And SD if you are refering to my comment I in no way said they are junk, read my post again!!

do u have any ideas of why it would be running hot after driving it hard. it doesn't do it after driving at cruising speed

I would suspect a scored impeller housing or a small blockage somewhere in the cooling system.

I read your post. Reading comprehension is not something I have much trouble with.

I was not talking about you and I don't believe I even mentioned your name.

My opinion is probably not that closely monitored around here anyway so no need to throw the defense at me.

I do have a habit of getting involved in 496 topics only because it's something that I've pretty well figured through a lot of time and money.

I honestly don't care if you like or hate them. I just didn't want the guy to feel like he owned a total pile cause it broke.

A 500 EFI isn't the best answer either if you live in salt 24/7.

There, there....

Who said they were junk all of a sudden????

You can bore it .010 over or .060 over and get Wiesco pistons from Summit or get a crank, pistons and conn rods from Raylar. $1400 plus machining for $200-400. Re-assemble and your done. Or add the Raylar heads and/or more. Since your engine is toast, it has no resale value. You can buy a 525 or 500 but you are out big cash. Rebuild the 496 with Raylar - he has a great forged package and you can be up and running with a lot more HP for under $10K or stock HP for $3000 (if you do the re-assemble)

I've done the math 100 times and I am 80% thru a 496 rebuild - If your engines are low hour you can sell them but for a high hour motor or one that is blown up, the rebuild is much cheaper

Keith you are right about the blown engine, it is only worth making it into a bar stool with no resale value.

The reason for the high temperatures is that the cooling system is compromised somewhere and can no longer handle the engine heat build up especially from hard running. Reduced flow of sea water or the engine coolant do to blockage or bad pump or sucking air or ....
Common cause of blockage in the sea water plumbing is do to rubber peices from a damaged pump impeller if that has ever happened to your engine. Check the coolant thermostat....coolant level. Check for pinched sea water intake hose at the drive or anywhere else. I am assuming that the engine coolant system is not choked with corrosion from worn out coolant. I have heard that the remote sea water dump drain valves and check valves can cause cooling problems as well. I think you get the picture.

Thanks for that, thats the sort of information I was hoping for.
I'm a marine engineer so it's gonna be a self build. Budget is tight but I wanna do this to last so its worth spending a little extra.
Are Raylar sometimes a little difficult to get hold of? I've sent a couple of messages but no responce.

Thanks again
Si