Mercruiser 1 Sterndrive

[Mike S.]

I have a 1978 Sliverline with a 140hp, 181 cid 4 cyl.

I am the original owner. There is a noise comming from the sterndrive
only when the motor is in netrural. If you shift into forward or reeverse the noise goes away. The oil in the drive has been changed twice this year and I have not noticed any wrong in the oil. I have taken the boat to two differant mechanics and they don't see any thing. The upper bearings where checked and found to be ok. The noise
can only be detected when the boat is in the water. Because when on the trailer with muffs on the drive, there is too much engine niose.
The best discription of the noise is a whirring sound. the boat is operated in fresh water only, and the water pump in the drive was replaced last year.

thanks, in advance

[big worm]

have u replaced the gimbal bearing that the drive shaft goes threw, they wear out and make noise like that.

[MIKE a.]

MIKE,CHECK YOUR FLAPPER VALVE,ITS IN THE EXHAUST MANIFOLD BETWEEN THE TWO HEAVY PIECES OF RUBBER BEFORE THE OUTDRIVE.WHEN THE RUBBER WEARS OFF THE VALVE,IT MAKES A TICKING NOISE AND CAN SOUND LIKE ITS FROM THE OUTDRIVE.