Other OMC mechanic's, shift dog replacement

[R.Johnson]

There has been a number of post's about replacing the shift dog, and forward gear after having an engine jumping in, and out of gear at WOT. Certainly if the dog, and gear show wear at the engagement surface, the rule is to replace both. On some engine's this call's for facing the dog in a certain direction. This post is not for the sake of argument, or speculation, just to point out what I have found. I have a 1976 35 HP in the shop with this problem. Forward gear look's fine, lug's on dog are rounded off to some extent, and service manual call's for the dog to be installed with the grooved, ( or ringed) end of dog to face the prop. Here is the question! Why? I used this dog as a check, simply because that is what was available. I set the dog up on a surface plate,( granite) using precision parallel's, and a Federal dial indicator held in a Nikon stage with 1-1/2 in. support beams. The tolerance I found is what I would expect with a mass produced part. There is no difference between front, and back. I have no way of checking the surface hardness, but as I would expect, it is more than file hard. As I work alone, and just for my self, my income is from labor, not parts. Why throw this $75 part away, when I can simply turn it around? One argument I have heard is that the dog will wear out if placed in the wrong direction. After doing this check, I would really like to see how if the shift linkage is set correctly. Most people on this board inquire how to do there own repairs, and save money. That is the purpose of this post.

 

[Joe Reeves]

Re: Other OMC mechanic's, shift dog replacement

OMC states that if that shifter dog is reversed, the engine will jump out of gear. I have no idea why but have assumed this is the case. Regardless of your measurements, I could only suggest that you install it backwards, then advise us of your findings. I'd be interested in the outcome.

 

[WillyBWright]

Re: Other OMC mechanic's, shift dog replacement

Typically both the faces round-off where they meet. The cogs on the shifter round-off and the cogs on the gear round-off. If you merely turn the shifter around, the rounded cogs on the forward gear now meet the lesser rounded faces on the former reverse cogs on the shifter and vice versa. While both forward and reverse may work fine for awhile, the wear over time would be accelerated due to the now unmatched wear. To do the job right, you have to change all of it. Since the cogs on the reverse gear wear far less, it's apparently acceptable to just worry about the forward gear. I'd expect that you'd go thru multiple sets of forward gear/shifters for before you'd match the amount of wear on the reverse.

 

[DHPMARINE]

Re: Other OMC mechanic's, shift dog replacement

Many OMC gearcase dogs are reversable.And are identical on both sides.So aren't the forward and reverse gears.When the manual states one way,it may also involve the angle of engagement as well as the depth.<br />Also,the engagement surfaces maybe totally different,3 lugs for forward,a stepped ramp type for reverse.<br />Another thought,clutch dog pin thru prop shaft may not be centered on the dog,changing the lenghth of the throw.(and depth of engagement)<br /><br />I hope this makes a good discussion.I enjoy it.<br />DHP

 

[R.Johnson]

Re: Other OMC mechanic's, shift dog replacement

I made this post for the sake of input, hope to here more. I have to take the grand kids for supper, will get back later for discussion. Joe! I agree, just would like a little more input.