97 challenger vibration

[diamondauto]

Hi, I hope you guys can help me. I recently purchased a used 97 challenger with a single 787. I have had several problems that I have solved by reading this forum. Here is the latest, we were out on the water running at almost full speed when it stared to vibrate the whole boat. I slowed down and the boat died. It started up and the vibration was shaking the whole boat really bad. I idled back to shore and loaded the boat on the trailer and took it home. I checked for something in the impellor area and found nothing. I remove the pump and drive shaft, the shaft is not bent and the pump looks good, the impellor has been repaired or rebuilt by the previous owner and spins freely with little or no endplay, the bearings feel good with no roughness. Some of the problems Ive had with this boat was one for the rave valves went bad so I replaced it. It was also getting too much water in the engine compartment, a combination of no scupper valve and the last owner replace the sump pump and put it in the wrong location, it has an aftermarket airbox which caused the water to get injested fouling out one cylinder. I have replaced the scupper and sump pump so Im not getting water in the engine any more. My problem is the vibration, it happened after fixing the other stuff. Any suggestions, advise or ???? Im stumped. Thanks Craig

 

[phough5757]

Things I would try.

Remove the jet-pump. Start the Engine. I think the 787 has a balance shaft.
I think Your engine has jumped timing. Maybe pull the head and see if there
is any damage. May have just broke a spark plug.
Good luck!

 

[Dr Honda]

If you pull the pump... make sure you pull the driveshaft before you start the engine. Otherwise, the driveshaft will whip around and break something.

 

[diamondauto]

Thanks for your suggestions, I had already removed the pump and driveshaft so I checked the sparkplugs and started the motor. It was the counterbalance shaft. Unfortunately when I started the motor and started to rev it the balance shaft came apart and took out the side of the engine. Looks like I will be replacing the engine, if you have any advice on engine replacement I'll take it.