He's strong enough to use manual brakes. 5'11" 230

Cab- don't forget vacuum boosted brakes don't push easily without vacuum because of their design. But a manual setup properly should be just fine. It will require more force than a vacuum set up but not nearly as much as a vacuum set up with the engine not running. Haven't weighed it but I imagine this boat is over 4k lbs.

The main reason I'm thinking of converting to manual is for drag racing in the future. If he ever builds any sort of engine with a cam and poor vacuum, then inconsistent brakes would become an issue.

I guess the simplest thing would be to just fix the stock setup that's there now. Won't have to worry about getting the right mounting bracket, pushrod, master cylinder etc. Brake lines to the MC look fine now so they could stay the same if he stays with the stock boosted setup but would have to be redone if the master cylinder was mounted directly to the firewall.

Thanks all!