3.7 mercruiser shift linkage.

[ctaylor2069]

Is there a sticky somewhere for adjusting the shifting linkage on my mercruiser? If I start the boat and go in reverse it won't go back forward into neutral until I shut the motor off. And same with forward. So a buddy put a little pressure on the linkage and it shifted better. Just curious if it's kinda a adjust as u go thing. Thanks

 

[stonyloam]

Your shift interrupt switch is not working properly. Go to the "adults only" section (topic #9), there is an explanation of how it works.

 

[ctaylor2069]

Thanks. I was hoping there was a sticky or something I just must have overlooked it.

 

[ctaylor2069]

So after reading about this is it adjustable or does it likely need replacing?

 

[stonyloam]

OK, In your case it sounds like the switch is not grounding out the coil. Take a look and see. The switch lever with the little wheel on it should be centered in the "V". You can start the boat on muffs and push on the lever, the engine should die. If it does not you probably have a bad switch. On the water, in gear, idling along, have someone watch while trying to pull the control handle out of gear. The little wheel should move out of the "V" and move the arm to close the switch, killing the engine for a second or two. Make sure the wires are in good shape. With the engine off, take a voltmeter on ohms and test the continuity between the coil - and the switch, and between the switch and ground.

 

[ctaylor2069]

Ahhhh thanks stoney

 

[nola mike]

People frequently disconnect these when the lower shift cable is bad.

 

[ctaylor2069]

People frequently disconnect these when the lower shift cable is bad.

Could you elaborate a little bit more? I thought these had to be hooked up ? Is there a way to work around it?

 

[stonyloam]

If your lower shift cable is worn it gets sticky, so when you go to shift INTO gear the sticky cable puts pressure on the plate and the cutout activates killing the engine. In other words when you are shifting into forward the switch " thinks" you are trying to pull it out of reverse and since the pressure is not released the engine dies. So folks will disconnect the wire to prevent the engine stalling, how they get it out of gear, I do not know

 

[nola mike]

The shift interrupt briefly drops the engine rpms so that the outdrive can engage the gears. When the shift cable is bad, the switch doesn't return to position and the engine dies. As a half assed fix, people will disconnect the switch (and sometimes lower the idle speed) so the engine doesn't die. But this makes the shifting difficult. The work around is to replace the shift cable. But we're getting ahead of ourselves. Try terry's tips first; just hold down the shift lever so that the roller is out of the "vee". It should kill the engine, and that lets you know that your switch is hooked up and working

 

[nola mike]

how they get it out of gear, I do not know

They lower the idle so that it barely runs...

 

[stonyloam]

Hey mike, most guys here think 470s barely run all the time LOL.

 

[nola mike]

Even on its best day mine sounds like a diesel rabbit on 3 cylinders at idle.

 

[ctaylor2069]

So I hooked up the muffs and fired up the engine , just like Mike mine sounds like a 3 legged dog. Anway. I manually engaged the switch by hand and couldn't notice a drop in rpms or a difference in anyway

 

[nola mike]

So next step is to see if you have 2 wires to the switch. There should be continuity when you trip the switch. 1 wire goes to ground, the other to the coil negative

 

[ctaylor2069]

Ok so check continuity with the volt meter on ohm's?

 

[ctaylor2069]

Also I keep hearing talk about this lower shift cable. Is this the one that runs through he transom? Is it something I should have replaced when I did my bellows last week?

 

[nola mike]

Yes, and probably
If there was ever water in there, then it probably should have been replaced.

 

[ctaylor2069]

Ok ill check the continuity. What's this I keep reading about a lower shift cable? Is this something I should've replaced when I did my bellows about a week ago?

 

[ctaylor2069]

Yes, and probably
If there was ever water in there, then it probably should have been replaced.

Thanks , that would've been helpful to know when I did my bellows lol. Always something.