Engine Rattle at WOT - Found a Bolt

[Mike Orth]

This is a continuation from my previous post on this problem. The original string is currently near the bottom of the first page of threads if you want to see the history....



Bob B. and members,



I was able to run around the lake this morning with the cowling off and did not hear anything other than a well tuned 125!! However, I did find the source of the rattle. A bolt in laying loose in the base/pan of the power head.



This could be a bolt that got dropped prior to me owning it (I have owned it for 1-year), or could it be something that vibrated loose? I can not find an open threaded hole that seems to be its home.



The bolt in question is photoed below. It is either and 8mm or 5/16 - 1 1/4 inch. Tried to get the thread, but do not have a gauge. I know that it did not thread on to a 10-24 nut...



Any ideas on where this may be from? Hoping Bob B. has a resource to ID this bolt size and it possible uses on my engine.



1996 Merc/Tracker 125

Serial #OG387689



Mike

 

[Mini]

Possibly holding the two halves of the lower cowling together.

 

[firedog978]

Years ago, I had an old Mariner outboard that would vibrate bolts loose seemingly on every outing. The first time it happened, the bolt was wedged in the shift linkage and prevented me from getting into reverse. I used lock-tite when I'd find one but, I learned to check under the cowling after each trip out. That thing turned into a pre-trip, post/trip check off.