shift cable adjustment and engine dieing problem -- hopefully related?

1980 vintage Mercruiser 165 that has gotten a lot of work in the last months bringing it back from years in mothballs. On muffs I thought all was ok and ready for the water. Took it to the lake Sunday and discovered two hopefully related problems. So once again seeking guidance from the literate.

The boat got a new shift cable. It goes in to forward gear fine. Doesn't go in to reverse. Has what feels to be full travel of the lever rearward but not getting to reverse. Apparently the puzzle that was adjusting the shift cable I got wrong somehow and need to deal with again.

Second thing is the engine dies... no, the engine is killed when you come out of forward gear and come back to idle/neutral. Initially thought the engine was dieing but quickly realized it wasn't. If you're in neutral and have run the rpms up a bit and drop back to idle it stays running fine. Be in gear and bring the lever back far enough to reach idle and it stays running. Bring the lever back the rest of the way to actually reach neutral and it kills the engine. So am assuming something going on with the shift interrupt switch?

Question before I take time to look at it again later in the week is if the shift cable adjustment alters the interrupt switch's adjustment? Just wondering if chasing one problem or more likely two?

Re: shift cable adjustment and engine dieing problem -- hopefully related?

The shape and cut of the gears in the outdrive causes them to stay engaged if any load is present. This causes a drag or resistance on the shift cable when coming out of gear. The shift interupt sense the extra load & cuts the engine for a fraction of a second to release the gears ( when everything is working as intended. )


You can watch the interupt mechanism move and ensure that's what causing the stalling problem.

1 fairly easy test;


If you excersize the cable with the motor OFF it should not engage the shift interupt. If it does then thier is something wrong.

Re: shift cable adjustment and engine dieing problem -- hopefully related?

wellcraft-classic210 said:

If you excersize the cable with the motor OFF it should not engage the shift interupt. If it does then thier is something wrong.

Click to expand...

Just a note of clarification here. With the engine off, if you shift and the shift dogs happen to be on the high points, it will activate the shift interrupt switch.
With the engine running on muffs (no load on the prop) you should be able to shift forward, and reverse, in and out of gear, and NOT activate the shift interrupt system.

The shift interrupt system, when working properly, only activates when coming OUT OF GEAR when the boat is IN THE WATER.

Re: shift cable adjustment and engine dieing problem -- hopefully related?

What you're both describing is what is happening; just not momentarily. If the boat is in gear and I bring it back to neutral the engine is killed. I can bring it back to idle just short of neutral and the engine stays running. But swing the shift lever that last bit necessary to drop out of gear and the engine is shut off.

If as described above the shift interrupt offers only a momentary cut out of engine torque rather than a full shut down, and it does so only if the system is normally loaded as it would be in the water rather than on muffs, it sounds like this may be a quirky adjustment to know you've got right if dealing with it on muffs in the driveway. Any helpful insights beyond what's described in the manual from or is this one a case of sitting with the book?

Re: shift cable adjustment and engine dieing problem -- hopefully related?

Thier is no adjustment for cable friction. Thier is however a spring on your shift interupt mechanism that needs to be in place.

The most common fix is replacing the shift cable as they tend to cause drag when worn , damaged or lubed. (The cable is designed to run without any lubricant, lube will tend to gum up over time. strange but true ).

I compared a Sierra cable to a Merc recently & found the Merc cable is a much better design that's less likely to cause a binding problem. Use caution not to place any extreme bends on it if you and up installing one.

Don S. --- Thanks for clariifying my post above. Nothing beats the voice of experience! ---

Re: shift cable adjustment and engine dieing problem -- hopefully related?

wellcraft-classic210 said:

Thier is no adjustment for cable friction. Thier is however a spring on your shift interupt mechanism that needs to be in place.

The most common fix is replacing the shift cable as they tend to cause drag when worn , damaged or lubed. (The cable is designed to run without any lubricant, lube will tend to gum up over time. strange but true ).

I compared a Sierra cable to a Merc recently & found the Merc cable is a much better design that's less likely to cause a binding problem. Use caution not to place any extreme bends on it if you and up installing one.

Don S. --- Thanks for clariifying my post above. Nothing beats the voice of experience! ---

Click to expand...

This one has a new shift cable. Was replaced while a lot of other work was done over the last several weeks. The original had a kink and a split housing so its continued use wasn't a question.

The microswitch itself is functioning as would be expected when checked with an ohmeter. The twin armed spring is there but of course I've got no idea how much pressure it should have pushing back against the mechanism.

The cable that came out screwed in to the housing from the front. Everything would have to be taken apart for its replacement. The new cable that was recently installed screws in from the rear. It can be replaced with only removing the drive. I don't know, however, if this replacement cable was a Mercruiser part or a Sierra part. It was (supposedly) new. Looked new. But had been opened and was packaged in a large baggie when I got the boat.

I did lightly lube the cable before its final install in to the housing though. So I screwed the pooch a bit. Sounds like that's a mistake that would present itself as a problem over time rather than initially though

I'd be content if all that was required was a shift cable. Even happier if I just need a thorough cleaning of the mechanism in place and make sure the spring is good. Found out the switch itself is obsolete. There is an updated Mercruiser parts assembly to replace it. But the service note said changing that switch assembly also required changing the trim pump. So it quickly gets up to an $800-or-so repair. The old boat was cheap to begin with and still have less than its likely value in it after its resurrection work was done. Another $800 would spoil a lot of my fun on the old project though...

Re: shift cable adjustment and engine dieing problem -- hopefully related?

I'd start by disconnecting the shift cable and make sure it moves smoothly in and out of gear. There should be almost no resistance. Possibly the cable was kinked during the install. I ran into a problem earlier this year when I had the "Y" bracket over tightened so that it didn't move freely. Acted like a bad cable.

Re: shift cable adjustment and engine dieing problem -- hopefully related?

Nola mike is definitely on to something there. Eliminate all the big problems first, by disconnecting the cable and shift it back at the motor. If you have a bucket, you should be able to replicate at least some "load" (large garbage can usually works but make need to rest on a cinder block or something to get it high enough) and it would be ok to engage both forward and reverse that way. Plus, with a trash can instead of muffs, you'll be able to better adjust the cable if that's where the problem lies.

Re: shift cable adjustment and engine dieing problem -- hopefully related?

If you go "bucket route" keep the hose nearby as the prop will throw a lot of water out pretty quickly.

Re: shift cable adjustment and engine dieing problem -- hopefully related?

Thanks guys. A weekend chore is hopefully to do just those things you've described and hope I can at least isolate the problem if not actually sort it out. Was going to ask if using a large bin or garbage can was a viable option. So you've answered a question even before it was asked.

Re: shift cable adjustment and engine dieing problem -- hopefully related?

if you lubed that cable....its junk......replace it and save yourself headaches..