Bolt turns up in bilge

[chopperdog]

Hi,

1988 OMC Cobra with 3.0L.
Engine used to have a very faint, weird vibration sound at 2200rpm. Now it's gone.
Bilge is spotless.

Now I find a 4" long 1/4" bolt that is snapped at the threads. It is just lying in the bilge, against the transom.
Unique Identification is that it has diamond shaped "grip" marks above the threads for about 1". It has a "D" on top.
It is not stainless.
It is a standard bolt, which a socket would be used on.
Out of the 4" length, only about 1/2" is threaded.

I obviously think the bolt was causing the vibration noise.

Any idea where the bolt could have come from?
There are no obviously missing bolts.

Could be related: There is a small trickle of water from transom through the plate a few inches above the drain plug. This was there before I found the bolt.

Could this bolt have been used to secure the transom plate, and it was broken, and therefore leaking?

Thanks,

Chopperdog

 

[a70eliminator]

Re: Bolt turns up in bilge

The transom plate uses a threaded stud with a nut on the motor side and it's much larger than 1/4", if you take a mirror and take a look you should be able to see the two lower mounting nuts.

 

[futz]

Re: Bolt turns up in bilge

check your starter bolts.

 

[Don S]

Re: Bolt turns up in bilge

Now I find a 4" long 1/4" bolt that is snapped at the threads. It is just lying in the bilge, against the transom.
Unique Identification is that it has diamond shaped "grip" marks above the threads for about 1". It has a "D" on top.

Yep, that's a starter bolt.

As far as the leak goes, pull the drive and check for water in the bellows. Could also be the cause of your noise and vibration.

 

[chopperdog]

Re: Bolt turns up in bilge

Thank you everyone.

I will check the starter tomorrow.
I have never pulled the drive before.
I understand I can build a rack to support it out of wood.
I will research the manual.

Thanks again,

Chopperdog

 

[chopperdog]

Re: Bolt turns up in bilge

You guys are definately correct.
I haven't had a chance to look at the boat, but I looked up starter bolts.
The bolt in question is definately a starter bolt.
Thanks for getting me going the right direction.

Chopperdog