I have a Yamaha I/O 1990 4.3 V6 engine to which I did an engine overhaul. It did not worked when I bought it, so now is the first time when it comes to live in my hands...
While doing this, I had to pull out the transom, everything looked OK, just lubricate and put it back (after doing the alignment, of course...).
After a year of work, I finally started the engine
, which is working good.
BTW, I did an adaption to Mercruiser manifolds, as Yamaha are priced to heaven...
But back to transom... As soon as I fired the engine, I have heard a knocking noise coming from the back of the engine.
The noise is heard only at idle.. As soon as I rev up a bit (not much), the noise disappears.
I've read about noise from gimbal/transon area and most say it's the gimbal bearing or u joints...
To pinpoint the real culprit, I would need some other's experience with this.
I guess a worn-out gimbal bearing would make grinding noise, and continuously, not related to rotation speed.. Mine it's like knocking two metal pieces and definitely once per rotation... More likely are u-joints, but I need some feedback, for two reasons:
- Yamaha parts are very expensive and I do not want to order something that I would not need replaced.
- I cannot afford to keep the boat "open" until I find the culprit, then order the part and wait until comes...
Just want to stress that the knocking sound is the highest in low idle (say, 700 RPM) and fades away while rising the revs. It completely disappears a little over the idle speed (say 1100 RPM)... Over that speed, no noise at all....
The gear shifts well, but here I have another question> When putting into gear (forward or reverse), it makes a noise like when you put in gear a car without using the clutch. Is that normal?
Any advise will be much appreciated.
While doing this, I had to pull out the transom, everything looked OK, just lubricate and put it back (after doing the alignment, of course...).
After a year of work, I finally started the engine
, which is working good.BTW, I did an adaption to Mercruiser manifolds, as Yamaha are priced to heaven...
But back to transom... As soon as I fired the engine, I have heard a knocking noise coming from the back of the engine.
The noise is heard only at idle.. As soon as I rev up a bit (not much), the noise disappears.
I've read about noise from gimbal/transon area and most say it's the gimbal bearing or u joints...
To pinpoint the real culprit, I would need some other's experience with this.
I guess a worn-out gimbal bearing would make grinding noise, and continuously, not related to rotation speed.. Mine it's like knocking two metal pieces and definitely once per rotation... More likely are u-joints, but I need some feedback, for two reasons:
- Yamaha parts are very expensive and I do not want to order something that I would not need replaced.
- I cannot afford to keep the boat "open" until I find the culprit, then order the part and wait until comes...
Just want to stress that the knocking sound is the highest in low idle (say, 700 RPM) and fades away while rising the revs. It completely disappears a little over the idle speed (say 1100 RPM)... Over that speed, no noise at all....
The gear shifts well, but here I have another question> When putting into gear (forward or reverse), it makes a noise like when you put in gear a car without using the clutch. Is that normal?
Any advise will be much appreciated.
