Join Date: Oct 2009
Location: Gloucester, MA
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To get us in the ballpark, I will assume that 5hp will push you to hull speed(this might be low depending on the boat) which is 3.7KW. To run 30 hours, you need to store 111kWhrs of electricity. The storage required for this would not come even close to your weight or space requirements. It is also way too big of a system to charge without an enormous solar array which is not possible in this case.
To recharge this, if you do it over 10 hours (this is quite a while if you can't charge at your own slip), you would be charging at 50A @ 220V not accounting for any inefficiencies. This is impractical so you would probably have to double the charge time.
If there is a solution to this, it is going to have to be out of the box. I am not a fan at all of hybrid electric propulsion systems for boats unless they are used to extend range in rare circumstances on a truly electric system. These systems are less efficient, have more stuff to go wrong, etc. The reason why hydrogen was hyped for so long is that it is a reasonable media in which to transfer energy quickly. Too bad it is not in the realm of practical for a project like this.