Preload Pin Frozen - 1988 Mercury 35 - 2 Cyl.

[rstier]

Hi,
I'm in the process of rebuliding my water pump on my 1988 Mercury 35 HP outboard. I noticed my driveshaft has a preload pin at the top and it appears to be frozen. Can someone explain what that pin does and am I right to assume that should move freely? If it is supposed to move, what issues would it cause if I can't free it up?
Thanks,
Ron

 

[hotrod53]

Re: Preload Pin Frozen - 1988 Mercury 35 - 2 Cyl.

I have a 1977 50 HP and my preload pin did not spring up and down either. I had the same concern that you are expressing, I'll be watching for responses but I beleive that it does not move.

 

[rstier]

Re: Preload Pin Frozen - 1988 Mercury 35 - 2 Cyl.

Not sure if yours is the same but my pin is supposed to move. Just saw a diagram of it and there is a spring underneath. Time to try
soaking it in PB Blaster overnight.

I have a 1977 50 HP and my preload pin did not spring up and down either. I had the same concern that you are expressing, I'll be watching for responses but I beleive that it does not move.

 

[Moody Blue]

Re: Preload Pin Frozen - 1988 Mercury 35 - 2 Cyl.

That pin puts a preload on the drive gears in the lower unit. It has a HIGH spring pressure on it and will "feel" like it is seized but most likely not. Take a hammer and tap it gently and see how it feels. If it is springy, it is fine.

 

[rstier]

Re: Preload Pin Frozen - 1988 Mercury 35 - 2 Cyl.

Thanks for the info. Mine was definitely frozen. I put some PB Blaster on it and let it sit for a bit. I then placed a wooden block on the pin and whacked it with a hammer a few times. That must have loosened it up because now it presses in and pops back out.

That pin puts a preload on the drive gears in the lower unit. It has a HIGH spring pressure on it and will "feel" like it is seized but most likely not. Take a hammer and tap it gently and see how it feels. If it is springy, it is fine.

 

[hotrod53]

Re: Preload Pin Frozen - 1988 Mercury 35 - 2 Cyl.

Huh.... interesting. Mine is together and ran for a year, I guess if it were stuck I wouldn't have been able to bolt it together. Maybe I just didn't press hard enough.

Thanks for the info!

 

[Moody Blue]

Re: Preload Pin Frozen - 1988 Mercury 35 - 2 Cyl.

Thanks for the info. Mine was definitely frozen. I put some PB Blaster on it and let it sit for a bit. I then placed a wooden block on the pin and whacked it with a hammer a few times. That must have loosened it up because now it presses in and pops back out.

The spring force is much too high for you to be able to press it in and have it pop back up. If it is that free, the spring is likely broken. You should not be able to move that pin by hand. Tapping it lightly with a hammer will compress the pin very little and will rebound firmly.