1970 Johnson 6hp Intermittent Shift Problem

[Sparkytech]

I have a weird issue that popped up today with my 1970 Johnson 6hp tiller. Shifting between forward, neutral, and reverse has worked flawlessly, until today. I put the motor on the boat, went to shift into reverse, and it was like the shift linkage was disconnected, and the lever moved way farther that it should. Moving it back and forth repeatedly, it seemed to “reconnect” and I was able to get it into gear. Whenever I shifted it out of gear, the same problem happened, and moving the shift lever repeatedly would finally get it in gear. After I got home, I put it on the stand, and it shifts just fine, and I tried it over and over again. I transport the motor on its side in the boat. Could that cause this issue, or should I tear into it?

 

[Pappy]

Your shift rod connector may have come loose for one.
You may have a broken shear pin as well. Pull your prop and check. Not sure whether or not the 1970 model is shear pin or spline driven props.
Edit - It is shear pin driven so check

 

[CedarRiverScooter]

There is a little plate on the side of the exhaust housing, 2 screws. Just take that off & the shift rod connection is right there.

 

[Sparkytech]

Thanks, I’ll check those things out. Does this make sense with the linkage connected / working one minute, and disconnected the next? I haven’t seen how this all connects mechanically yet.

 

[CedarRiverScooter]

If the screw is loose it can slip a little. Could be intermittent.

 

[Sparkytech]

I looked at my motor today, and there doesn’t appear to be a 2 screw plate on the exhaust housing. I did find pictures on the internet of this plate, but mine doesn’t have this. I took the boat out yesterday, same issues. Worked fine on the stand, intermittent on the boat. I have the motor and boat in storage right now, so I can’t send a picture, but it looked like there was a slight bulge / hairline crack from the inside out near the bottom of the exhaust housing. Max speed on my 14’ mod-v is only about 6.5 mph. I’m beginning to think this motor may be too expensive to deal with...

 

[Pappy]

..............and you never said that you pulled the prop and checked the shear pin. These pins can break and migrate one way or the other, sometimes catching between the prop hub and the propshaft and allowing the prop to work while the gearcase is in gear.
We don't write this stuff because we need finger exersize!
By the way if you do not have the plate/2 screw set up then the powerhead has to come off to do the job. Very easy to do.

 

[old_fart]

By the way if you do not have the plate/2 screw set up then the powerhead has to come off to do the job. Very easy to do.

I don't recall ever having to remove the powerhead to replace a water pump.
(you have to get at the shift linkage connector to drop the gearcase).
If there isn't an access plate, then the shift linkage connector can be accessed
through the gap between gearcase and tower-housing.

If the shift linkage connector is correctly installed, and the cap screw hasn't
come completely out, it should shift normally (the shift rod ends are relieved
so they are held captive by the cap screws in the shift linkage connector)

Check that the bellcrank (up on the shift handle you're using to shift the motor) hasn't
come loose. I don't recall that being a problem on that vintage motor, but that
was 40+ year ago (oops, I just dated myself again). The bellcrank is the part
that the top of the sift rod attaches to...

-W

 

[Pappy]

OLd Fart.......apparently you have never had to replace a water pump on a 5 1/2 then! Every one of them you have to remove the powerhead to replace the pump. Hence the suggestion that the powerhead may have to be removed.
I see the connector in the parts breakdown Also checked the manual and you are absolutely correct in that the gearcase has to be dropped like a 9.9 - 15 to expose the shift rod connector. Haven't done one in too long apparently!
Good suggestion on the bellcrank adjustment.

 

[old_fart]

OLd Fart.......apparently you have never had to replace a water pump on a 5 1/2 then! Every one of them you have to remove the powerhead to replace the pump. Hence the suggestion that the powerhead may have to be removed.
I see the connector in the parts breakdown Also checked the manual and you are absolutely correct in that the gearcase has to be dropped like a 9.9 - 15 to expose the shift rod connector. Haven't done one in too long apparently!
Good suggestion on the bellcrank adjustment.

Well, I'll admit to it being mannnnnnny year ago, in a previous life, but Iowa
man-made lakes had a 6HP limit in those days and there were a lot of them
6 & 5.5 motors around... When OMC let loose the 9.9/15 (around '74, I think)
a 6HP restrictor kit was quickly made available to allow the 9.9 to live on those
lakes (you could get the 9.9 with electric start).

I looked somewhere at the parts breakdown on that vintage motor motor, and looking
at the picture I'd want to agree with you, but I can't remember having to pop a powerhead...
On some motor of that vintage you could drop the gearcase and just barely get at the bottom
screw of the connector. The bottom shift linkage would have to be really short???

-W

 

[Sparkytech]

Thanks again for all of the suggestions here. I love the simplicity of older engines, etc.
Update: a full disassembly of the lower end found the linkage disconnected and signs of water in the gear lube. Now that I know how the linkage connects, it makes sense how it could be intermittent. The lower bolt on the linkage must have been loose enough, or a previous owner tried to force it to shift while stopped, and the shift rod pulled out. Easy fix! I think the linkage could have possibly “reconnected itself”, as the shift rod is held captive, and could technically be pushed back into the coupling / pop back out intermittently. The water pump impeller and lower end components looked good, cleaned out all the grunge from everything and sealed up / reassembled. If everything works well, and I’m confident now that it will, I’ll order new o-rings for everything. It looks like a previous owner used some sort of white residential grade caulk to seal it up. Some good quality RTV should keep it water tight for now.
The spot on the gearbox that looked cracked is near a really thick part of the casting. It may be nothing, and just a part of the casting, not sure.

 

[CedarRiverScooter]

Even though the impeller looks OK, I would put a new (OMC) one in, Rubber hardens with age & takes a set. It will be money well spent.

 

[Pappy]

In this forum we do not promote the use of any RTV when repairing engines.
Parts for that engine are super reasonable.
On the pump take a look at the lower wear plate and take a look at the pump housing where the impeller rides. If they are scratched up then get a complete pump kit. Always buy OEM as the parts fit (as opposed to other aftermarket parts) and the kits are complete.
On the gearcase the probable cause is the shift-rod O-ring. No matter how hard you try you will never seal that with silicone. It has to be replaced along with the "spagetti seal" and whatever else may be leaking.
So...............
Do it once and do it right!

 

[Sparkytech]

The gearbox seal looked pretty sketchy. As I mentioned, the RTV was a temporary fix to ensure the lower gearbox was totally sealed so I could test everything for function. The plan is to replace anything gasket or o-ring related as I disassemble / reassemble, and parts do seem inexpensive, so the water pump will likely be on my list. I just didn’t want to spend money and then find out there were larger issues that may not be worth the cost to repair. Tested it in the tank today and all seems to be functioning as normal again. Is there a particular vendor that anyone recommends for replacement parts?

 

[CedarRiverScooter]

I use marineenines.com They have a good website.