engine dies in gear

[dixieboater165]

OK first time I was going to run the boat this year so I decided to put some muffs on it at home. The engine cranks, but when I try to put it in gear (forward or reverse) the engine dies. Is there some safety switch that wont allow it to go in gear out of water? Any help is greatly appreciated. 1987 Mercruiser 165 w/ alpha one drive.

 

[Don S]

Re: engine dies in gear

Bad shift cable (Stiff, corroded, kinked) causes shift interrupt switch to hold in the activated position that kills the power to the distributor.<br />Replace the cable.

 

[Trent]

Re: engine dies in gear

Sounds to me your lower shift cable is sticking and causeing the shift interrupt switch to kill the engine. This is a very common problem on Mercrusiers. Time for a new lower shift cable.

 

[dixieboater165]

Re: engine dies in gear

Where is the Shift interrupt switch and what is its purpose?

 

[Trent]

Re: engine dies in gear

Don did it again....

 

[Trent]

Re: engine dies in gear

The purpose of the switch is to kill the engine for a fraction of a second to release the gears. Normally adjustment of the shift assist switich will be required if the engine kills when shifted into gear. The mere fact that it is killing the engine proves that the switch is good, it is working at the wrong time(going in gear).<br /><br /><br />If the boat has no neutral, when you try to shift to neutral it fights you and passes from fwd to rev or rev to fwd, then you have a problem of a sticking shift cable or a sticking shift arm and roller on the upper shift shaft. This adjustment is addressed in part two of this page below.<br /><br /><br />The gears in the outdrive are undercut so once together they stick together if there is a prop load(in the water). When the forward cable tries to move the lower shift cable it fights the action and is felt as a resistance on the shift handle. Pressure on the lower shift cable shifts the arm that trips the easy shift switch, thus the engine starts to die. One second later during the lapse in h.p. the gears let go, then the switch resets and the engine regains power. The whole process takes only a second and the engine recovers with only a hesitation, which you hear (whooomp).

 

[Haut Medoc]

Re: engine dies in gear

It's purpose is to temporarily interrupt spark [imperceptible] which enables the gears to shift smoothly because they are not under load. I don't know your specific model, but I would guess that it's very close to where the cables meet on the engine. Don't waste your time messing with it, you need a new lower shift cable.

 

[Don S]

Re: engine dies in gear

The shift interrupt switch is located on the shift plate on the engine where the shift cables are attached, but adjustment is not an option. The cable is bad and that is why the switch stays engaged.

 

[dixieboater165]

Re: engine dies in gear

Ok well that sounds like that is the problem. Makes a lot of sense. Thanks everybody for the great help. New Shift Cable.

 

[dixieboater165]

Re: engine dies in gear

I took the outdrive off and took out the shift cable. I am going to get a replacement tomorrow. I figure that while I am in there I should replace the shift cable bellows. Looks simple enough, but how hard is it to do (get to the back clamp) without taking off the gimbal ring? Or can it be done? Close quarters in there. Also would it be wise to put some quicksilver perfect seal on the bellows where it attaches to the cable (skinny end) or does the cable have to slide a little in the bellows?

 

[dixieboater165]

Re: engine dies in gear

Ok, I got my new shift cable in and I followed the Clymers manual instructions to adjust it. The shift interupt switch still kills the engine when I try to put in gear. Sometimes it goes in gear and sometimes it kills it. What's the deal? I had some water freeze and strip out the retainer nut in the lower unit this winter. I got a new bearing retainer and retainer nut put in weeks ago. I had the lower unit all apart except for the forward gear, propshaft and driveshaft completely out. Could there be some resistance in letting the forward gear slide into the drive gear on the bottom of the driveshaft? (A result of water damage) Is this resistance causing the shift interrupt switch to stay on?

 

[Don S]

Re: engine dies in gear

Ok, I got my new shift cable in and I followed the Clymers manual instructions to adjust it.

Clymers?????? There's your first problem.<br />What you need is a real Mercruiser service manual.<br />Lucky for you there is one online.<br /> http://www.boatfix.com/merc/Servmanl/6/6covr3.pdf <br /><br />Also, while you had the drive off, did you check the shift shaft in the bellhousing on the transom. Did it move freely? If it was hard to move, that could also be part of your problem.

 

[dixieboater165]

Re: engine dies in gear

The upper shift shaft in the bell housing moved freely when I had the drive off; with the new shift cable and slide. The controls shift smooth as silk when the engine is not running but there is a little resistance in the handle when the engine is running. (I edited my previous post before you replied)

 

[Don S]

Re: engine dies in gear

Hope you didn't put any kinks in the new cable, they are real touchy about anything that causes a bind in the movement.

 

[dixieboater165]

Re: engine dies in gear

I dont think that it is kinked because it slides easily by hand and with control unit when the engine isn't running. Plus, I was extremely careful. I am reading the Merc manual adjustment instructions- how do I tell if my drive is a RH or LH rotation drive?

 

[Don S]

Re: engine dies in gear

Look at page 1A-1 in that manual link.<br /><br />It may be just way out of adjustment.

 

[dixieboater165]

Re: engine dies in gear

Ok, this Merc manual is way more thorough and explains things clearly. It is dark now, but I will follow these adjustment intstructions tomorrow. Thank you Don S.

 

[dixieboater165]

Re: engine dies in gear

I followed the instructions exactly, it still engages the interrupt switch too long and kills the engine when I shift into reverse. It works going into forward and it kills engine for a brief second going from forward into neutral, (like its supposed to) but it kills engine completely when I shift into reverse. Do you think that there could be a burr or something on the sliding clutch/gears in the lower unit that is causing my problems? (From the water damage I mentioned above)

 

[Don S]

Re: engine dies in gear

Anything is possible.<br />I had a Glasply years ago that also died when going into reverse, forward was ok. Turned out it was just a sticky shift interrupt switch. Once I replaced it, it worked fine. Never could figure out why it only did it in reverse.

 

[dixieboater165]

Re: engine dies in gear

There must be some resistance going into reverse: either in the lower unit with the clutch/gears or somewhere else. I can feel resistance in the shifter handle going into reverse- it's stiff. I don't know. But it works in forward and it will go into reverse if I have someone hold the shift interrupter switch from moving. I am just going to take it to the lake and run it in forward. If I HAVE to go into reverse I'll have someone hold the shift interrupter switch from moving. Maybe it will loosen up going into reverse and not activate the switch if I run it some. It's a long shot, but I'll try it and go from there. Thanks for the help.