1958 35 hp Bigtwin Runs, But Stopped Moving!

[58CorrySuburban]

On my final run before winterizing: the motor started in one pull, idled nicely, and went into gear fine. As I was getting toward the end of the "No Wake" zone I noticed that the shift lever was popping out of forward gear but I held in gear for a second and it stayed. I made a few rounds in the cove there and it didn't do it again, so off we went. I slowed down to say something, and when I went to put back in gear it wouldn't engage. We were dead in the water.

We beached it and I tilted the motor up. With the motor off I put it into Forward and tried to turn the prop with my hand, it engaged (wouldn't move). Neutral - spun freely. Reverse - engaged again. I'm new to motors, and don't understand, how it could engage but not push the boat? I would think that whatever keeps it from moving when it is off would move it when its running.

Atleast I have all winter, and 2 parts motors to fix it...hopefully.

 

[HybridMX6]

Re: 1958 35 hp Bigtwin Runs, But Stopped Moving!

Bad prop or broken shear pin? Did you check the prop is good and the hub is ok, also check the shear pin under the prop. I'm assuming from the vintage you are talking that it has a shear pin under the prop. I had an old 1971 20hp Johnson that just loved to eat those things up. I always carried several spares for times just like that.

 

[jay_merrill]

Re: 1958 35 hp Bigtwin Runs, But Stopped Moving!

Sounds like a clutch dog gone south, to me.

 

[Joe Reeves]

Re: 1958 35 hp Bigtwin Runs, But Stopped Moving!

(Jumping Out Of Gear - Manual Type)
(J. Reeves)

This pertains to lower units on all OMC manual shift outboard engines, or any OMC engine with lower units defined as a Shift Assist or a Hydro Electric Shift unit which incorporates a "Shifter Clutch Dog".

Within the lower unit, splined to the prop shaft is what is most often referred to as a clutch dog, hereafter simply called dog. The dog has at least two lobes protruding from it on both ends, facing both forward and reverse gear. The forward and reverse gears also have lobes built into them near their center area. When the engine is running, in neutral, the gears are spinning constantly via the driveshaft being connected directly to the powerhead crankshaft, but the propeller does not turn due to the fact that the dog is centered between the two gears, and the dog lobes are not touching either of the gear lobes.

When the unit is put into either gear, shift linkages force the dog (and its lobes of course) to engage the lobes of the gear. The lobes of the spinning gear grab the lobes of the dog, and since the dog is splined to the prop shaft, the propeller turns.

The lobes of the dog and gears are precisely machined, most with right angled edges that could be installed in either direction, and some with angles slightly varied that must be installed in one direction only (one end only must face the propeller). Dogs that can be installed in one direction only, if reversed, even if the dog and both gears were new.... would jump out of gear almost immediately. Keep in mind that the lobes are precisely machined with sharp angles!

Due to improper adjustment or worn shift linkages, but usually due to improper slow shifting, those precisely machined sharp edges of the lobes become slightly rounded. Now, with those lobes rounded, as the rpms increase, the pressure of the gear lobes upon the dog lobes increases to a point whereas they are forced apart (jumping out of gear), and due (usually) to the shift cable keeping tension on the engines shift linkages..... the unit is forced back into gear giving one the sensation that the engine has hit something, and the cycle continues.

Some boaters with manual shift engines have the mistaken belief that shifting slowly is taking it easy on all of the shifting components..... Wrong! Shifting slowly allows those precisely machined sharp edges of the dog and gears to click, clank, bang, slam against each other many times before they are finally forced into alignment with each other..... and this is what rounds those edges off! The proper way to shift is to snap the unit into gear as quickly as possible.

 

[1946Zephyr]

Re: 1958 35 hp Bigtwin Runs, But Stopped Moving!

It sounds like your linkage is out of adjustment, or worn. If there is any slop in the shift mechanisms, or if out of adjustment, then it won't operate right. Shift linkage out of adjustment, is a very common issue with these and leads people to think the gears are shot. That happens a lot too, but checking the integrity of the shift linkage is a good place to start. A lot of JohnyRudes have the shift linkage bolted to a bell crank, which is on the inside end of the shifter. These will often be a problem.

I had a customer come to me, because his was doing this same thing. He tore down his lower unit, thinking it would save money. Well, after nicely puting the lower unit back together, I found that the upper shift rod was sloppy. I pulled the powerhead off and found that the retaining bolt for the upper rod had worked loose. After I tightened it up, everything shifted normally again.

Leon

 

[58CorrySuburban]

Re: 1958 35 hp Bigtwin Runs, But Stopped Moving!

I didn't check the shear pin before because when (with the motor off) Placing the shift lever into the Forward position - the prop wouldn't move. Neutral - spun freely. Reverse - didn't move. I thought the prop would have spun freely even when in gear. I checked it and the pin is in place.

I drained the lower unit and found water. My brother-in-law had bought seriously thick gear oil (made for busses, and semis). I noticed in the Seloc manual that it says not to use automotive gear oil, because it bubbles and outboards can't compinsate for that. I went along with it because he has much more experience, and has successfully helped me trouble shoot before. Could the oil have been the problem?

 

[Joe Reeves]

Re: 1958 35 hp Bigtwin Runs, But Stopped Moving!

Lack of oil could have caused internal gearcase damage, and if so, the replacement of oil now will not cure the problem.

 

[58CorrySuburban]

Re: 1958 35 hp Bigtwin Runs, But Stopped Moving!

So it does not mater that (motor off) in both forward and reverse the prop wont turn by hand? Not that I would know, but would this seem to indicate that it is engaging, and the cylinder presure is preventing me from turning the prop?

 

[tmcalavy]

Re: 1958 35 hp Bigtwin Runs, But Stopped Moving!

Compression will make it hard to turn the prop forward or reverse when in gear, but you should be able to budge it...just be careful with the prop blade. I would drop the lower unit and check it out...see if it will turn (prop) in gear with the driveshaft dropped down out of the crank (powerhead). If not, you may have a problem in the gearcase.

 

[rolmops]

Re: 1958 35 hp Bigtwin Runs, But Stopped Moving!

There is special lower unit gear oil that you can buy at walmart and every outboard store and marinas.It is roughly the stuff that your brother was aiming for (90 weight hyphoid oil).
As for the shifting problem:
If you have a remote control,disconnect it and see if it properly shifts at the side of the engine.If that is the case,your remote control needs to be adjusted.
If the problem persist at the side as well.It can be one of 3 things.
A:The handle needs to be adjusted and tightened.
B: The bell crank is sloppy.This is a bit involved because you will have to take of the power head to get to that pesky little screw.
C:Your clutch dog is shot or one of the pins is loose.
A is a good possibility and an easy fix.B is likely the cause and although it is involved,it is not hard to do.C is the least likely,but it is more of a pain in the neck to do.

Just remember.These engines are simple and you do not need to be a rocket scientist to fix them.

 

[58CorrySuburban]

Re: 1958 35 hp Bigtwin Runs, But Stopped Moving!

I checked for "play" in the shifting rods by putting a flathead screwdriver into the seem of the shift rod connector. The shifting rods moved precisely with the shift lever. So, I'm guessing that eliminates a bell crank problem.

I'll have to remove the lower unit. I have already dissasembled and reassembled one from a parts motor, just so I knew what I was getting into, and to make sure I could get it back together.

Thanks again,
-Josh

 

[58CorrySuburban]

Re: 1958 35 hp Bigtwin Runs, But Stopped Moving!

Hey Guys,

I just wanted to update this thread with the conclusion so that when someone else runs into the problem, and searches it on the internet, there is some finality (though it could have been any number of your suggestions).

In my case it was...(drum roll) the pinion gear (symbol crash)! When I took the lower gear housing off and pulled the gears I saw it, totaly worn down except maybe 1/16 th of an inch toward the top of the teeth. Thats why it spun, but barely, and only under very little load.

I just popped open a parts motor and switched it out. It did lead to another question, but I should post it in a new thread.

Thanks again for everyone's time and input,
-Josh

 

[jay_merrill]

Re: 1958 35 hp Bigtwin Runs, But Stopped Moving!

Good post. That's not an issue that I've seen or heard of before, so I feel like I learned something.

Glad to hear that your are "back in business!"