Mercruiser Alpha One won't shift into reverse with engine running

[rhorlacher]

I am aksing for some desperate help. I was determined to figure this out on my own, but that is not working. I have a 1986 Mercruiser Alpa One, Gen One drive that was not shifting into reverse easily. (It was clicking and always clunked into gear) I tried adjusting it on my own, but sliding the lower cable end up (away) in the slot. This had no affect on the cable and it after a few times shifting into reverse and the dogs grinding it did not shift into reverse at all. This lead me to believe I needed a new lower cable.

This weekend, I replaced the lower cable and followed the instructions in the manual on how to install. Out of the water and with the engine not running, shifting the drive locks the prop in both directions very nicely with what I think it normal shifter throw (Maybe 15 deg). However, when I fire the engine up to try shifting, I have no reverse. Forward gear shifts smoother than it ever has, but the engine just revs going into reverse. I have gone back and tried adjusting the reverse by sliding up the cable end again, but still nothing. I was thinking it could be the shift interrupt, but would think that would affect the forward as well.

Any help you can give would be more than appreciated.

 

[Rick Stephens]

You can tell if it is the interrupt just by watching and it would kill the engine if the lower cable stops or is stiff. I wouldn't expect it to have any effect on the unit not going into reverse at all.

You might watch achris's excellent adjustment video and follow his directions precisely. Start from a know correctly adjusted linkage.
https://www.youtube.com/watch?v=-s_tgevX2aI

You can also, in the water, just disconnect the lower shift cable and push pull it into and out of gear. If it won't go into reverse by hand then something else is wrong.

Rick

 

[rhorlacher]

I think I am going to try and do the shifting by hand as you suggest tomorrow and see what happens. I am up for trying anything. I am also doubtful that it is the interrupt as it seems to be working fine in forward. Thanks for the suggestions.

 

[Rick Stephens]

Best of luck with it.

 

[rhorlacher]

As an update, I am still at the same place, and believe I probably need a professional look. What I did last night was to remove the top shift cable and move the lever back to pull the boat into reverse and nothing happened. When I shifted it into forward it worked perfectly.

Next I removed the end of the lower shift cable and left the barrel in the cable rack. When I shifted into forward it worked great. However, when I pulled out (reverse) there was nothing. At the end of the travel it did seam that the dogs might have been rubbing, but it would not click in. It almost seams like the cable needs just a fraction more travel.

Before I go and pull the boat I am going to make sure nothing is behind the shift lever on the out drive, not allowing it to go into reverse. However, if anyone else has any suggestions I am all ears.

Thanks for the help so far.

 

[Rick Stephens]

I would be pulling the leg off and inspecting the linkage and then seeing if it will shift into reverse by hand. The shift shoe should be easily rotated by hand with the leg off, with the shoe pointed straight forward, the propeller should not turn in reverse without moving the entire gear train, With the shoe turn counter clockwise all the way, the propeller should be engaged with turned in the forward direction (propeller freewheels when turned forward while in forward gear with clicks of the dogs, and freewheels in reverse direction when in reverse)

I cannot think of anything you can do with the boat in the water. Pulling the leg is easily accomplished pretty much anywhere with a couple 5/8ths wrenches and a new gasket for when you reinstall. Make sure the gear shift is in forward so the shoe is pointing forwards allowing the leg to slide off.

 

[Fishermark]

May be time to check your shift spool. Here is a video I did a few years ago which explains it.

 

[thumpar]

The shift interrupt switch is only activated while coming out of gear and on the water.

 

[Rick Stephens]

The shift interrupt switch is only activated while coming out of gear and on the water.

As long as everything is adjusted and working right.

I had an older Alpha1 leg that after a half hour of use the shift linkage would get very stiff and activate the interrupt - in or out of water, into or out of gear. The entire issue was in the spool.

 

[Fishermark]

As long as everything is adjusted and working right.

I had an older Alpha1 leg that after a half hour of use the shift linkage would get very stiff and activate the interrupt - in or out of water, into or out of gear. The entire issue was in the spool.

The shift interrupt switch engaging when it is not supposed to (going into gear) would simply kill the engine.

the engine just revs going into reverse. I have gone back and tried adjusting the reverse by sliding up the cable end again, but still nothing. I was thinking it could be the shift interrupt, but would think that would affect the forward as well.

Since the problem is the engine is revving and the outdrive is not engaging in reverse gear at all, then the shift interrupt switch is definitely not the the problem. Not sure if it is a simple adjustment issue - or some serious internal breakdown. Some more tests are in order.

 

[Rick Stephens]

The shift interrupt switch engaging when it is not supposed to (going into gear) would simply kill the engine.



Since the problem is the engine is revving and the outdrive is not engaging in reverse gear at all, then the shift interrupt switch is definitely not the the problem. Not sure if it is a simple adjustment issue - or some serious internal breakdown. Some more tests are in order.

Agreed. Purpose of the conversation was to inform and elucidate.

The shift interrupt is not the problem. - The shift interrupt would definitely never effect things when the lower shift cable is disconnected and manually engaged.

Rick

 

[Eric 3.7LX Alpha 1]

Think I'd pull the drive off and have a look at the cable area (where the cable is screwed into the bellhousing) for build up/crud keeping the cable from being pulled back far enough..