2GMF sheared bolt.

[Jim McCue]

I recently backed out, not the pivot but the tension setting adjustment bolt on the 2GMF (Not the 2GMF20) raw water pump (just left of the main pulley). The process was rather "squeaky"Oddly, I found that the long set bolt was kinda rusty and wet.Can't figure how it got wet- I've no leaks that I know of.Further inspection of the bolt seems to indicate that perhaps a portion of the threaded shaft has sheared of and I can't tell how much is still left reccessed in that receptacle. What's worse, I can't imagine how I might be able to reverse tap out the residual in the receptacle when it is that far reccessed (4-5 inches). The bolt"shaft" that I pulled out is 4.75inches long and 5 inches overall long- including the bolt head. I 'd appreciate if anyone could tell me the appropriate length of the bolt. And if I am sheared amid the threading (I still have 1 inch of threading on the bolt), how would I go about "tapping out" the residual bolt shaft without possibly boring into crooked into the threaded housing.I consulted Mack Boring but they didn't know- the bolt is not detailed on the diagrams! My luck ;{Thanks in advance. Jim McCue

 

[Sam Lust]

Not Likely

I really doubt you've sheared off the bolt. They usually break where the thread meets the plain shaft. Inspect the thread very carefully and you should see exactly where the male and female threads mated. Even better, buy a new bolt to compare to yours. (I can't believe the guy a Mack Boring wouldn't check the length for you. I think it's even stated in the parts manual!) If bottoming is a real concern put a washer under the bolt head before you pit it back in. Most important, smear Never-Seize on the threads before re-assembly to eliminate the chance of problems later on. I did ALL of the bolts that hold accessories on my 3GM30F before I set the engine in place. Great peace of mind!

 

[Jim McCue]

I wish

I was surprised that Mack boring could tell me about the bolt,... went there in person! Also they had no bolts in stock - said to go to Home Depot -yeah, for a metric bolt. But it didn't answer the question, how long is it. Thanks for the advice.I'm gonna put a probe into the opening and take a depth measurement and put a washer or 2 on it. Hopefully there's enough threading available to tighten the adjusting braket on the raw water pump. I sometimes sail into the northern part of Barnegat Bay. -Lemme know if you see me S/V "SafeHarbor". That is if I get this engine and alternator up and running sometime soon.Jim

 

[Dave McIlveen]

2GM Bolt

Better late than never! Jim I replaced that bolt on my 28.5 last year. 4.75" sounds just about right. Note that the pivot bolt and the adjusting bolt are identical. You could confirm this by pulling the other bolt.I ordered one from a local Yanmar dealer here in Atlantic Canada.Hope this helps.Dave McIlveen28.5 Osprey