Clutch dog slip, on a Scott?

[billw]

At the Shelton meet, yesterday, I ran two different Scott Atwater 16s: A 1956 and a 1958. Both ran really well. However, the ’58 had what very, VERY much appeared to be a jumping clutch dog…at low speeds only, like just off idle. It would go fine, no problems at all, getting up on plane and running at WOT. The ’56 had no such problem. I had the ’56 gear case apart, previously, and was somewhat impressed with it; as it was a four-ramp clutch with a bit of undercut, much like a Merc. Is the ’58 gear case somehow different? I don’t really get how it could do this jumping quite a bit at off-idle but be fine throughout the rest of the RPM range, where a bad OMC clutch dog would be at its worst.

I do not think it was lean-spit. If it was, it shook the entire boat and motor like no lean spit I have ever seen…..

See, I told you that I get more weird problems than most….

Long live American manufacturing!

[frankr]

The ’58 has the dog on the drive shaft, as you mentioned. And worn out ones are so rare, I can barely remember even having one apart. I’m wondering if maybe a linkage problem isn’t putting it in gear all the way, and when under power it latches up the rest of the way. Just a wild guess.

[garry-in-michigan]

It seems to me Scott used a spring in the prop shaft to push the clutch dogs forward and hold it against the gear selector cam. If weakened by rust, it could cause sloppy shifting. Ware in the shift shaft and shift rod bushings could also be a factor. Needless to say it should not be run while jumping out of gear.

[frankr]

Yer right, Garry, but wrong year and model. Here is a typical 16hp Scott (1957)

post a picture

[jim-moffatt]

I am not sure what is going on but the Scott dogs through 56 had the ramp you are talking about but its purpose may have been to let the propeller free wheel on deceleration. All my Scotts do this, you can hear the clicking when you back off from full power. Maybe if the idle power pulses are far enough apart something like this is going on.

[frankr]

Jim, the "undercut" or whatever the proper word is, that Bill & I suggested may not even be true. But we were not talking about the obvious ramps. We meant the 90 degree faces may have just a couple of degrees reverse taper so they tend to latch together under pressure. Like I said, I don’t know if they are made that way or not. There must be some reason they are so durable, especially considering the funky shift linkage design. Besides that, they are rotating faster when shifting than a dog on the prop shaft does. Shouldn’t work at all, but they do.

[jim-moffatt]

I agree Frank. My final thought is that the dog is held engaged only by the flimsy detent behind the shift lever plus any undercut. If the detent isnt positioned properly front-to-rear or not bent out to produce enough spring pressure the detent wont work properly.

As an aside I have had about 6 of this style shift and all worked fine.

[jim-moffatt]

One last gasp!

IF the shift rod isnt adjusted properly for up and down movement, the shift lever wont be vertical in neutral. You should check this. Misadjustment of the shift rod in the leg housing cannot be fixed by adjusting the detent leaf or spring position. The rod is adjusted by screwing it in and out of the fork that operates the shift dog.

[billw]

Thanks, all. I will look and see if the handle is absolutely straight. I did my’56 gear case a couple of years ago, so I forget: I believe one would have to pull the power head to adjust shift…is that right?

Long live American manufacturing!

[jim-moffatt]

You drop the leg from underneath it. Remove the reverse lock ring and loosen the lower pivot clamp screw then remove the 10 bolts holding the leg on. Drop the leg down and off. Leave the power head supported by the clamp.

[Author]

Posts