Sounds like a fun engine for your 242. I used to have an '87 242 LS with 530 +/- hp and it would run 68 MPH gps. The 242 is a great riding boat for its size mainly due to its weight, because of this, it takes a ton of power to make them go fast. I ran a Mirage Plus prop that was 21 pitch at 6100 rpms,

I wonder what I'll actually get with 600hp. The previous owner claimed 78mph with 630hp. We shall see!

I'd say you should be close to 75 mph. Honestly I don't think I would want to go much faster that that in a 242.

At 63 mph mine felt like it was running out of hull and chine walked really bad. It might have improved with 280's rather than the small bennet tabs.

The previous owner had a 630hp in my boat and got 78mph. He flat out said it was a death trap. As soon as I bought the boat I replaced the transom as it was rotted. I also replaced the transom assembly as the one on the boat was super sloppy. The boat rides nice and straight at 60 mph. Lets hope it does well as speeds increase.

Keep us posted on progress !

Current status: Shortblock is complete. Heads are still out being rebuilt. Blower is good to go. I picked up a HP500 oil system.

The only unknown at this point: Fuel lines- I got a nice Earls -8an fuel line on the carb so I need to get the line from the pump to carb. I have never dealt with AN stuff before.

I am hoping to get it on the dyno in february.

Well its been a while since I have updated.

The build is as follows:

Stock forged crank. Reconditioned forged rods with ARP bolts. Melling HV oil pump. TRW 2399 pistons .060 over. The heads I got are stock HP500 Carb heads. They have Manley Severe Duty intakes with inconel exhaust valves. I used a crane 134561 cam with their matching triple springs. The Blower and carb is all stock 525sc stuff.

I have a few questions with my setup.

According to desktop dyno compression calculator, with .005-007 deck height, 17046 Fel Pros, and 2399 pistons my compression will be 9.25-9.33. I am not a machinist so my measuring was with a feeler gauge on top of the piston. Kinda crude I know. What should my timing curve look like with that compression?

What temperature thermostat should I use? I was thinking a 120 to help with the higher compression.

I will be using 91octane non-ethanol only. No exceptions!

What numbers are you using for compression? Is the block bore notched? Here are my numbers;

1.2 cc .005 deck
9.5cc head gasket
1.5cc ring
-13.8cc dome
121cc combustion chamber

956.3 cc swept

9.0:1

There is bore notching, but it is very small. You can hardly see it in the pics. Fel Pro lists that gasket at 9.7cc. I forgot about the ring cc. I was also assuming 088 HP500 heads were 118cc. I would prefer to be closer to your number Mr. Maine.