XJ99
Seaman Apprentice
- Joined
- Feb 18, 2013
- Messages
- 44
- Engine make/model - Mercruiser 4.3 V6 (EFI)
- Is it a new problem and previously engine was running fine - Just bought the boat
- Engine hours(if you don't know, make a good guess) 211.6 hours
- To the best of your ability best describe the problem:
starts right up no problem. When running around 4k RPMs it sounds just fine,
no power problems, gets right up on plane. When I push it past 4K I get a very
random knock sound coming from the stern area. It only does it under a load.
In neutral, I can rev it up with no issues. It does it on a calm lake no waves, doesn't
matter if I turn or just keep it straight. The knock isn't constant, or predictable at all.
A friend thinks it's old ethanol gas in the boat. I added some marine stable that didn't help.
Any other info I need to provide, just ask... Thanks for any help.... Gino