Mercruiser drive grinds into reverse, fine in forward

[adam_man]

Hello all, I've spend a LOT of time looking all over the web for some help on this issue but nothing seems to be exactly the problem I'm having.
So heres the problem:

Its a pre-alpha drive model number 2680066 on a mercruiser 120hp 4 cylinder engine. I did all the bellows, gimble ring, and water pump before taking it out during the summer. At the end of the season was giving me a really hard time shifting into reverse. It would grind but if I went in and out of reverse a couple times it would eventually engage. It really only happened for 2 outings then I pulled it in for the season because I didn't want to cause extra damage.

What I've done so far:
I replaced the throttle cable, lower shift cable, lower shift shaft and bushing/seal and did a ton of adjusting trying to get it to engage cleanly. I then assumed the problem was in the drive so I dropped it off at a shop because I didn't want to buy more tools and I wanted a professional opinion. They changed all the seals for me in the lower and said the gears look fine. In the mean time I bought a whole other outdrive (same type same engine upper and lower) and slapped that on there. Same thing. So now I'm leaded to believe the problem isn't in the outdrive at all.

And heres some troubleshooting I've done:
I've taken the lower shift cable off the shift mechanism to pull and push the cable manually. Forward goes in easy and reverse only starts to engage at nearly the end of range of motion of the cable. I can physically verify that the bucket shaft and lower shift post are completing their range of motion because the bucket goes far enough to hit the housing of the drive. Which points to the problem being in the lower unit.

My current theory is maybe when I put the new lower shift shaft in the lower unit that maybe its directional and could be off a tooth in the spline? Has anyone had any similar experience or input?

Thanks for your help
Adam

 

[crazy charlie]

Since you have 2 different drives doing the exact same thing ,I would assume the shift cable needs a slight adjustment.You added that when cable was disconnected and you shifted manually it STILL did the same.THAT would point to the drive.Try splitting the drive and being sure the lower is fully engaged in FWD before mating the halves back together.Be certain that the shift arm is pointed straight forward.Put some grease on the top of the little spline and make sure there is a rubber washer under a stainless washer on that spline.Charlie

 

[wrench 3]

Did you adjust the cables by the book? The slot adjustment in the lever at the ignition interrupter gives it more travel into reverse.

 

[adam_man]

To adjust the cables I referred to this post:
http://forums.iboats.com/forum/engi...hifts-smooth-into-forward-grinds-into-reverse

I've seen quite a few instructions to adjust the cables but this one was the most straight forward to me.

I have found that if I adjust the cables to where they put a fair amount of tension on the lower shift cable that reverse will slightly engage. Is having the cables in tension or compression while being in gear normal? Or should the cables simply be positioning and not applying any constant force. I'm not sure what exactly the shift fork looks like in the lower but is it possible that both of my lowers have a bent one?

 

[Lou C]

I've never set up a Merc but when I did my Cobra I also had grinding and what I found was that I was not getting the same travel in each gear. The lower **** cable was adjusted right but the one from the remote control to the engine shift bracket was not moving the lower cable far enough in the gear that was grinding. I found the neutral position on the lower shift cable and measured the travel and then saw what the problem was. Adjusted that cable all was good.

 

[wrench 3]

The one series adjustment is basically the same as the Alpha but the mechanism is some what different. You might be better to go to http://boatinfo.no/lib/mercruiser/ma...uiser1.html#/0 Clear the page numbers at the center bottom of the screen and enter 95.
The cable shouldn't have pressure on it when in either gear. Make sure that you rotate the prop in the correct direction to let it go into gear when making the adjustments.

 

[mr 88]

You can also You Tube it and get a video of how to do it.Just punch in Mercruiser 120 shift cable adjustment.

 

[adam_man]

Nice, that manual has an excellent write up about it. Although wouldn't the fact that manually moving the lower shift cable all the way in and out with not positive results prove that the problem isn't in the cable adjustments? I was looking at this thread:
http://forums.iboats.com/forum/engi...hrow-in-lower-shift-cable-to-get-into-forward
it seems he has the same problem but opposite. Would not pulling the drive off in forward cause a problem like this to happen? Honestly when I first got this boat years ago it was a project and I just went at it without any manuals or direction. I have experience as an automotive mechanic and that was my excuse, poor excuse albeit.

 

[wrench 3]

I see where your coming from with manually moving the cable. But I had one that blew the upper gear set. I completely disassembled the lower unit to clean and reseal. put it back on and it wasn't going all the way into gear. Disconnected the lower cable and did the manual push pull. Could have sworn that it still wasn't right and thought I must have messed something up in the lower. Luckily I decided to do a complete cable adjustment first and that fixed it. Also you mentioned that you tried another complete drive on there with the same effect. They're not prone to having problems with the shift mechanism in the drive, so I can't see you getting two bad ones.
I just noticed your post count and realized that no one welcomed you to iboats. So WELCOME, it's always nice to see new members on the forum.
BTW were did you get your mechanics training? Around here the first thing they teach a new apprentice (right after they teach you how to sweep the floor) is "if you don't know get the book".

 

[adam_man]

Okay, I'll try that when I get to my weekend coming up. I ordered a shift shaft tool also to inspect the shaft in case the adjustment doesn't work.

Thanks for the welcome, been reading here for a while. And not to tangent too long, but I was a part time mechanic to get me through college at a shop I would never recommend anyone go to. First day of work I was told to do a head gasket, and that was the extent of my instruction. After 3 years of that though I picked things up. Now am a licensed 3rd asst engineer for ships. Small boats are much different than what I'm use to though! But thats why I always prefer DIY, never know if some idiot 20 year old is going to be working on it charging full shop rate.

 

[wrench 3]

With what you've accomplished since, I doubt that you were ever a 20 year old idiot. Just an inexperience 20 year old.