'71 85hp Electric Shift Question

[Speeder]

I've looked at several previous posts but none of them sound exactly like what I'm experiencing.<br /><br />Background<br />At slow speed reverse (or even neutral I think) the boat has jumped into forward. Pretty scary while docking. At other times there have been some rapid severe Bang Bang Bangs which I'm pretty sure was hopping in and out of gear (I think that might have been reverse too). <br /><br />Otherwise the boat motor has run fine for several years though I admit the electric shift buttons are getting a little tired in regards to the sliding plastic plate lockout gizmo. They seem a little spongy and I suspect it's possible that they can be pressed when they aren't supposed to be able to (I've lived with the problem for years). Also, I did hit rocks pretty hard recently and I'm concerened that might have led up to this problem.<br /><br />I talked to a local repair place and if I recall he said it could be the hydraulic pump that might not be supplying enough pressure or some other issue lower unit issue I can't recall.<br />The shops are all booked up so a mechanic friend and I are going to tackle it. <br /><br />So here's the question: Can anyone recommend a diagnosis procedure to save us the misery of working on switches when it's the lower unit or vice versa?<br /><br />Thanks in advance.

 

[Dhadley]

Re: '71 85hp Electric Shift Question

Welcome!<br /><br />Keep this in mind -- its not an electric shift. Its a hydro-electric and very different. It helps to remember that when trying to figure out problems like this. <br /><br />The unit is loaded (no power) in forward (not neutral like an electric shift). It takes hydraulic pressure to get it out of forward. If the wrong oil is in the unit or the right oil is watered down it will try to jump back into forward. <br /><br />I would try some fresh, correct oil first.

 

[mrc]

Re: '71 85hp Electric Shift Question

A word of warning... finding a snap ring tool long enough to extract the oil pump is a bit of a challenge. There is a special extender tool called for with the OEM manual but I have not yet obtained one.<br /><br />Before tearing down the lower unit, I would recommend temporarly disconnecting the shift solinoids from the wiring harness (couple of knife connectors near the back starboard side of the engine) and wiring them to a "running/anchor light" switch (push,pull, pull some more) which is directly wired to the battery. Frankly this sound more like an intermittent power loss to the shift solinoids than a problem with the lower unit oil pump.

 

[JRuggiero]

Re: '71 85hp Electric Shift Question

I can shed some light, an I've just done alot of electrical work on my '71 60hp.<br /><br />This is the entire system, sorry if you've ruled out electrical already...<br /><br />Find the two knife connectors for the shift wiring, aft side of the powerhead running down to the lower unit. Undo these, one wire is blue and one wire is green. Turn your key ON and connect the positive lead of a volt meter to the green wire, the ground of the meter to ground.<br /><br />In forward, there should be no voltage to this wire. Neutral should be 12v. Now, watch the meter and go from forward to neutral and back and forth. Make sure you go 0v to 12v respectively. The blue wire can be checked for reverse (both wires receive 12v).<br /><br />Now do the same check with the motor running. The first check will verify wiring and the shift switch. By starting the engine, you will be powering the shift safety circuit. This is a diode (looks like a hard glob of dark something hanging of the motor) that provieds power to the shift system via that stator to prevent the lower unit from popping into forward when you turn the key off (prevents lurches at the dock). Check for your nice 0v/12v while switching back and forth. If that's all good, move to the lower unit.<br /><br />You can test the two diodes by using an ohm meter. Connect one lead to the green wire (the end going down the leg) and the other end to ground. You should get 5-6 ohms. Same for the blue wire. If this checks out, keep reading.<br /><br />Drain the lower unit oil. Is there metal? Is it frothy with water? Was there not much in there? These are all bad. Replace with Type C (5 bucks or so for a quart) from the lower drain hole until it comes out of the upper hole. You can also fill and drain the LU with dextron - never done it, but may help clean the hydrolic pump.<br /><br />Good luck!

 

[Speeder]

Re: '71 85hp Electric Shift Question

Thanks for the great info guys. I'm hoping I found two smoking guns. One, it just ocurred to me that I was unable to find any local source for the correct OMC Premium Type C gear oil last year. I remember asking around for suggestions which led to a supposed close equivelant 90 weight NAPA hypoid gear oil (I think the OMC is 85 weight hypoid). Anyway, now that I have the correct stuff this year, it is noticeably thinner viscosity than what came out.<br /><br />Also, I was startled to see when we drained it that there wasn't that much oil in there, seemed like a little over one tube (very clean however). Then I recalled the difficulty I had pumping the stuff in by hand with the tubes. I know I filled until the top hole oozed but I suspect there might have been air pockets. So we did a little flushing out in case there was plugging or sludge, still no sign of metal. Finally I used a hand pump set up, what a difference. We could hear a lot of burping and I know it took on more volume than last year. <br /><br />So I'm sheepishly reporting that I think it may have simply been the combination of slightly wrong oil and not enough of it. I'll still do the solenoid checks you recommend before it goes out however.<br /><br />Thanks again, I sure wish the car site I go on had the quality of responses this one does.

 

[papasage]

Re: '71 85hp Electric Shift Question

looking for a site on aoto transmishons .thanks