1974 Johnson 25hp [25RL74M] Throttle Adjustment

[Bevo2000]

Hello everyone,

I have searched everywhere but unable to find a step-by-step guide to set the carb throttle to original factory specs for my motor (1974 Johnson 25hp [25RL74M]). After installing the Ignition Tune-Up Kit (0172523) and the Carburetor Kit (0396701), I thought this was a piece of cake, but this is not the case. What's interesting is that even the service manual I have does not cover this topic in any great details (it does have a few sentences for simple linkage adjustments, but not enough to set to factory specs).

I have attached some pictures containing the idle adjustment, throttle linkage and the flywheel roller that I have been tinkering with but the the issue remains: I am unable to open the throttle fully from the tiller handle. I have been working on this for a couple of months now and can't wait to test it in the lake. This is the last step so PLEASE help if your manual has this information or that you know how to do this.

Thanks in advance.

 

[racerone]

At the base of the towershaft are the gears timed properly ??

 

[tomhath]

This might be obvious, but do you have it in forward gear? It won't open all the way in neutral or reverse.

 

[anthill]

The omc service manual is $15 on ebay.

 

[Bevo2000]

At the base of the towershaft are the gears timed properly ??

I will remove the handle and reinstall just to make sure. Thanks

 

[Bevo2000]

This might be obvious, but do you have it in forward gear? It won't open all the way in neutral or reverse.

Thanks for the suggestion. I just tried but no luck.

 

[Bevo2000]

The omc service manual is $15 on ebay.

I got mine from ebay as well and thought it was a “factory “ service manual, but I think it lacks a lot of details for a beginner.

 

[anthill]

I agree, the manual assumes we know more than I do, but my 73 manual has a good description of the throttle cam follower adjustment. Is there more to it than that?

 

[Bevo2000]

anthill I have attached the same section from my manual. The problem I had was what position should the throttle control on the handle be in when the cam follower is between the two marks on the throttle cam? Slow, Start, Shift or Fast? I followed the instructions and the throttle wouldn’t even open when I turned the handle. This is when I cam here for help. Thanks again everyone.

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[racerone]

The slow / fast thingy on the handle is only a crude guide.-----The stuff in the red lined info is for adjusting / synchronizing throttle and spark advance.----Maximum throttle is merely checking that all linkages are attached and fully rotating the magneto plate.

 

[Bevo2000]

The slow / fast thingy on the handle is only a crude guide.-----The stuff in the red lined info is for adjusting / synchronizing throttle and spark advance.----Maximum throttle is merely checking that all linkages are attached and fully rotating the magneto plate.

Thanks. Are you saying that it doesn’t matter if the throttle is opened or not when I turn the handle as long as the linkage is attached and the throttle cam/magneto plate rotates?

 

[racerone]

Throttle plate MUST OPEN at the correct time.----For starting you just rotate the magneto plate to the neutral stop.-----Throttle will open to full when motor is in gear if all linkages are correct.----So easy to confirm in my opinion.

 

[Bevo2000]

Throttle plate MUST OPEN at the correct time.----For starting you just rotate the magneto plate to the neutral stop.-----Throttle will open to full when motor is in gear if all linkages are correct.----So easy to confirm in my opinion.

Yes it’s easy for a pro like yourself Do you mind showing with some pictures?

 

[racerone]

Sorry----Fixing motors is easy.----Posting pictures is not something that I want or need to learn.

 

[oldboat1]

The plastic screw you have circled is the idle stop screw (throttle, not carb). First step would be to back out the screw all the way, then see where you are.

The current setting may be the lowest adjustment at which the motor will idle at the moment -- which may mean some cleaning or fine tuning (e.g., carb issues).

 

[Bevo2000]

oldboat1 Thanks. I appreciate instructions like this because if I know what I was supposed to do, then I wouldn’t be asking. If I were giving instructions, I would assume that the other person is a beginner. Otherwise, I wouldn’t bother responding at all.

 

[Bevo2000]

Admin, please close/delete this thread for me. Thanks

 

[54bobby]

you might have something binding up somewhere. pull the tiller twist grip and check for old solidified grease inside or possibly a broken friction block inside the handle. once that old grease firms up it can mimic a mechanical problem but in fact, just need a good cleaning and new lubricant.

 

[racerone]

Just take the motor to a shop.----Ask them to show you how to operate a motor.-----Or buy a new one where all you have to do is " push a button " to start it.----Sorry if you can not figure out how your motor works.------Over and out.

 

[Bevo2000]

Just take the motor to a shop.----Ask them to show you how to operate a motor.-----Or buy a new one where all you have to do is " push a button " to start it.----Sorry if you can not figure out how your motor works.------Over and out.

Please do me a favor and don’t respond to any of my posts in the future. That would be really helpful. And thanks to everyone else for giving your advice.