Sell what you have and buy what you want. You need to know how much Hp you want to make then you know what to buy.

Well, 4800 puts me at 51gps with a 1.5 ratio drive and an 19p prop. If I can't break 60 then I would rather stay where I am.

It should take around 200 hp to pick up 10mph if that helps .

and thats all dependant on your hull....some you could throw 500 at and not pick up 5 mph ! Rob

I upgraded a 20ft boat two winter ago that before/after was 55mph/68mph in same exact conditions/fuel load. Prop was maximized in before condition. Not quiet sure in after yet - still working on that.

Before: '91 5.7/260hp Mag that had better carb, arrestor, intake, exhaust than stock. Was running 3-4mph faster with these upgrades vs stock.

After: untouched shortblock from above - new heads, intake, cam. Same carb, flame arrestor, exhaust, and TbIV ignition.

Note: Would not go over 65-66 (all props tried would blow out right at 65-66) until I put a nosecone on the 1.5 Alpha drive. Bang - 68 with no prop blowout.

So, how do I know if I should open up the bottom end? It runs strong and burns almost no oil. Should I just do some top end goodies and let the bottom stay??

piece of mind... dont know about you, but I would hate to do a lot of top end work, then blow the rings thru the pan.

Thats kind of what I was originally thinking. Do the bottom now because it will be out of the boat. Ok, so... Lets make a list. Scat or eagle crank, cast it ok. Connecting rods. 5.7 or 6? Pistons, forged. Heads, performer rpm intake, 750cfm carb. What should I look for in a cam?

leave the engine alone and start with a different block.

98 pick up motor turned into 383 full scat parts eagle crank howard brown cam 530 lift not sure of duration vortech heads manley valves double spring valves com roller lifters apox 450 horse 22ft scarab alpha outdrive 72 gps no more than 30 degrees timing will melt already found that out engine builder said 650 demon or 650 quick fuel nothing bigger to much fuel if u go bigger hope this helps