5.7 knoicking in gear at 2500 rpm.

[ltfella]

I have a 5.7 with alpha one 1989.I replaced the outdrive so its not that. When I out it in neutral and hogher rpms it runs great. Put it in gear can hear a knockin the back of the engine. I replaces the outdrive so I know its not that. When I have it on trailer it does not make the sound but when i Put it in water after 2500 rpms I can hear the knocking. any ideas?

 

[Bondo]

Ayuh,...... Welcome Aboard,..... Probably piston slap or a rod knock,....

Induce the knock, then remove the plug wires, one at a time to see if ya can make the knock go away,.....

 

[ltfella]

Hello Bondo. Ok I took the boat out today and made the noise go away with a plug wire. So what will that mean? If its a piston bearing will it hurt it if I keep the rpm down for the remainder of the season and if so as long as the shaft isnt shot I can replace the bearing only?. I only have about 12 hours on the engine.Hope for more advice. Dave

 

[Bondo]

I only have about 12 hours on the engine.

Ayuh,..... New motor,..?? Contact the builder,.... You've got a real problem, not something to ignore,....

Runnin' it,... it'll only get worse, til total failure occurs,...

 

[ltfella]

Ok so if its a bearing that can be replaced correct? Or do you think its something more?

 

[Bondo]

Ayuh,.... If it's a rod bearin' that can't be answered til it's torn down, inspected, 'n measured,...

If the crank is torn up, another motor might be necessary,....

Like I said, if it's a new motor, contact the builder, you've got a real Problem,....

 

[ltfella]

Well Its hard to get a hold of the builder when they wont talk to me so Im buying a new engine and see what I can do.