a 4.25 rotating assembly is $2000. It’s not another 25,000 to build 540s especially on older engines. Everything’s gonna get replaced anyway other that’s if crank and rods are good

For me, it would depend on the condition of the crank and rods. If they are fine, I would over bore as needed and upgrade the cams and valve train. I would also ditch the cool fuel and go with an electric pump, regulator, and return line to the tank.

You dont build a 540 out of stock 502 crank, rods and pistons............the machine work alone would probably be 5k for the pair, new 6.385 rods, 4.50 pistons, 4.25 forged crank, new heads a minimum of 5k.....and the heads and stock intake is not designed for the bigger cu in so add that in also

25 years 1600hrs and no issues.
Im doing this $hit all wrong!!!

I understand the process Frank McComas made my 502 540s. I’m only saying that if you keep it 502 you’re still buying pistons and rings , reconditioning the stock rods and buying rod bolts , and polishing / turning crank. The only machine that would need to be added would be slight clearancig for the longer stroke. It’s going to get decked and bored either way.

And I left out cams, lifters, rockers.....................I say build the 540's if you have the cash

Last fall, I left my VR 1 Velocity with Jason and Johnny Saris. They turned my 502 into a 540 which dynoed at 641 hp. Sounds great and runs even better. The midrange power is unbelievable! I am by no means wealthy but I dont regret a dollar of what it cost.

Padraig

Is 5-8 mph worth loosing a month or more in the summer with mechanical breakdowns?

Cost of the rotating assembly is one but are you going to use the 502 mag intake?.......no way it allows enough airflow to take advantage of the cubic inches.
If you upgrade the intake/plenum, will your exhaust now allow for that extra air to get out?
If you increase torque by 100-150 pts, do you really think your drives are going to last multiple summers?

I'm all for "cheap HP" but the reality is all these things work together. If you don't do them all then you really aren't doing much.

FWIW: With a Formula 382 many years ago I turned a pair of 500EFIs into 10:1 compression 540's. LOTS of plenum work, head work, cams, exhaust. Ran/sounded great but even with XRs I trashed a drive every 18 months after that. Don't regret it but it was quite expensive.

IMO It all depends on how you like or want to boat. You got 1,600hrs pretty much trouble free. If you were happy. I’d stay that route. You might run 10mph’ish more with the 540’s. And will be fun for a while. But, depending on the build, you won’t get as many trouble free hours in my opinion. If you don’t mind some headache weekends. Go with the 540’s. If you like to go to lake and turn key and boat every weekend trouble free. Stay with stock 502’s.

thats before merc started charging gold bars for xr gears and duffel bag full of hundo's for a complete xr drive.