Wondering if anyone has any ideas. I just bought a 94 cat with a blown 468. The boat ran 20 mph slower than the indicated top speed. Also started to sound horrible we were towed back in, and found oil had spewed into the bilge,1 cylinder had 0 compression it dropped a valve, another had a flat lobe on the cam and a broken pushrod. Pulled motor and drive and sent out for a rebuild. I had another blown 454 that ran 104 2 weeks earlier in a similar boat so I put it in this boat along with the matching outdrive and prop The boat idled great and came out of the hole great but could only muster 87. Brought it down to idle started to run again and could not get any rpm's. idled back into harbor and came home.The first thing I noticed was the electrode on the plug was bent and #2 cylinder has 25 lbs compression. The only thing the same is the headers CMI elbow top with silent choice. I didn't have the compressor hooked up so they were completly open. Any Ideas?

Only thing same is headers? How about fuel, or fuel system. When motor runs out of fuel it only means you will be spending more money.

I would say you fried you second engine also. Detonation will do all kinds of things to your motor. My guess is you have some valve problems now if you are lucky that will be all.

Fuel system was replaced but I added to existing fuel in boat. That could be the problem bad fuel. Thanks

Leaking headers? Stuck partially closed silent choice? Spark plug wires?

Pressure checked headers they are OK The cylinders on the silent choice have a lot of resistance. I don't think it would have blown shut. I'm leaning toward bad fuel and then Water reversion with the silent choice and the cam I have. It will come apart this weekend and I will post findings.

My thoughts......

Not enough fuel, low octane fuel

What was oil pressure? Maybe a lubrication problem or high oil temp?

How many lbs of boost?

What is timing set at?


How old are both motors. If you bought them used there might have been a pre-existing problem.

Do you know what the fuel pressure at the motor was in both instances? I'm guessing that both motors had their own fuel pumps, in which case there may be a restriction in the pickup of sorts, or there may be a pump issue if it is common to the boat.

Check the fuel fittings from the tank as well. You should have 1/2 lines -10 from the tank to the pump with no anti siphon valve. Good Luck

Looks like bad fuel caused the problem #2 piston looks like it's been sandblasted with bb's. Expensive lesson. Oh well I wanted to build a bigger motor and it is winter,and it's a better reason to tell my wife why it needs to be rebuilt. Thanks for all the help

whats your water pressure?