OMC 5.8L Shift assist module

[shekinah5678]

Hello again. My friend has a 1990 OMC 5.8L with cobra drive. He has been having trouble getting it to shift in and out of gear and sometimes even when you shift to neutral it will stay in gear. I lowered the idle and that helped it to shift but still not rite. I took a look at the shift assist module and found that it wasn't even plugged in. I plugged it in and presto all was good. However I took the boat out for a test run and it stopped working. I found that the module is working intermitently. If I moved the wires around it would work for a while and then stop. I could just tap on the module with a wrench and then engage the rocker switch manualy and it would work for a while. My question is should I just go ahead and change the module out? It doesn't look that old to me the wires are all clean and you can still see the stickers. I wonder what could have made it go bad? I'm pretty sure the motor still has the stock points distrubuter but I will double check to make sure.

Thanks in advance!

 

[Bifflefan]

Re: OMC 5.8L Shift assist module

Its an electric part. They fail when they feel like it. As long as your sure its not a loose or bad wire, replace the unit and you should be fine.

 

[a70eliminator]

Re: OMC 5.8L Shift assist module

The switch is simple to test with a meter, heck dust a little 12v bulb and a wire is all you really need to check the switch, your problem starts with O and ends with C.. I mean you friends problem.

 

[bruceb58]

Re: OMC 5.8L Shift assist module

Run the engine and manually depress the shift switch and make sure it stumbles the engine. If it doesn't, then test the switch. Also, make sure the overstroke switch(if you have one) is in its proper state. It is normally closed and will open(preventing the stumble) if operated.

The fact that the drive stays in gear when you shift to neutral points to the lower shift cable being bad or needing adjustment. Don't operate the boat until you figure out which.

Tilt the drive up and look at the cable housing as it enters the drive on the starboard side. This is where these cables often fail as the housing pulls from the end. It is very hard on this shift cable if the drive is stored up for long periods of time.

Forget about testing the switch with a bulb. The amount of current going through that switch is likely very small since it is controlling the input of a high impedance device.

I would also suggest replacing the module. OMC changed modules eventually to one that uses a timer instead of relying on the overstroke switch. Not sure if 1990 had that new module or not. If you have an overstroke switch, you have the old module.

 

[shekinah5678]

Re: OMC 5.8L Shift assist module

Thanks everybody for the input. I talked to a local boat mechanic who happened to have a used shift assist module. I'm gonna buy it from him on the cheap and if it doesn't work I can return it. I figured that would be better than ordering a new one on the internet and then finding out that wasn't the problem.

 

[bruceb58]

Re: OMC 5.8L Shift assist module

I believe there are different ones for 4 cyl vs 8 cyl so need to check that.

 

[willywaller]

Re: OMC 5.8L Shift assist module

I was having an intermittent reply with mine. I had a mechanic remove it and he rewired to get the same effect. Works great now, easy shifting.

 

[shekinah5678]

Re: OMC 5.8L Shift assist module

I believe there are different ones for 4 cyl vs 8 cyl so need to check that.

Thanks, the one my mechanic had was for a V-6. I ended up buying one on line. Seemed to fix the problem. Boat is shifting fine now. Thanks to everyone.