Not sure about run time though. Most electric only lakes wouldn't allow you to have a gas powered generator on board, and $4500 plus labor is still a bit steep for the average jon-boat fisherman.
That said.... I hope the advancements made in the electric car industy spills over to boats. It would be nice to have a reliable 15hp electric only motor that could run 6-8 hours without having 8 12V batteries on board.
Wait until the price of Lithium Ion marine batteries comes down. Your options for faster electric motors are going to open up significantly. Won't be but a few more years, at that.