the: Motor, clutch (maybe), reduction gear, batteries, charger, regulator's, monitor, cables, and boat modifications to get your cost.
7. If you any expectations of selling the boat figure on a sale price that includes no motor.
8. Figure on significant limitations on distance and if you get caught in a squall and want to power off some rocks make sure you have full batteries and the squall is over in maybe 30 minutes.
9. Calculate the life of each part compared to a diesel.
10. And of course anything you buy this year will be considered quaint and a 'good effort' just five years from now.

Despite all of the above if I could get a Catalina 27 size boat and do 4 knots for 10 hours at 50% and full power for an hour before having to plug into shore power and get it installed for $5,000 and figure it would give me 10 years service and not take up all my stowage space I would consider it. It would be way cool as my wife is allergic to diesel. Unfortunately I suspect it will cost a bit more than that for now. The realistic problem is that you have to commit to this process as a life-style as you will be tinkering with it for hours on end, it will not go smoothly as you are a pioneer and their is precious little to go on.

Last edited by davidpm; 02-18-2009 at 11:37 PM.
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