shift interrupt engaging while in gear

[biggjimm]

I know & understand how the interrupt works & why it's necessary. Here's my problem. I put my new cam & lifters in & the head back on this weekend on my '76 140 mercruiser.

I think while it was apart the linkage rod that hooks to the carburetor got turned a few times & is out of adjustment. Now the shift interrupt will engage while in gear. It does it in reverse every time & occasionally in forward gear. As soon as it goes into reverse it activates the interrupt. When it does it in forward gear it's at about 2/3 throttle & it will activate it.

It does it more when it's shut off & just working the shifter back & forth. I can feel the slightest bit of change in the shift mechanism. It's not quite as smooth.

Could this be because the carb linkage rod out of adjustment? Thanks. Jim.

 

[alldodge]

Could this be because the carb linkage rod out of adjustment?

Wouldn't be my first guess. I think you just need to go back through the shift cable adjustment form Chris's video in the Merc sticky section. Before doing the shift adjust I would remove the throttle cable from the carb and adjust it for slight bit pressure closed or at zero effect.

 

[Bondo]

Wouldn't be my first guess.

Ayuh,.... My 1st guess is a tight, draggin' lower shift cable,.....

 

[biggjimm]

The lower shift cable was fine. It operated nice & smooth. I checked it during & after I had the bell housing off replacing the bellows. I was extra gentle with the bell housing as I read that most times the cable is damaged when the bell housing is removed. That being said, I'll check it again Bondo.

It was working perfect before I took the linkage off of the manifold when I pulled the head. I suppose I'll just check that video AD mentioned & see what I can adjust if the lower cable is still moving freely that is. Thanks guys.

 

[philbullet]

Every time I started to have trouble like that with my 470 I had to change shift cable, it seemed smothered when moving my had but just wasn't quit enough for the interrupter switch to work correctly while boat was in water, not on trailer.
It seemed I was changing it every 2 years.

 

[biggjimm]

That'd probably where I'm headed but just want to make sure because it was fine & then it started acting up after my cam change & head gasket.

Let me add this, I forgot to mention that I had to pull the drive because I needed to remove the front mount & raise the engine up to allow the cam to clear the bulge area/ floor of boat. Could something g maybe be goofy in the shift slide & little roller thing on the arm in the bell housing? When I pull the drive off, the cable & the slide thing turn about a full 180? down & away from the roller on the arm of the upper shift shaft. Last time I just themed it back up to where it was supposed to be & it was fine. So, I wonder, if this time I turned the slide the wrong way or something & that's causing it to bind?

I'll check that I guess & then replace the lower cable. I just can't see it going bad from one weekend to the next sitting in the drive. We'll see. Thanks guys & I'll let you know. Jim.