Wow a L6 pushing a 24 footer and a nice boat also, worthy of keeping...
I can't speak for Bond-o, but i would think he would suggest going with a merc drive. Volvo would be even better i would hope he would say. Merc a little cheaper to up keep. Will be around for support, and parts are easy to get.
And that boat could do with more power, so lets explore this a little further.
That L6 will not push that boat very well, why it was put in there is beyond me.
So to cut to the quick best bet is to buy a boat that has a bad hull, in some way but with a V8 Merc package in good shape, pull your motor and drive. Then fix the transom to accept the merc package.
And you would have everything that would nickle and dime you to death on the donor boat.
In turn you can sell the good running L6 that people would pay dearly for. And the drive people would pay dearly for also.
This would mitigate the cost to you of the purchase of the donor boat.
I hope i was clear and if you have any more questions please post them.