Connecting Rod Bolts for Yamama

[rbablitz]

I just rebuilt a 200HP Yamaha and was told the connecting rod bolts to the crankshaft should be replaced. I was informed that these bolts are one use only. Anybody know if this is true or have heard any horror stories?

[boats.net]

I always replace them when rebuilding a engine.

[Ken]

rbablitz,
Ok, rb, "ours in not the reason why, but to do or die!" - sure would be nice to know WHY those bolts are one-time-use only.
I've never rebuilt an outboard - but if I ever do, I would like to know why I need to replace connecting rod bolts. Maybe some knowledgeable metallurgist will step up to the plate and explain this to us.
Good luck,
Ken K

[Bobbyr]

I just rebuild my 225 yamaha with the help of a local respected mechanic and we did not change mine we replaced all pistons ,used all old rods and bolts except one new rod. This guy rebuilds lots of motors so I hope I'm not going to have problems..

[brewski]

Not sure about the outboards, but here in the Auto world, we use stretch bolts, or torque to yield bolts. One time use bolts. You could reuse them, but not recommended.

[Ken]

brewski - that's interesting - you mean the connecting rod bolts are actually torqued until they stretch? Does this help them self-lock? And after they are "stretched one time", they cannot be stretched again? Just curious,
Ken K

[rbablitz]

Yamaha manuel mentions nothing about replacing bolt which kind of pisses me off. I do remember learning about torque to yield bolts in aviation school and did not think Yamaha uses them. But looking at the Yamaha manuel torque sequence (torque , remove tension then re-torque sounds like a stretch bolt or torque to yeild. Not sure if I should break down the engine again, but it sounds like I should.

Ken -- to answer your question, torque to yeild bolts stretch and form a somewhat "hour glass" shape to lock the bolt and are one time useable; did not think this was the case with Yamaha, but the Yamaha manuel really sucks.

[Ken]

Thanks for the info, rb - sorry about your dilemma - yeah, I have found a lot of mistakes in my Yamaha manual also - for what you have to pay, you would think they would be a little more accurate. Yet, my trusted marine mechanic tells me it's the best one available for my Yamaha outboard.
Good luck,
Ken K

[Bobbyr]

brewski said he wasn't sure about outboards,so whats the verdict?.Thats all I need is something else to worry about since my mechanic didn't say anything about replacing them and we didn't.

[Ken]

rbablitz and Bobby,
Well, it has taken me a while to get in touch with my trusted marine mechanic - he's the one I go to when I think I'm in over my head. He's got about 20 years experience repairing all kinds of outboards - he is good.
My mechanic says he has always used the old connecting rod bolts on a power head re-build - and I asked him specifically about Yamaha. He said he just puts a little Loctite (blue label) on the threads and torques them using a 1/4 inch drive and "calibrated elbow" method - said he has never had a problem.
Hope this puts your mind at ease a little about using the old bolts .
Good luck [img]smile.gif[/img] ,
Ken K

[brewski]

Calibrated Elbow, thats a good one. Why not use 1 rat-ta-ta-tats, with his air gun?

[Ken]

brewski,
cute - I'm not recommending the "calibrated elbow" method - I personally prefer my torque wrench whenever the Yamaha manual calls for it - my point is that replacing old connecting rod bolts with new ones is evidently not as critical as one might think from reading the other posts - Ken K

[Bobbyr]

Thanks Ken, Thats what my mechnic did (used old ones) Maybe that will give me one less thing to worry about.

[colossus]

Specially on four stroke engines, never use the same con bolts.
You cant apply the right torque, they stretch from the first step (from my experience).