Need Some Help Engine Guys
 

I have a 1992 454 mag that it's looking like I sucked in some water, and bent a few valves. I havnt torn anything apart, but the last time it happened, it had the same symptoms, so I can only assume right now until it gets torn down. So, my question is, what is causing this? A little background. End of last season, I was cruising around the lake, around 4500 rpm or so, and the engine started to run really rough. So, I brought the throttle back, and it stalled out and would not restart. Almost made a sound like a dead battery, really slow cranking, but there was plenty of juice. So, I took it to a local reputable marine shop, and he told me I sucked in some water, and bent a valve. So, I gave him the go ahead to repair the bent valve, and overhaul the cylinder heads and what not. So, that was end of last season. Since then I have around 5 hours on the engine, and it appears Im in the same position again. The mechanic told me everything should be good to go, but to happen again around 5 hours later? I guess I am at a loss as to why twice now in that time frame. Any ideas here? To make matters worse, the boat is up for sale:mad:

I forgot to mention the engine has an Edelbrock cam and intake, if that will add anything to the equation.

If it happened at idle I would say reversion. If it happened at speed I would say head gasket.

Did your service tech tell you where the water was coming from? Head gasket, intake gasket or any cracks? If the mateing surfaces of you parts, block to heads, intaketo heads, are not true they will continue to prematurely fail. When the motor comes apart check the torque of the hardware also for any assembly issues. I'm by no means an expert but that's what I've seen from injesting water into a motor. Hope this helps.

Thanks for the reply's guys. It did happen at speed, not at idle. From what I was told, the manifolds were pressure checked for leaks, and the heads were machined at the local engine shop, so I would assume they would have made sure they would fit flush with the block. I guess Im lost as to why it would happen again with less that 5 hours use after I just had it all done. Luckily last time there was no damage to the piston when the valve bent, but not so sure this time. Another question I have is, is the mechanic somewhat responsible for what happened less than 5 hours later? Since the last repair and this one, we didnt see eye to eye on another issue, and I have since switched mechanics. Do I have any recourse with the one that did the work?

The heads were machined but was the block decked? As far wa waranty goes most of them are a 30/30 type 30 feet 30 seconds. good luck it can't hert to confront him about this.

The block stayed in the boat as far as I know, so I doubt it was decked as you put it. Im not sure if it would need to come out for that or not, but I dont think it was. Thats what my take is on the recourse with the mechanic. Im going to talk to him anyway, and see what he has to say, but I wont hold my breathe. All I know is I spent 2500 to have the top of the motor rebuilt, and am not going to be happy if I have to dish out another 2500. Thanks for the input guys.

i would have to think it is something to do with a warped gasket surface. If it was at idel or coming off of plane i would say elbows are to low or bad flappers

Check the exhaust riser gasket.They do fail and when the fail it will suck in water.Do you know which cylinders had water in them?

What exhaust system do you have? If it is through the hub, a suction occures when a reved up engine comes to a sudden stop. Any water in the oil?