Re: Can anyone help me?
my 21' sea hunt "Triton" is very similar to my friend's 21' sea pro, although ours are newer (c. 2003). I understand sea pro is out of business.
Ours were rigged with 150 Yam's, but mine is rated for 225 max. The weight is 2,100 and it has an 80 gallon tank; loaded it weighs around 3,500.
Your hull may be a different design, though, such as a bay boat, which may have a lower max HP.
$500 is a steal. Just be sure your transom is solid; I'd be worried about accumulated water in the stern if it's been sitting-is it funky in there, or clean? But mine accumulates no more than a pint of water (eyeballed) as the deck drains out the stern scuppers (be sure they aren't clogged, too).
I think you ought to install a garboard plug, and in doing so, you can inspect the intgrity of the transom. If it's OK in the bottom, I'd think it's OK all they way up, since as I said, the risk is from accumulated water at the bottom. If the transom is soft, you have plenty in your budget to replace it.
If it's been sitting a while, be sure to deal with the old fuel correctly; don't run it through your motor.
Welcome to Iboats and enjoy your boat! Post some pics when you can.