1973 Mercruiser Straight 6 165 HP engine dies when going into reverse

[theck4291]

I already looked into the ADULTS ONLY discussion board, can't really find what I need to know so going here.

I replaced almost everything, my bellows, gimball bearing, the shift cable, spark plugs, wires, alternator and starter, plus a few other things, and I finally got it running again, however when i go to shift it into reverse it will engage, AND just barely run, but if I push it any further past it just engaging it kills the engine.

NOTE: When shifting into reverse, right when it dies, I can feel some tension in the shifter, then almost like a click, then it dies. Any help please? I tried adjusting the lower cable, and i set it to 6 inches like I am supposed to, just don't know what else to do...

 

[biggjimm]

It's your shift interrupt that's killing the motor. Mines doing the same thing. It's usually because if a bad lower shift cable but mine is good. I'm going to try to adjust the cables before anything else. Check out the adults only section at the top of the page in the stickies. There's stuff in there that explains the shift interrupt & lower cable replacement. Good luck. Jim.

 

[Fishermark]

NOTE: When shifting into reverse, right when it dies, I can feel some tension in the shifter, then almost like a click, then it dies. ...

As mentioned, it is your shift interrupt switch that is killing the engine. You need to discover what is causing the tension. 9 times out of 10 it is simply a bad lower shift cable. There are some other possibilities, but that is the best place to start.

 

[theck4291]

I already looked into the ADULTS ONLY discussion board, can't really find what I need to know so going here.

I replaced almost everything, my bellows, gimball bearing, the shift cable, spark plugs, wires, alternator and starter, plus a few other things, and I finally got it running again, however when i go to shift it into reverse it will engage, AND just barely run, but if I push it any further past it just engaging it kills the engine.

NOTE: When shifting into reverse, right when it dies, I can feel some tension in the shifter, then almost like a click, then it dies. Any help please? I tried adjusting the lower cable, and i set it to 6 inches like I am supposed to, just don't know what else to do...

It is not a bad shift cable

 

[theck4291]

biggjimm.... let me know how your adjustment affects your problem, please. Thank you

 

[biggjimm]

Theck, adjusting it did nothing. I'm at a loss too.

Fishermark, you say there are a few other things that can cause this also? What might those be?

 

[theck4291]

biggjimm, when you replaced the shift cable, did you turn it to only 2 threads visible? I saw something about that in the manual..... ;I understand that it can't have more than 2 showing, but what if there is only 1 or maybe even up to 2 threads deep?

 

[biggjimm]

I didn't replace mine so I'm not sure. Some of these guys will probably chime in before long & help you out with that information.

 

[Fishermark]

A somewhat common problem is a bent intermediate shift shaft. It can happen when someone tries to remove the outdrive with the unit in something other than forward gear. You might check to make sure it is straight.

Otherwise, as mentioned, you need to find out what is causing the tension in the shifter. Try disconnecting the cables and see how the shifter operates. Start hooking things back up one at a time until you find the problem. Try disconnecting the lower shift cable and see if it operates smoothly by hand.

 

[theck4291]

Took me a second to look up what the intermediate shift shaft is lol... No, mine is perfectly straight, was in forward when I removed it and it slid very nicely back in... What do you mean if it operates smoothly by hand? just pulling on the cord or what do I do? thanks for the help

 

[theck4291]

Found something here, check this out, I am at school away from the boat right now but in about 2 hours I am going to see if it works for me... Hopefully it helps you guys
http://dolphinmarineservice.homestead.com/cable.html

 

[Fishermark]

What do you mean if it operates smoothly by hand? just pulling on the cord or what do I do? thanks for the help

Yes. Disconnect the shift cable where it connects inside the boat. Then push and pull the cable. Have a helper turn the prop by hand while you do this. Engine off of course. ;-)

It should go in and out very smoothly and easily. If there is any unusual resistance, then you will need to find the cause.

 

[Fishermark]

By the way - the cable you replaced. Did it screw in from forward or aft of the bell housing? The new style cable screws in from the aft, while the original style screwed in from forward. You would have needed to do some modifying to fit the newer style cable in - unless it had already been done.

 

[theck4291]

Ok home now and looking into some stuff.. Quick question.. I have the older style shift interrupter, its no longer in production, model number 39670a28... ummmmmm.... the wires on mine are not hooked up tp anything... so what does that mean!?!??!?!?!??!!!!

 

[theck4291]

I had to modify it to fit for the new style... was a pain but got it and did it right....

 

[Bt Doctur]

the interrupter grounds out the ign to allow a coming out of gear in the water event.Being you say the wires were never connected, it cant kill the motor shifting.
If the new cable was not installed all the way(less than 2 threads visable) it will operate the switch, but again not being connected it wont kill anything.
Not having it connected will make it very difficult to come out of gear.

 

[Fishermark]

I had to modify it to fit for the new style... was a pain but got it and did it right....

Since not much time elapsed between you saying the switch was not hooked up to saying it has now been fixed.... I take it you didn't just go out and make this fix, correct? In other words, you have had the new switch hooked up for awhile now, right? Otherwise, like the doc says, it wouldn't make sense as the switch couldn't kill the engine if it was not connected.

 

[theck4291]

No, that post is about the shift cable.... It had the old style shift cable at the bell housing and I had to buy the tap and drill out the threads from inside.... There are TWO shift interrupters on the boat, the one I mentioned that is not attached, and there is one on the opposite side of the shift assembly that IS connected and works properly, and It is COMPLETELY different and much bigger.

I found out a little more about the ratcheting in my shifter... I disconnected it and it still ratchets from the shift assembly in the engine and it still ratchets, and ideas? And I am readjusting the shift cables right now as I think I adjusted them improperly last time

 

[theck4291]

WOOOOHOOOO!!!! Got it working right.. It was just the freakin adjustment... I thought I HAD adjusted it properly last time, but I found a SEI video on youtube that was for Alpha 1 or Alpha 2 gen, and mine is MC1, however even though the shift assembly is located differently, and there are a few other features I dont have, following their EVERY step fixed mine...

BIGGJIMM this is the video I used, did you do exactly the same thing as he did? If not give a try and let us know what happens!! Hope it works out for you!

 

[biggjimm]

If the wires are not hooked up, the interrupt would not be killing the engine. Are you sure you're looking at the interrupt switch? On mine which is a 76, yours is probably similar, it is a brown wire going from the coil - terminal to the interrupt switch & a black wire going from the interrupt to ground. Mine is located on the shift plate right above the power trim pump on starboard side of engine at the transom.