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the op didnt say what year his engines are but unless they are gen6s he will need retrofit lifters,different length pushrods and should modify the heads for 7/16 rocker arm studs as the vortec heads use non adjustable rockers,at this point his 1500.is gone and he still has an engine with cast internals.now he will need to upgrade his exhaust system for the cam he will need to make 400 hp.it just does not sound cost effective to me.

The 454 and 502 mags had the same exhaust as the 330HP. The 224/224 cam on a 115lsa should be no where near reversion. However, it is a step up from the stock 214/218 flat tappet . Pretty sure he can reuse his rocker studs from his 330 heads.

Many years back the 330HP Mercs were in a lot of boats. in the early days of OSO, there were a lot of guys running hopped up 330 merc's. Making 400, 450+ Hp out of them. If they kept the RPM within reason, they held up very well. Heck, some guys even had mounted small blowers on them and ran 4psi of boost with good luck.

Granted its not ideal as having forged internals, for an engine making less than 1hp per ci and kept at 5000RPM and under, its fine.

if my wife says black ,i'll say white.Life's no fun if we all just agree.
I agree there are a lot better bases to start with .But i disagree as to "not worth doing".If he doesn't spin the hell out of the motors,they will live
Do we know what exhaust he has ? I know he said motors are stock .

Clear your inbox, need to send you a pm please

try again buddy

What Mild Thunder and MOTOR have mentioned is more of what I am looking to do. The only thing I get nervous about with the L29 heads is the valves. I have a friend that has done this but dropped a valve after the third season on his engine. How do I tell if the stock valves are Inconel or not?

I am not against doing an engine swap to a better platform but I have seen first-hand good results with mild modifications other than the dropped valve but you can’t tell me a 502 or anything else hasn’t had the same thing happen to it.

To be honest it’s just a boat with no sentimental value so if I want to go that much faster I would be better off selling and taking that extra 6g with me to buy a different boat better equipped

im not saying the manifolds are different,im saying that to make a notacible difference in performance he will need a cam with more lift&duration than the 502 mpi roller from a gen 6 engine.back about 100 years ago we made mods to 330s in the jetboats because we had no money for better,bigger engines and exhaust was basset headers that were dry untill 2200 rpm.i agree that 400 hp can be had from a 330 but at the end of the day it,s still not a desirable engine.with the price of good used takeout engines plus what he can sell his 330s for,its a no brainer IMO.

and thats all i have to say on this one fellas,LOL.

My engine is a rebuilt 330 bottom end with, all ARP bolts, 088 heads, small Isky cam, roller rockers, Edelbrock intake and carb. I blew the original 330 2 weeks after I purchased my boat so I did not have money to spend on a better engine, and I built that engine on a budget. Made 407hp on the dyno and I don't run past 4800rpm. I only gained 2mph. I have been running this one for 3 seasons now and runs great but I got the itch for more speed and plan on saving money and building another engine in a few years.