So I found this bolt ...

[rpwillia]

in my engine bilge. It is a flat top socket bolt that is M10 x 1.25. It had to have come off the engine somewhere. Any ideas?

 

[jviss]

Scary. God only knows. One way to track it down would be, if you have the engine parts manual, is to search for that particular screw.

 

[shemandr]

Could you post a picture of the head of the bolt where there is some lettering? If you could put a dime next to it for those of us who don't know what M10 X 1.25 means. Maybe someone will pass a clue on.

 

[jviss]

what M10 X 1.25 means

M = metric
10 = 10mm diameter, about 3/8"
1.25 = 1.25mm thread pitch, or about 20 TPI

Note the inch comparisons I supplied are not correct, only the metric designation is; I just gave them for our metric-challenged associates.

 

[Rick486]

Perhaps not structural due to the counter sunk head. Looks like a bolt that would retain a part to a larger part, like the engine block. Look at things like the fuel filter, oil filter attachment, alternator, shutdown attachment, etc.

 

[rpwillia]

I just went through the entire M25XPG manual at https://www.westerbeke.com/parts manual/201021 parts manual m25xpb-m35b-m40b revision 2 final.pdf and I do not see that flat top socket bolt anywhere. There are plenty of M10 bolts, but they are either capscrews or regular bolts. At this point I am just going to have to get a mirror and look everywhere. A 6mm allen wrench fits it and it has the markings MSV and 10.9 on the head. FWIW I cheated and took it to Lowes and used their bolt finder to find the size.

 

[Tally Ho]

Probably thrown in there by a PO just to drive you crazy!

I have heard stories about Cadillac owners trying to find the source of an annoying rattle in the dash or door panel…just to find a nut with a tag on it, left there by someone on the assembly line on a Friday afternoon

Of course I did find a couple of nuts under my engine once, and then I noticed that 2 of the transmission output flange to prop shaft coupling bolts were missing the nuts !

good luck on the scavenger hunt

Greg

 

[rpwillia]

Probably thrown in there by a PO just to drive you crazy!

Thanks Greg you actually made me laugh. But I have owned the boat for 16 years now so this is a new one on me. It looks wicked familiar so when I fit its home I will likely be slapping my forehead as it will be obvious.

 

[Tally Ho]

Thanks Greg you actually made me laugh. But I have owned the boat for 16 years now so this is a new one on me. It looks wicked familiar so when I fit its home I will likely be slapping my forehead as it will be obvious.

Ok…so you are the only one to blame!

 

[JoeWhite]

I believe it holds the engine mount to the engine block.

 

[Crusty Ol Salt]

I would look for something painted grey.

Next I would inspect the steering and pedestal

 

[jssailem]

Guessing, it may be a set screw or cover hold screw to something.
Perhaps the starter motor cover.

 

[Benny17441]

People drop things and then figure it is not worth it to hunt them down and just leave them. If it were important , something would have busted by now.

 

[Serenity on Hudson]

The window on my new 1968 VW was making noise so I took the door apart and found a glass Heineken bottle sealed in the door. Friday manufacture?

 

[rpwillia]

Bazinga! Joe White gets the Gold Star. Turns out it is one of two under the bracket that the port motor mount attaches to. In the part manual they show those as Cap Screws but on my engine they are flat top socket bolts. Attached is a picture on the port side as well as the page of the engine manual (tried to get a picture of the port side, but the angle was bad and the light worse); part #18 is the one.