Engine tick at 2000 rpm

[Anova1]

Hello. I have a 1979 cobra jet boat with a 403 Oldsmobile big block in it. Boat runs fine until it hits 2000 rpm then a ticking or knocking sound starts. New to boating and stumped on what it could be. I have a video but it won’t let me post it to this thread. Any ideas of what it could be would be much appreciated

 

[Canuckjetboater]

Hello. I have a 1979 cobra jet boat with a 403 Oldsmobile big block in it. Boat runs fine until it hits 2000 rpm then a ticking or knocking sound starts. New to boating and stumped on what it could be. I have a video but it won’t let me post it to this thread. Any ideas of what it could be would be much appreciated

@Anova1 ..... failing hydraulic lifter? valve stem seals leaking down?

 

[tdonoughue]

When it starts the knocking, does it get faster/louder as you get beyond 2k rpm or does it settle down and go away?

If you put it on a hose, does it still do it? Or does it only do it under load?

 

[Anova1]

When it starts the knocking, does it get faster/louder as you get beyond 2k rpm or does it settle down and go away?

If you put it on a hose, does it still do it? Or does it only do it under load?

It gets louder and faster. Not too much faster though. Will let you know if it makes noise attached to a hose.

 

[jdkaeser]

I would get a mechanic's stethoscope and put it all over until you find where the noise is coming from. Could be many things, an accessory driven by the belt, water pump, bad lifter, loose rocker, bent push rod. If it is a knock and not a tick, start with new plugs and checking the ignition system for loose items, plug wires, cap and rotor.

 

[Dwrat]

Could be loose exhaust bolts????