I was having some idle issues and took it to the marina and they said I have a burnt valve.

I was wondering what it should cost to have my heads re-done or should I just go out and buy some new ones? I have seen stock heads out there for about $800 for the set. I am looking to go the cheapest route since I have spent a ton on the boat lately, but if I am doing it should I be looking to get something better than stock or am I am going be spending a lot more to upgrade??

I would recommend using a better valve than what is there. A set on Manley valves (SS intake, Inconel exhaust) will run about $500. If all of the other hardware is in good shape and doesn't have a ton of hours then re-use it. If it all needs to be replaced, then you will spend about $800-$900 on all new hardware (all better than stock). First, they need to figure out why it burned a valve before you spend money to fix it.
Eddie

Rocky, what did they do to determine you had a burnt valve???? Vacuum and leak down test maybe????
Until the head is off, its kind of limited as what you can tell is wrong. They would be able to determine which cylinder and which valve, but not necessarily what exactly happened or what is wrong with the valve.

First thing is to determine what caused the failure and exactly what is wrong. Using better valves can't hurt, but they can get pricey. I would plan on just redoing your heads.

They pulled the cover off to see if they could just adjust the valves but when that didnt work they did a compression test and found the it had very low compression on #5

Have them do a leak down to dertermine the cause of the low compression. It could have burned a valve, but it could have burned a piston as well. The leak down test will reveal where the problem lies. Once you figure out what the problem is, you need to find out why it happened, like I said before. You need to be sure that it won't happen again before you start throwing money at it. Good luck.
Eddie

It needs a leak down test, at least on that cylinder to determine exactly where the compression loss is going. Like eddie said, it could be a valve, piston or even just a head gasket. You could just pull the head and go from there. That also explains your idling issues over the Summer. Who is doing the work???? Berger's????