[Bluesman]

One way to cure the problem, and I am not joking.
Two 12vdc batteries can be configured in a series connection for a 24 volt momentary start voltage to the starter. Once the ignition springs back to accessory, the relay you have to install and wire will switch the two batteries in parallel for a beefy 12 volt system. In your case, you probably won't really need to do this. I have seen it done on real high compression motors.
I changed out my starter a few years ago to a high torque gear reduction starter. It weighs 50% less than the stock boat anchor
I had before.