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Old 16-01-2017, 13:26   #1
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GM 20 20 THROTTLE SHIFT PROBLEM

I maintenanced my dual throttle shift units for my cat. Now, I can not get the throttles to stay in a good starting position. They spring back to almost idle and they don't want to stay in full throttle with the transmission engaged. I rerouted the cables so they are now at the smoothest and the bends are now a wide sweep. I lubricated all four cables. I synchronized rpm with throttle position. I can't seem to find a tensioner. Could it be the leaf spring on the top? This wheel and spring assembly is wet with oil. Any ideas?
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Old 16-01-2017, 14:42   #2
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Re: GM 20 20 THROTTLE SHIFT PROBLEM

That spring looks like its just for the detents, I don't think it would do anything for throttle tension. There are many jury rig ways to fix this, ranging from bungee cords to tightening a cable clamp around the cable sheath. Look at the governor end of the cable, if there's an external spring there maybe you can remove it. That might let the lever stay where you put it without putting back the friction you just removed. This problem is very common.
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Old 16-01-2017, 15:05   #3
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Re: GM 20 20 THROTTLE SHIFT PROBLEM

Is there a friction adjustment screw on the other side (the outside)?
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Old 16-01-2017, 17:59   #4
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Re: GM 20 20 THROTTLE SHIFT PROBLEM

Did you take before pics? Any bits left over?

You haven't engaged that top detent. That's a sign that your adjustment is out. I'm assuming these pics are not just a random setting.

What do you mean by you lubricated the cables? Morse cables should be dry. Oil will bind and pick up dirt creating wear. Grease is worse.

Some of the older style were soaked in a thin 5W oil then wiped drained and wiped before assembly. These look like the modern style with a teflon liner.

Grease or oil in the cables could be limiting travel. Easy to check. Just disconnect both ends and cycle them in and out.

Also ensure that full throttle is full throttle and not preloading the fuel pump lever.
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Old 17-01-2017, 13:13   #5
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Re: GM 20 20 THROTTLE SHIFT PROBLEM

I swapped out my twin lever throttle for a brand new single lever setup on my 2GM20 last year and I now have a similar problem, I have to jam a wooden wedge (spare thru-hull emergency plug) between the lever and the bulkhead to stop it creeping back to idle. Sorry if this doesn't answer your question but it looks as if this is a 'normal' problem with these type of throttle levers. If any one has a 'fix' for it I would love to know it!
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Old 17-01-2017, 13:16   #6
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Re: GM 20 20 THROTTLE SHIFT PROBLEM

Quote:
Originally Posted by Sailmonkey View Post
Is there a friction adjustment screw on the other side (the outside)?
No friction method. Thoroughly searched.
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Old 17-01-2017, 13:22   #7
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Re: GM 20 20 THROTTLE SHIFT PROBLEM

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Originally Posted by leftbrainstuff View Post
Did you take before pics? Any bits left over?

You haven't engaged that top detent. That's a sign that your adjustment is out. I'm assuming these pics are not just a random setting.

What do you mean by you lubricated the cables? Morse cables should be dry. Oil will bind and pick up dirt creating wear. Grease is worse.

Some of the older style were soaked in a thin 5W oil then wiped drained and wiped before assembly. These look like the modern style with a teflon liner.

Grease or oil in the cables could be limiting travel. Easy to check. Just disconnect both ends and cycle them in and out.

Also ensure that full throttle is full throttle and not preloading the fuel pump lever.
Yes, just a random setting as I was fiddling with it. I mean that the Yamaha manual specifically indicated to lube the cable. There is no limiting, just the opposite. The cables, for lack of a better term, are too free. I checked and the travel and adjustments are according to the Yanmar specs.
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Old 17-01-2017, 19:13   #8
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Re: GM 20 20 THROTTLE SHIFT PROBLEM

Let me start by saying I have no experience with this. Looking at your pics, it seems the leaf spring, by pushing against that little roller/pin, should provide friction against the detent plate it's pushing on. Is there any sort of adjustment under that small cover that holds the spring/pin in place? If the spring has lost tension, or a ridge developed in that brass-looking roller/pin where it rides against the detent plate, you'd lose some of the pressure which should provide the tension to hold the throttle position you set. Just a thought.
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Old 17-01-2017, 20:37   #9
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Re: GM 20 20 THROTTLE SHIFT PROBLEM

These guys are right, don't lube morse cables.
There will be a friction device, either a disc type, behind the center of the control lever, which involves tightening a (usually) large hollow nut that increases the frictional resistance. The other type is a "Band Brake" which will have a small adjustment screw, usually in behind the control lever when it is in the neutral position, which tightens the band around a small drum.
Either way, be careful, a little adjustment goes a long way.
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Old 17-01-2017, 22:35   #10
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Re: GM 20 20 THROTTLE SHIFT PROBLEM

Quote:
Originally Posted by captainwireman View Post
I maintenanced my dual throttle shift units for my cat. Now, I can not get the throttles to stay in a good starting position. They spring back to almost idle and they don't want to stay in full throttle with the transmission engaged. I rerouted the cables so they are now at the smoothest and the bends are now a wide sweep. I lubricated all four cables. I synchronized rpm with throttle position. I can't seem to find a tensioner. Could it be the leaf spring on the top? This wheel and spring assembly is wet with oil. Any ideas?


If you flipped the leaf springs, flip them back & dry contact areas, while checking for worn parts. Cable housing may be deteriorating, causing adjustment issues.
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