Check rebuiltmaineegines.com or atk-engines.com (same co.). I just got quoted a vesuvio 468 w/ 450 hp and 500 ft/lb for $4395 for the long block and $5995 for the drop in. Just passin it along.

and BTW - I had a 242 LS and had a stock from GM 502/502 dropped in and had no problems through 200+ hours and ran 62 on GPS with a 23 Mirage Plus and 64 with a 25 Mirage.

The guy that bought it still is runnin strong 2 years later.

My buddy's had a Merc 502 MAG/415 hp and did 60/61 with a 23 Mirage and 62 with a labbed 24 Bravo. You sure that was a 502/502. His new 509/535HP gets him 69/70. A true 502 hp should get you near 67/68 mph ,I would imagine.

unless the aluminum heads were fake and the stickers on the valve covers were just kidding then yep, I think it was a zz502

Just thought I'd add my info to this thread. My 88 242 ran 63 with a ZZ502 and stock exhaust manifolds. With the addition of lightning headers I saw 68.7 both speeds on a GPS. With some more additions I've seen a best of 69.1 (demon 850), All speeds are with labbed 23 mirage props . Someday I'll find a good 4 blade to experiment with. That's after I get the new cam and intake setup figured out. I added a cam close to the 525 EFI cam along with a victor JR, but have an airgap to try also. All I know is the faster the boat goes, the better it rides. 65 is way better then low 60s.

My best so far has been 62.8 mph on gps. Mk IV bowtie block casting # 10051107. The PO told me it was a 502. It has the stock merc 454 intake, edelbrock 750 cfm carb, and what appears to be imco manifolds and risers although "imco" isnt on the castings. Outdrive is a bravo1 1.50 ratio spinning a mirage plus 23p prop at 5100 rpm.

we went 70 in an 89 242ls when testing for mercruiser it was a stock 502mag efi with a Blackhawk lol ... good day a lil less than half fuel and 2 light ppl itd touch 70.... good luck on finding a hawk though lol.

Probably a 500 up style build and a bravo with a shorty lower would get you there.

sell it and buy my 242 sr1 bolsters and twin 300 hp small blocks. runs 64...

Fischan 502's have 8.2 cast into them just below the deck surface on the side of the block if it's in the boat you will have to stand on your head and look past the exhaust manifolds. Lol. At least all the 502's we've run over the years do.

I'm pretty sure I'm the one that bought your boat, and it ran seven years trouble free. Has a new owner now.
Still miss it at times.