"I have been having trouble wi
"I have been having trouble with a mysterious noise coming from my enigne - similar to another post here - but I want to include more info in the hopes that someone else has had the same problem. A couple of marine mechanics are scratching their heads over this one!
I have a 1981 Hourston Glascraft with a Mrecruiser 470. I assume original engine the same vintage. About a year ago, the engine started making an intermittent sound at rpm's above 3200. The sound, to me, as like a knife edge or chisel being lightly touched to a grindstone - a tinny, mettalic "zzzzZZZTTT" sound that would appear for a second or two then disappear. Sometimes there would be a short interval in between sounds (7-8 seconds), sometimes minutes, and sometimes I would not hear the sound for an hour or more. In general, the sound would disappear if I throttled back to 3200 rpm, although recently when the boat was heavily loaded the sound appeared at 3000 rpms.
Took the boat into the shop and they checked everything external to the engine and could find nothing. First suspicion was a loose piece of magnet flying around in the stator, and the list went on from there. I suggested maybe flapper valve and was told that was new. Eventually the shop stated the problem had to be internal and that the engine needed rebuilding (it had been rebuilt only 380 hrs previously). So, the engine was rebuilt, and $6000+ later the sound is still there. Then the suspicion was faulty timing and the distributor checked and adjusted - no joy.
Does anyone have any ideas???"
"I have been having trouble with a mysterious noise coming from my enigne - similar to another post here - but I want to include more info in the hopes that someone else has had the same problem. A couple of marine mechanics are scratching their heads over this one!
I have a 1981 Hourston Glascraft with a Mrecruiser 470. I assume original engine the same vintage. About a year ago, the engine started making an intermittent sound at rpm's above 3200. The sound, to me, as like a knife edge or chisel being lightly touched to a grindstone - a tinny, mettalic "zzzzZZZTTT" sound that would appear for a second or two then disappear. Sometimes there would be a short interval in between sounds (7-8 seconds), sometimes minutes, and sometimes I would not hear the sound for an hour or more. In general, the sound would disappear if I throttled back to 3200 rpm, although recently when the boat was heavily loaded the sound appeared at 3000 rpms.
Took the boat into the shop and they checked everything external to the engine and could find nothing. First suspicion was a loose piece of magnet flying around in the stator, and the list went on from there. I suggested maybe flapper valve and was told that was new. Eventually the shop stated the problem had to be internal and that the engine needed rebuilding (it had been rebuilt only 380 hrs previously). So, the engine was rebuilt, and $6000+ later the sound is still there. Then the suspicion was faulty timing and the distributor checked and adjusted - no joy.
Does anyone have any ideas???"