Tight shifting from neutral to forward or reverse, 1979 OMC 120

anderso8623 · Jun 5, 2013

When shifting from either neutral to forward, neutral to reverse, or back to neutral from either direction; I have difficulty. I must essentially slam it into forward, reverse or neutral, causing the RPMs to spike.

The shifter is very stiff when in gear. I pop it into the neutral position and rev it and the slide is smooth and effortless.

The shifter is a single handle shifter with neutral between forward and reverse. When in neutral, you can pull the handle out to rev it either forward or reverse. Neutral is very difficult to find as I often over shoot it due to the slamming into and out of gear.

Following the shift cable back, I have a shift box. The cable running from the shifter ends in this box and is connected to a "pulley-like" set up. From the box to the lower unit is the same type of cable. The two cables consist of metal cables inside the actual cable. At the ends that go into this box, there is cylinder like connectors to connect the cables to the pulley system.

I am not sure what is causing this stiffness or if it natural for an older design such as this one. I have asked around about the cause and people have suggested a tension screw in the shifter; when I asked the local shop they said there was none in this model.

I will try to post pictures later on to help explain but I do not get home till 10:30 or so.

Thank you
,

Jason

Howard Sterndrive · Jun 5, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

Is this a new-to-you boat? Or have you ever seen it work right? And if so, did the problem get gradually worse, or did it start acting up suddenly one day?

anderso8623 said:
I pop it into the neutral position and rev it and the slide is smooth and effortless.

good info - that proves your shifter lever itself (and the throttle cable) is fine.

A side-on picture of the sterndrive would be good. Would be good to see if the lower unit is a 1979, or a mismatched mechanical unit on there.

But behind the engine is a box called the "shift converter" and in/on there, your helm cable meets the lower shift cable - that's the point you would want to go to to determine which cable or "half" of your shifting system is causing the stiffness.

anderso8623 · Jun 5, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

The boat is new to me. No prior experience other than in my driveway and once on the lake. It has always been stiff

The lower unit is white, uses an electric powered gear to raise and lower the unit exposing the exhaust. The engine is a blue Chevy...2.3...I think...

As for the shift converter, this is the "**** box" I was referring to. I have had it opened before and actually disassembled it to remove the lower unit for water pump replacement...did not need one... I put it back exactly the same way and as I said, it always shifted stiff.

With the shift converter, how would I determine the stiffness of each side? i.e. would I tug on the wire cable?

Thank you again!

Jason

Howard Sterndrive · Jun 5, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

anderso8623 said:
The lower unit is white, uses an electric powered gear to raise and lower the unit exposing the exhaust.

we'd be looking for something else in the pic - the presence or absence of a zinc anode above the propeller in a rectangular recess next to the 6 idle relief holes.

don't want you tugging on any cables until we see if you have the correct lower unit, but yeah basically you want to disconnect the helm cable from the box, then go up front and see if the shifter is still stiff.

If it is still stiff, then you need to replace the long cable from the shifter to the converter.

If it isn't, well then you'd want to unwind the lower unit cables from the converter box and try shifting with the cable wires in your hand- but that part depends which lower unit you have... and I caution you about unwinding the cables out of the converter box with 12V Battery power still in the boat - there's a lot of bare live terminals that will instantly fry that $700 cable if they touch 'em.

anderso8623 · Jun 6, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

Still working on pix. Should have them today. To start with, this is the model number right off the engine: 990243s.

anderso8623 · Jun 6, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

Here are my pix. Let me know if you need more

Howard Sterndrive · Jun 6, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

ok- you have the original and proper lower unit - it is a hydromechanical shift. Which means there is a pump in the lower unit and a shift assist servo that helps the drive shift.
Those plungers were famous for rusting and seizing anytime there was water in the lower unit lube - so that's something you want to check for. Otherwise, you could have a cable that has jumped off the guide inside the shift converter box.
and as mentioned, disconnecting the helm-side cable at the converter box is the first test to see if the helm cable might be the culprit (hopefully)

anderso8623 · Jun 6, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

I will check the helm cable first; if not, from what I understand, I will need a new pump and/or shift servo? and pix/diagrams of what these are. Possible part numbers?

Howard Sterndrive · Jun 6, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

I'm not sure OMC(BRP) has sold any of those servo parts for decades. Around 1982, OMC started a program of replacing any failed hydromechanical lowers with full mechanical replacements (which also required electrical and mechanical mods to the engine and shift system). They basically abandoned support of that lower unit. Hopefully it's a helm cable or something simple.

Howard Sterndrive · Jun 6, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

just checked at shop.evinrude.com- they actually do stock some parts for the hydro lower- they still have the shift spool and valving, and the pump, quite a bit of the internals

anderso8623 · Jun 7, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

Well I disconnected the shift cables in the box. It is not the helm cable...BUT I do not think it is the lower unit either. I seem to be able to tug the lower wires just fine, although only about an inch. I assume that is all they move as the pully system in the box only has that much room in either direction. Could I just be expecting the world here and back then they where just hard to get in and out of gear and hard to find neutral?

anderso8623 · Jun 7, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

Also note, when the helm cable is disconnected, the shifter moves significantly easier then when connected.

Howard Sterndrive · Jun 7, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

shifting should be butter smooth in and out of gear when the engine is running. Did you check the gear oil in the lower unit? Water is the enemy of that hydro assist cylinder. If the oil is milky or water drains out before oil, that could be the cause.

anderso8623 · Jun 8, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

I will check the oil today. If it is milky, do I just drain, fill and be done or is there a bigger problem on my hands?

anderso8623 · Jun 8, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

Seems to be low on gear oil. The oil that was in there was a solid yellowish color.Is this the "milky" color you refer to? The problem I have is it is in the water. I know you are supposed to fill from the bottom, but do you have to? The screw at the top says "oil fill". I don't want to take this thing out unless i have to.

Boomyal · Jun 8, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

First of all there is no way you are going to drain, fill or top off the lower gearcase when it is in the water. Even the top plug in the lower gear case is going to be underwater and that top plug is only there to show when the lube level rises to that point.

Secondly, your milky color is undoubtedly from water intrusion. You need to pull the boat, drain the lower and pressure test it. Watch for air leaks around the prop shaft and the prop shaft carrier to outdrive case. If nothing shows up there, listen for air leakage between the upper and lower gear cases.

I just had that happen in my 78 hydro-mechanical unit. (water in the lower gear case) It turned out that my shift cable casing had a crack in it about 8" out from where the cable comes out of the shift housing on top of the lower gear case (well under water). I had to use an adhesive shrink wrap to re-case the cable.

Lastly, as the Hydro-Mech drive uses a pump to aid in shifting, there is a filter screen inside that I understand is prone to plugging up, starving the pump (that screen has been deleted on my drive). Long emulsified lube would form an insoluble curd that is likely to do just that. If that is the case on your unit, that would explain the difficult shifting.

And yes, the cables only move about an inch, either side of neutral.

Howard Sterndrive · Jun 8, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

I'm not sure how you are checking the lower unit in the water. If it is milky, low, empty, full of water or sand or metal- that will decide the next step. Gear oil is dark gold - like maple syrup.
Stringer drives are best stored out of the water - the uppers especially are prone to taking on water - not the best to moor a boat with that drive.

anderso8623 · Jun 8, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

I opened the "oil fill" bolt at the top of the out drive and it had a dip stick attached to it with a level indicator. When it was out of the water I looked for the gear oil vent, this was the only oil vent, other then the drain at the very bottom of the lower, on the entire out drive. I am used to outboards and know the one is usually right below the anti-ventalation plate. I did not notice that one when I looked it over.

Howard Sterndrive · Jun 8, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

the upper and lower are not connected on a stringer - they are 2 separate compartments

anderso8623 · Jun 8, 2013

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

Gotcha. I am determined to figure this out! I can not pull it till next weekend. I'll keep you informed. I appreciate all your help so far. Please keep checking this posting as I may not write anything till next weekend.

Tight shifting from neutral to forward or reverse, 1979 OMC 120

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