I really wouldn't try that in a boat motor, maybe the lawnmower. What can go wrong if your lawnmower quits half way through cutting, 2 layered lawn. In a boat, hmm, better not need to row, row row your boat and then do a fuel system fix.
A few years back, I used the blue marine stabil in a can of gas, next spring there was a massive blue "jello" blob in the bottom of the gas can. Never again.