These threads have been done in the past - technology has changed and frankly prices have come down on some components. Can it be done without the AFR and without stroking the motor and changing all the internals?

Got a pair of bone stock FWC carbed 330HP Mercruisers and looking to do a BUDGET upgrade. Good compression in all cylinders, 4-bolt main, nothing special, no oil burn. Gill exhausts with a 2-foot drop to throughulls which are 4-feet rear of motors.

Performance goal is to get as much torque as possible and 450-plus HP on 91-octane pump gas (non ethonol stuff at marinas in FL) - RPMs should be sub 6,000

Heavy cruiser NOT a poker-run boat....42-feet, 10-foot beam, 10,000 pounds deep vee.

What "bolt-on" recipe would you use?

Can we bump compression a bit with heads? Which ones?

What intakes?

What CAM?

What carb?

If budget allows I might go Ftech EFI instead of carb.

Look forward to suggestions.

How about we call it a formula? We are not baking cookies. Sorry, the term recipe irritates me, sorry BBlades...you are not baking cookies either.

My opinion...before sinking a bunch of cash in a 330 sell your boat and buy one with the higher power.

The 330 internals are cast and the weak link. Best off to start from scratch with some 502's or 540's.

If your gonna do something on a budget, over due it. This way you only pay for it once. Most people say I have to do it on the budget and save a couple hundred here and a couple hundred there. When you do this you cost yourself more money. It breaks because the crank can't hold the power and the rods are cheap. I built a 500hp 580tq 454. It's stroked to the 496 and the forged crank is good for well over that. Make the motors strong so you don't have to play the rebuilding game because the bottom end ate sh**.

Here is what is going to help you. the 454 and the 502 use the same size crank and rods. The difference is the 33 454 is a cast crank with little rods while the 454 mag and 502 are forged cranks and stronger rods.

If your diligent and look you can find a used 502 crank and rods from somebody building a stroker motor. The down side is that if the peices need work your not saving money. A forged rotating assembly to make a 454 or 496 can be had for under 2k.. If your lucky you have a gen 6 block which is a 4 bolt and roller.. find a decent 500 efi take out cam, some eddie alum heads (not the best heads but thdecent and alum so you can get a little more compression, 2500...used stainles marine ex. 900.... machine work etc, 2k so your budget 500hp motor is now at least 7000...

I saw a used hp500 for 4k the other day....

I wouldn't worry so much about the cast internals staying under 500 hp however you'd be hard pressed to get that given the situation. Perhaps set your goals to 420 or save yourself some money and purchase a set of fresh or recent rebuilds for sale on swap shop.

There are a set of 174 blowers in the swap shop for $ 2,300. Bolt them on and go. Not the optimal match of parts but no motor pulling and parts buying. I bet you could get close to your goals with just this.
P.s. I am NOT a smart guy!

I think the cast cranks would be OK in a cruiser that is not likely to see extremely high RPM's and wave launches like a smaller boat would see. I would maybe spend some time to upgrade to some better aftermarket rods, or find a set of good take-out 7/16" bolt rods from a 454 or 502 mag. Barring that, at least upgrade the rod bolts to some good ARP's. To make you sleep better, you could also add a set of main studs. I don't know if I would gamble too much with trying to run a completely stock 330 bottom end with power upgrades to the 500 HP range. The cast pistons might end up being the biggest issue, unless you have the tune completely dialed in.

Merc made a 454-based HP450 that essentially used the same cam, heads, carb, intake and exhaust as the 500HP (502 based). You could probably find a lot of these parts in Swap Shop.

Saw some threads on here discussing some decent aftermarket cast iron heads that might be a good alternative to the GM rectangle port heads. I would recommend upgrading to a set of the good Ferrea SuperAlloy exhaust valves for insurance. JayRacing.com site had them for around $400 a couple of years ago. Also, don't cut corners on valvetrain components, especially if going to a healthy roller in the .600 lift range. Hard to go wrong with the Isky Tool Room springs.

FWIW, a fellow OSOer did a major power upgrade in his single engine Formula performance cruiser. He saw some gains, but not quite to the level that he expected. I wouldn't expect a big heavy boat like a cruiser with an inefficient hull design to respond that much to a relatively modest power increase.

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