Prochargers is least expensive way to go & easiest on the drives. Whipples will give you more low end power along with the fun on changing / repairing drives

Leave the engines alone and invest in a set of billet Hering propellers. You'll get the power you already have to the water without compromising the longevity of your engines.

Those motors have no problem holding 650+hp. Same heads as the 500hp efi, 500hp carb, 575sci. All have made more power in long term applications. Only a valve change and thats about all the difference is between 500hp efi and 502 mag heads.

It's going to take more than $10,000 though, even with PC's, and yes, the computer HAS to be reprogrammed. PC's 60-80psi range is not very accurate. Also, when you run a stock ECM cal at 90-110deg F engine temp, it will be adding about 30% more fuel, does wonders for the rings and bearings :D So the cal has to be part of the kit or done by someone that knows what they're doing.

Upper gears will fail first. For long term, you need a Mercury XR, but the stock drives will certainly make it for awhile with some semi-cautious driving. I've seen stock drives make it past 300 hours at 600-625hp. A PC can break the drive as well.

Blowers will give yopu the biggest power boost for money spent but as far as the budget your talking no matter weather you buy prochargers or whipples you will end up spending MUCH more than your planning. Stock 502 oil coolers are too small for long duration runs with extra heat from the extra power,custom tuning will be required for either kind of blower and if its not done correctly at a minimum it will run rich and sluggish and worse case it will be lean somewhere and you'll hurt a motor. Sooner or later you will eat up the drives,as stated,the upper gear will usually fail first,i ran a stock 2000 bravo in my single engine boat with over 600 hp for 2 seasons,I upped the boost and prop and got the tune pretty good and it almost immediatle sheared the floor out of a stock upper gear.
Power boat mag did a pretty realistic upgrade on a 38 foot fountain a few years ago,pulled the heads and went thru them,added better exhaust,upgraded the drives to teague platinums,props,fuel mods, oil system mods,prochargers etc. When they were done they showed teagues bill for doing it all,it was 52,000$. Boat went 18 or 22 mph faster and looked to be pretty reliable. Now 8000$ of that was there labor and I'm sure there was another 4 or 5 thousand in markup BUT still the same when it was all said and done it still ended up costing a small fortune,Smitty

Save your drives and stay with naturally aspirated engines and put the money in things like your drive/prop set-up....like checking for any hook in the last 3 feet of your hull or possibly some IMCO-2" shorties, etc. These are things that help you go faster and yet you will not neccesarily see an increase in fuel usage.

A friend of mine has the exact same boat as I do---32' Active Thunder. My 565cid engines only make a very conservative 615hp @5400rpm. My friend's 32' AT with 556cid SUPERCHARGED engines supposedly make 815+hp @5600rpm---a 400hp difference in his favor and yet I do the same top end speed as he does! Even jamming the throttles at 3500rpm he cannot pull away from me. He should be whipping my arss!-----but I think it is only because of the arrangement of equipment I have hanging off my transom....extension boxes, IMCO -2" shorties, 5-bladed props. Either way, you are going to have to lay down the $SMACK$, but at least it will save your drives.

hey kaama what do you have done to your motors as well as your drive train. i too have a 32 thunder with 500 hps and want to repower this winter. i would like to make 600 hp as well. pm me if you want

thanks rick

Sad to say but if you run all the numbers 10k will not buy the HP you need to get another 5 to 10 mph. Take the wife on a holiday and enjoy what you got . :ernaehrung004:

Rick, I have Stellings extension boxes, IMCO -2" shorties and P5X 5-bladed props. I knew your boat since Joe owned it---and I really like your boat. You can get 600hp from those 502's you now have, but you'll need good heads and cam combo. I'd be happy to talk to you, but I would also advise speaking with RMBuilder/Bob Madara of Marine Kinetics in N.Y. Do you have a reputable engine builder?

Just make sure you do your due dilligence when it comes to hiring a machine shop for building marine engines and make darn sure they have a very good reputation when it comes to building marine offshore engines. If you have the slightest doubt, then do not talk yourself into taking your engines there like I once did with a particular shop---I didn't listen to my own gut feeling. Ask around and ask lots of questions. I have over 200 hours/4 seasons on my engines since they were last built in May of 2005.

Not sure my PM is working, but you're welcome to PM or email me.