Is the first post always a question?
OK, I have a '74 Tahiti with a Berkeley 12JC-A pump and a BBF. There is some sort of sound that is similar to a knock although it just doesn't really sound like a piston knock to me... I've had a few engines in the past with genuine knocks. And it's stronger when I hold a screwdriver against the flywheel housing than it is anywhere on the engine. You can feel it on everything though, so it's a solid clank of metal for certain.
We checked the timing (10 degrees at idle and it goes up to around 30 or more - the scale stops- at 3K rpm) that's good right? Added a bottle or race octane and new premium fuel as part of an anti knock attempt. Couldn't get race gas at the time. I didn't know about the whole disconnect a plug wire thing I read about recently and will check that next. But so far we don't think it's a knock... but of course, will continue to check that out.
So far, none of the fuel stuff has changed the sound. Nor did messing around with the timing.
The sound doesn't happen at idle and starts around 1K rpm. It sort of goes louder and softer as the rpm goes up. It's probably the loudest at around 2 to 2.5 K RPM. I also notice that after the boat is in the water running for about 15 minutes to 30 minutes it gets worse. Basically, we idle out to the fast water.... drive it around and try to hear where the sound is coming from and in that time it gets worse. But will still go away at idle.
So far I was leaning towards something in the Flywheel/u joint connection to the jet but wanted to get some ideas from someone who maybe had a similar problem.... you know... a lot of the problems we have are common. And I don't know much about jets (yet) and don't know if the jet itself can make this kind of sound.
Any help ideas are WAY appreciated!