Mercury bb 850, shift shaft came out of lower unit

[crazymac-680]

Hi guys
I'm hoping you can help me. I've spent all afternoon reading and not managed to find anyone with the same problem as me. While changing my waterpump everthing went smootly. However I realised it was stuck in forward. I have now realised that my shift shaft should not have come out of the lower unit and now with the lower unit off I cant get the gears to change. The shift shaft just seems to spin.
When I push the shift shaft as deep as it goes. It spins by hand easily but not changing gear. When I pull it out about a cm, it turns with resistance but it's not coming out of forward.
I've tried spinning the prop while turning the shift shaft without feeling any difference
Does anyone have any ideas? I really dont want to have to strip the gearbox as I dont have the tools for that job.
Thanks in advance for any help

 

[latin monkey]

Re: Mercury bb 850, shift shaft came out of lower unit

the top of the shaft goes into the shift linkage at the powerhead. it probably slipped out. same thing happened to me not long ago

 

[latin monkey]

Re: Mercury bb 850, shift shaft came out of lower unit

just read your post again and misunderstood. if the rod came out of the lower unit then i cant really help you there except maybe to keep trying to work it back in

 

[crazymac-680]

Re: Mercury bb 850, shift shaft came out of lower unit

just read your post again and misunderstood. if the rod came out of the lower unit then i cant really help you there except maybe to keep trying to work it back in

Thanks anyway. I think I'm about to go out and give it another try. I found a picture of a shift cam and maybe it's just a bit still to get it back in. I'll try a tap and move approach until I hopefully get some purchace on the shift cam.

 

[crazymac-680]

Re: Mercury bb 850, shift shaft came out of lower unit

Its really not coming out of forward. It really feels like it's at the bottom and it just seems to be spinning freely by hand. About a cm from the bottom it reaches a keyed area. Then once in, it just spins freely again.
I have no idea why it's not changing gear?
It was fine before it pulled out.

 

[emckelvy]

Re: Mercury bb 850, shift shaft came out of lower unit

There is constant pressure on the shift cam, via the shift plunger and spring-loaded shift clutch.

When the shift shaft pulled out of the gearcase, the plunger pushed the shift cam out-of-position. So when you stick the shaft back in the hole, it's just hitting the top of the cam (or bottoming out on the structure inside), instead of going back in the splines.

To fix this without disassembling the gearcase, you'll first need to drain out all the gear oil.

Then remove the shift shaft bushing/seal assembly so you can easily see down the hole where the shift shaft goes. The bushing has right-hand threads and just unscrews. You'll need the special tool to fit the slots in the bushing, or grind an old socket to fit.

Spray some carb cleaner down there to wash away any residual gear oil, be sure you keep the drain plug open to let the excess out.

Grab hold of the prop and turn it in the direction that it ratchets - clockwise.

Note that right before the next 'click', you'll feel a bit of resistance, then the 'click'. What's happening is, the beveled edges of the shift clutch are riding on the corresponding edges of Fwd gear. As you turn the prop, spring pressure forces the clutch against Fwd gear.

The click you hear is the shift dog suddenly moving from the top of one edge or 'ramp' on the fwd gear, to the bottom of the next.

As the clutch 'climbs' the ramps, it moves back slightly in the gearcase. This takes pressure off the shift plunger and will allow the shift cam to be 'jostled' back into position.

So, once you've got a feel for how the clicking works, turn the prop and stop just before the next click. When you feel that slight resistance.

Then, peer into the shift shaft hole with a strong lite. You may see the shift cam and the center splined hole looking at you.

If you don't see anything, give the gearcase a 'bump' to and fro, side-to-side, and you should see it come into view.

The goal is to get the splined hole in the shift cam centered so you can reinsert the shift shaft.

Soon as you get that hole lined up, get that shaft back in there!

You'll probably have to do this a few times 'til you get it just right. And the prop might come off the 'ramp'.

No Worries, Mate, just set it up and try again. The shift cam is pretty much captured in its little space. It can't do much more than move around a bit.

Note that you'll see a groove towards the top of the shift shaft; there's supposed to be a clip installed there. When the shaft pulled out, the clip was left behind. If you see the clip, use a magnet to get it out. If you can't see it, it's probably fallen inside the lower unit. In that case I'd definitely use a magnetic drain plug and likely that'll catch the clip.

You can go to an auto parts store and get a "C" clip which will hold much better than the factory spring clip. Just take the shift shaft with you to get the right fit.

Well, that's about it, HTH & G'luck.......ed

 

[crazymac-680]

Re: Mercury bb 850, shift shaft came out of lower unit

You are a legend! Thanks so much. I'll head out for a bit of a play

 

[crazymac-680]

Re: Mercury bb 850, shift shaft came out of lower unit

Had a go at getting that bushing out with a set of open pliers but its far to stiff. It will all have to wait until Monday now. I got a wedding tomorrow and working Saturday and Sunday night. I'll get the right tool to get the bushing out on Monday and try again. Hopefully I'll find some kind of attachment for my impact driver that will take it off.
Thanks again
Dan

 

[emckelvy]

Re: Mercury bb 850, shift shaft came out of lower unit

A little heat applied from a propane or MAPP torch will help. Heat the outside of the gearcase to either side. Don't set the impact too high as it'll likely strip the bushing.

G'luck.......ed

 

[crazymac-680]

Re: Mercury bb 850, shift shaft came out of lower unit

It's all back together and running again. Really chuffed all thanks to Emckelvy.
Thanks a lot
I searched high and low for the shift shaft bushing removal tool and needed the boat ready for the weekend so couldnt wait for it to come via postage. So I forked out for a grinder a vice and 4 x 23mm sockets. Thinking that there is no way I would manage to make this first time. However within 15min I had a good tight fitting socket that fitted my impact driver. Gave it a couple of firm taps and it loosened up. With the gearbox oil already out and bottom plug out. I poured in some clutch fluid so I could see what I was doing. I turned the prop in the clicking direction(clockwise) until just before the click to take the pressure off. I still wsnt exactly sure what I was looking for, so picked up the gearbox and had front of the gearbox pointing to the sky with the driveshaft horizontal. Gave it a shake and the cam slid into view. I held it there while a friend replaced the shaft. I then placed the bushing over the shaft and tighten it up with a couple of screwdrivers and a a few taps with the hammer. On my own now I set at putting the gearbox back on. For some reason I decided to put it back on in neutral but couldned get the driveshaft to line up. Lowered the driveshaft and the damm shift shaft came out again. This time I had it back in the gearbox in about 5 min on my own. Tried again with the gearbox and controls back in forward. This helps a lot since you can move the driveshaft to match the engine.
Little by little I'm getting braver. I think I might try a gearbox rebuild in the winter. Even with the gearbox off I cannot engage reverse. Not a big deal since I've been without reverse for 4 years
Thanks again
Dan

 

[bwhalerman]

Re: Mercury bb 850, shift shaft came out of lower unit

It's all back together and running again. Really chuffed all thanks to Emckelvy.
Thanks a lot
I searched high and low for the shift shaft bushing removal tool and needed the boat ready for the weekend so couldnt wait for it to come via postage. So I forked out for a grinder a vice and 4 x 23mm sockets. Thinking that there is no way I would manage to make this first time. However within 15min I had a good tight fitting socket that fitted my impact driver. Gave it a couple of firm taps and it loosened up. With the gearbox oil already out and bottom plug out. I poured in some clutch fluid so I could see what I was doing. I turned the prop in the clicking direction(clockwise) until just before the click to take the pressure off. I still wsnt exactly sure what I was looking for, so picked up the gearbox and had front of the gearbox pointing to the sky with the driveshaft horizontal. Gave it a shake and the cam slid into view. I held it there while a friend replaced the shaft. I then placed the bushing over the shaft and tighten it up with a couple of screwdrivers and a a few taps with the hammer. On my own now I set at putting the gearbox back on. For some reason I decided to put it back on in neutral but couldned get the driveshaft to line up. Lowered the driveshaft and the damm shift shaft came out again. This time I had it back in the gearbox in about 5 min on my own. Tried again with the gearbox and controls back in forward. This helps a lot since you can move the driveshaft to match the engine.
Little by little I'm getting braver. I think I might try a gearbox rebuild in the winter. Even with the gearbox off I cannot engage reverse. Not a big deal since I've been without reverse for 4 years
Thanks again
Dan

I have a 70hp 1988 and when i pulled the lower unit the shift shaft came out of the tube. When I look down the tube i see the cam fills the hole view, When turning the prop to the click and advancing as described I see a pin slightly retract. Am I supposed to move the cam back? Is so which direction? Thank you very much for any information you may have.

 

[GA_Boater]

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