I would at a minimum change the cam. As other's have said, kind of depends on what you want to do with it.

So I picked up an 850 double pumper off of ebay, but when I checked the numbers on it it's only an 800. I had an Edelbrock 750 on there and it topped out at about 4k-4200 rpm. Is the 800 going to make any difference or should I find an 850?

An 800cfm is more than enough. Is it a USCG approved marine carb????

Don't forget the correct oil bypass valve!!
 

Rooster, pretty sure you said this block is a Gen VI, with the one-piece main seal. If that is the case, you absolutely have to make sure that the 30 lb oil filter bypass has been installed in the filter pad area on the block, or that it has been blocked off. If the stock 11 lb unit was left in there, then oil will bypass the remote filter and oil cooler in the boat because of the increased back pressure. Then you will have hot, dirty oil going through your engine, and your bearings will not be long for this world. If this engine was directed at the automotive hot rod crowd, chances are it has the 11 lb valve in it. No real way to tell which valve is in it just by looking at it - I don't think there is a part number that is visible once it is installed.

More info on this thread => http://www.offshoreonly.com/forums/g...ef-valves.html

Once again, you will probably be much happier with a stock 454 mag or 502 in this particular boat. It's no fun getting towed in on the water, or having your boat home on the trailer all summer while everyone else is out enjoying theirs. Good luck whichever direction you decide to go.

Yes.