Needle valves move during use on 1957 Johnson 10 hp

[DrummermanBob]

I completed a carb rebuild (among other things) on my 1957 Johnson 10hp. Used it for a week at the cabin last week and when i run it wide open, both of the mixture valves migrate and require constant repositioning. What provides tension on the valves to eliminate this movement? Is it the packing washers? Do I need to tighten the valve assembly to distort the packing washers? Is there something that can be applied to the valve threads? Motor runs great otherwise.

[Biddaddydan]

Hi,

The needles screw in brass tubes that protrude from the carburettor. Each of those has an hex-shaped portion which allows the tube to be tightened so the needle won’t migrate during operation or loosened so as to still permit the needle adjustment. Just don’t play too much with those as the packing could leak if disturbed too much.

There are no old outboards, just machines so well built, they have outlasted their owners !

• This reply was modified 2 years, 11 months ago by Biddaddydan.
• This reply was modified 2 years, 11 months ago by Biddaddydan.

[DrummermanBob]

So, is it the same hex that tightens the brass tube into the packing washers? I can’t see how that hex is adjustable independent of the seating on the packing washers or am I missing something?

[Biddaddydan]

That is exactly the point. Through screwing-in the brass tubes, the packing washers are squeezed against the needle which increase friction thus, immobilizing the needle.

There are no old outboards, just machines so well built, they have outlasted their owners !

[Biddaddydan]

And you are right, you will have to compensate for tube tightening by turning the needle the other way.

There are no old outboards, just machines so well built, they have outlasted their owners !

[DrummermanBob]

Thank you!

[reivertom]

One of my old motors did that, so I had to clean all of the old packing out and re-pack it before I could get a good tightening. The packing can get old, squashed or damaged over time.

[necks]

DrummermanBob, I had the same problem when I tuned up my 57 Johnson 10hp, after a while the needle valves started working loose, problem was, I used the old packing washers that were in there, mistake, removed the old packing washers. The older packing were getting stiff & hard, so when I tried tightening needle nut to keep needle in correct position, the older packing would still work out of adjustment, because of stiff packing. Went and ordered the correct packing #43-123, 4 per needle, 8 total, installed and went for another ride, adjusted needles, slowly tighten packing nuts so needles would stay in place, which didn’t take much. If it ever needs adjustment again, loosen up packing nut just enough to readjust carb, tighten packing nut just enough to hold needle in place without it vibrating out of adjustment. The moral of this story is use the correct packing and amount on each needle. Four washers on each needle I thought was too much, hard to disagree with OMC, but it works. Gene.

[Biddaddydan]

Necks, Just for the record, my QD-16 (1955) parts catalog shows 2 packing washers for each needle valve but then, the carburettor was slightly modified between those 2 models and their needle valves bear different parts numbers. This just underlines your point that one should inquire about the manufacturer’s specs for a given model / year AND abide by them for satisfactory results. Regards !

There are no old outboards, just machines so well built, they have outlasted their owners !

[DrummermanBob]

Thanks everyone for your replies. I think my problem is not enough packing. I also missed the use of the nylon washer to protect the packing. I will have to order some. Do they sell these separate from the carb kit?

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