Stuck Wrist Pin (Pictures)

[Sureshot]

Working on a rebuild of a 50 HP 2-stroke Johnson that started here:

http://forums.iboats.com/showthread.php?t=520643

Thanks to all who helped me diagnose my issue. So the powerhead has been disassembled and the engine block bored. I got 2 replacement pistons but I'm having some issues getting the wrist pin out of the old scored #2 piston. The clips have been removed but the wrist pin won't slide out. I've put a few whacks on it with a deep socket / rubber mallet combo but nothing gives. The old #1 piston's wrist pin seems to slide out just fine. Any tips on getting a stuck wrist pin out? I'm trying to re-use the needle bearings and washers and of course don't want to damage the rod. Any help would be great.

 

[kenmyfam]

Re: Stuck Wrist Pin (Pictures)

Working on a rebuild of a 50 HP 2-stroke Johnson that started here:

http://forums.iboats.com/showthread.php?t=520643

Thanks to all who helped me diagnose my issue. So the powerhead has been disassembled and the engine block bored. I got 2 replacement pistons but I'm having some issues getting the wrist pin out of the old scored #2 piston. The clips have been removed but the wrist pin won't slide out. I've put a few whacks on it with a deep socket / rubber mallet combo but nothing gives. The old #1 piston's wrist pin seems to slide out just fine. Any tips on getting a stuck wrist pin out? I'm trying to re-use the needle bearings and washers and of course don't want to damage the rod. Any help would be great.

View attachment 126703View attachment 126704

Personal opinion only here.
If it's stuck then it has issues and nothing should be re-used. Especially as you have taken the time and the trouble to re-build and rebore. I would not re use any of the old parts in there. I know it's a little more expense on the re-build but for the peace of mind and the fact that if anything you put back in is not in A-1 condition you could end up doing the whole thing again. This goes for the "apparently good #1 cylinder as well"
As said though this is just my personal opinion.
Good Luck with it.

 

[dehydrated]

Re: Stuck Wrist Pin (Pictures)

use the other wrist pin as a guide and use real hammer personally i wouldnt reuse those needle bearings they are cheep and heat kills

 

[F_R]

Re: Stuck Wrist Pin (Pictures)

Whoa there!! More than likely it is SUPPOSED to be "stuck". You don't say what year your 50 is, but almost all OMC motors have wrist pins that are slip fit in one side and press fit in the other side. That allows the piston to expand and contract without distortion. So let's assume yours is also.

Look inside the piston. See if there isn't an "L" cast on one of the pin bosses. If not an "L" at least some sort of marking to indicate the slip fit (loose) end.

To remove or install the pin, the piston must be supported on the TIGHT side and the pin pressed in/out from above. In other words, the pin will be pressed all the way out through the tight side. To istall, the pin is slipped into the L side and pressed into the SUPPORTED tight side. Of course the old piston is junk anyway, but if you press the pin in the wrong side you will distort and destroy your new piston too. Manual shows a hammer, but a press is the preferred way. A bit of heat will expand the aluminum enough to make it slide through the tight bore easier. When it cools, it will be tight. (Or "stuck" as you say.

 

[Sureshot]

Re: Stuck Wrist Pin (Pictures)

Thanks everyone. Yeah I'll probably look into just getting some new bearings but I'll still need to get the pin out so I can re-use the rod. It's a Johnson 2000. I have the official OMC manual and there are no instructions about "loose" versus "tight" side in the piston assembly section. So I'm assuming the wrist pin can come out either side once the clips are removed. Comparing it to the other piston that came out of the engine, I can move that wrist pin fine. Not sure if the damage to the piston caused the pin to get tighter than normal.

 

[jbjennings]

Re: Stuck Wrist Pin (Pictures)

So do like F_R said and heat the bad piston up. Then get your wrist pin out. It should come out pretty easily when you heat that piston up. Try to give the piston the heat and not the pin as much as possible.

 

[Sureshot]

Re: Stuck Wrist Pin (Pictures)

A combination of heat and hammering did the trick. Wrist pin finally slid out and the rod is free. Thanks all.

 

[1946Zephyr]

Re: Stuck Wrist Pin (Pictures)

Yes, I am totally with F_R on this on. When you remove the wrist pins, always put the loose (L) side up. When you re-assemble it, remove the wrist pin completely then drop it back it from the loose side and press it back together with the loose side up. Doing so, will prevent eggshaping the piston.

For smaller pistons, I have a big rubber block with a hole bored in it, for the wrist pin to slip through. Ideally, you want to set the piston in a block, with it cut out the same size as the piston to basically cradle the piston. Always loose side up.