I know that HP is not cheap and a "budget" anything in boating is an oxymoron but humor me: If you had two kids in college and were unable to spend a bunch and had the following motors that are proving to be unreliable due to a crappy build - what would be the best bang for the buck rebuild-wise to get me over 500hp?

420 HP according to builder who is unreliable
Holley 850
BB 502s roller
Crane CAMs -unknown what's in them
Mechanical fuel pump
Raw water cooling with flush kit and Gill exhausts

Application is a very heavy 42 foot Cigarette on steroids in the 16,000 lb range with anrneson drives. I only have about 3 inches above the holley carb and spark arrestor since motors are under the cockpit floor.

Go long block 540 and move stuff over? Get this one bored out? Sell and start over?

Appreciate your educated perspectives. Thanks

Unreliable in what way? that will help people decide what may be best bet.

Go Diesel.

HE SAID ON A "BUDGET"

I have had the unpleasurable experience of a rebuild. I have learned that BUDGET and BOATING are not synonomous with each other. I wish you the best of luck in your quest.

Thats just a big boat for that power.
BTW, whats your budget, cuz my rebuild was to cost 3000-4000.
By the time i added new heads, exhuast and dressing the engine, dyno and then having the boat rigged properly for it, i was 10k in the hole.

Those 42's were intended to be diesel cruisers, not performance boats. It would probably cost you $40K to get that thing over 60mph. You may be better off with a different boat.

time to show the kids some tuff love, "boys i have decided to spend your tuition on some super chargers, i suggest you find well paying summer jobs and contact wells fargo about some low interest student loans"

motors under the floor?

interested in seeng a pic of this boat...can you share any?

THAT IS FUNNY CHIT RM, BUT SAID OFTEN IN OUR HOUSE WHEN THE KIDS SAY THEY ARE TIRED OF DOING HOMEWORK AND THEY DON'T EVEN WANT TO GO TO SCHOOL. ONE IDEA FOR THE REBUILD THOUGH IS TO GO STRAIGHT TO SOME NEW MERCURY CRATE MOTORS AND SALVAGE HEADS, ETC THAT ARE STILL IN GOOD CONDITION. FRIEND JUST GOT THE 500HP 502 CRATES PUT BACK INTO HIS BOAT FOR AROUND 15K (FOR 2) INCLUDING LABOR. NICE TO HAVE A WARRANTY AND 1000HP. THIS OF COURSE IS ASSUMING SOME OF THE BOLT-ONS WON'T BE YOUR WEAK LINK. NICE PART ABOUT ANY REBUILD WITH A WARRANTY IS THAT IT WON'T HIT YOU FOR HUGE UNEXPECTED REPAIRS WHEN THINGS WERE NOT DONE RIGHT THE FIRST TIME. MY .02