billf1973

Okay I have a issue with replacing the con-rod in my 3.5 K&B outboard. I have tried the original bone style and the new style. There is some slop in the bushings on both ends. Any suggestions? Or is there supposed to be some movement and not snug?

ob nut

My Feedback: (1)

What crank do you have? 12mm or 13mm? Believe the 12mm has a "L" stamped at the end while the 13mm has "13" stamped. Old eyes, can't quite tell on the pics what is stamped.

Ron Olson

My Feedback: (1)

Mark, it looks like a 13 on the counterweight. The pix are fuzzy but I could make that out.

ob nut

My Feedback: (1)

Thanks Ron, that is what I thought. Just couldn't quite make it out on the small pic. There should be slight movement of "side to side" on both the crank and piston. But if there's a lot of "up / down" play, then there's issues. Have you tried another crank or wrist pin?

Ron Olson

My Feedback: (1)

That ain't sloppy. I bought a new SS and the thing didn't have any bushings on the con-rod! It was no wonder that I could never get the thing to run right.

ob nut

My Feedback: (1)

But when you opened it up to investigate, it voided the warranty!

billf1973

Thanks for the info guys. I didn't try another crank or pin. Don't have any. I will see about the movement direction.

ob nut

My Feedback: (1)

If you need another crank / pin, let me know. Think I have a few extra pins and possible a crank. I'm in the process of selling off my K&B 3.5 motors / parts.

billf1973

ob nuts, thanks. I am still trying to figure it out. Not much time to look at it lately.

billf1973

Okay guys, here is what I found out. It was a 13mm crank. After trying to reassemble the engine,the piston would not go into the sleeve again. I think the sleeve and piston need replaced. When using force to put back together they were both compromised.

ob nut

My Feedback: (1)

Yea, force is not a good thing for these little motors. I'd have to check what is in my parts supply, but I may have a used or even a new p/s if you are interested. I'm slowly working away from K&B 3.5 motors.

moparbarn

How did you attempt to install the piston? I have never heard of a piston not going back a cylinder it came out of.......The cylinder is tapered, tighter at the top, piston goes in from the bottom.

Ron Olson

My Feedback: (1)

That's what I was wondering also. Put the piston in then slide the sleeve in, it's usually that easy. Trying to put the piston in with the sleeve installed presents a problem. You can't do that.

ob nut

My Feedback: (1)

That's how I have to install new P/S in my MAC's, CMB's, OS's..The same goes for the 11's, 13's and 7.5 redhead I have. Since K&B 3.5 has the front end removable, it's easy compared to the other motors. Just gotta be careful about how it's done.