1989 Mercruiser Alpha one Gen one Shifting problems

[SeaRay2389]

One day it was shifting fine the next it woundn't come out of forward or reverse gear without turning the key off. It seems to idle down low enough even though my tach reads 900 rpm. I took it out of the water and put it on the muffs when I got home and it was doing the same thing until I took the prop off. It seemed to shift fine with the prop off. Any help is appreciated.

 

[alldodge]

Check your shift interrupter switch. Have the motor running and reach back there and depress the switch with your finger and see if it makes the engine stumble or die. If it does, you need to readjust the switch

The alpha drive will shift in and out of gear on muffs because there is no pressure on the prop, but it will not shift out of gear without the shift interrupter.

 

[Fishermark]

Definitely something amiss with the shift interrupt circuit. Like Alldodge mentions, engage the switch with the engine running. The engine should die. If it doesn't, the switch is either bad or the wire has been disconnected. If it does die, then it may indeed need adjusting. (But that is not common) Here is how much it should move before interrupting the circuit:

 

[SeaRay2389]

Thanks for the replies and advice. I figured it had some thing to do with electrical but didn't know where to check or look. I'll check out that switch and let you know.

 

[SeaRay2389]

I checked the switch out and the engine didn't die when triggered. Looks like I need a new switch. Thanks for the help.

 

[Fishermark]

I checked the switch out and the engine didn't die when triggered. Looks like I need a new switch. Thanks for the help.

Make sure the wiring has not been removed or broken off or corroded, etc. before simply buying a new switch. Use an ohm meter and see if the switch has continuity when engaged.

 

[SeaRay2389]

Yes sir I checked out the wires and continuity also. Do you know where to buy or a part number?

 

[Rick Stephens]

The original part number should be #39670A28. I tried to find that on iBoats and could not.

 

[SeaRay2389]

Is there a part that supersedes this par number? Or a retro fit kit? I haven't had much luck finding a new part that isn't over $200. As far as I am told they don't make this part anymore. I'll pay the asking amount if that's all there is. I have found used but really don't want a used one that may fail also. I have gotten mine to work intermittently but the trigger thingy must be moved way more than it should. Its very inconsistent.

 

[Fishermark]

I wouldn't be afraid of used as the switches do not fail often. Certainly before spending $200!

You say the switch does engage finally, but you have to pull it further than the 1/8th inch that is normal. The spring lever can be bent so it works within the necessary parameter. Try that first.

 

[SeaRay2389]

I wouldn't be afraid of used as the switches do not fail often. Certainly before spending $200!

You say the switch does engage finally, but you have to pull it further than the 1/8th inch that is normal. The spring lever can be bent so it works within the necessary parameter. Try that first.

Thanks for the info. I have bent the spring with no success. I have to depress the button under the spring lever fully several times and it work as it should
occasionally. I did find that there is a update kit Mercuiser part #864363A 1. I don't know this for fact. Anyone know for sure if this will work on a 1989
Mercuiser Alpha one Gen one?

 

[Bt Doctur]

the new updated plate will work, but as mentioned the switch seldom just fails
I have a new plate ,pm me if interested

 

[SeaRay2389]

Problem solved! I got the new shift plate installed with new style interrupt switch and with some adjustments it is working again. Thanks for all the help.