Topic: 1958 18 hp jhonson – Antique Outboard Motor Club,Inc

This topic has 13 replies, 6 voices, and was last updated 2 weeks, 6 days ago by crosbyman.

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December 2, 2025 at 10:12 pm #302018
james hobson
Participant
The throttle on my outboard jumped gear mesh so I took apart reset mesh on gears that turn magneto, set gear two teeth showing on each side of gear. When I open throttle to fast carb opens to 3/4 or can’t get to fully open horizontal no matter where gear mesh is set is this enough open for full throttle.?<!–more–>
December 3, 2025 at 6:16 am #302022
RICHARD A. WHITE
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Lifetime Member
The band is merely a guide…. it is not exact…. carb float opening, is set by adjusting the plate under the mag, if memory serves, so that the roller, hits the plate at the mark on top of the roller plate.

How was your timing set? Feelers gages or timing tool?

http://www.richardsoutboardtools.com
classicomctools@gmail.com

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james hobson
December 3, 2025 at 7:30 am #302023
crosbyman
Participant
Canada Member
Normally at START the roller should just touch the cam at the small bar.

Going full throttle, the cam will swing out and fully open the throttle plate at the rear of the carb.

do you have the manual… free download just print locally or store on your PC/laptop

https://www.socalaomci.com/library/johnson_service_manual_10th_edition.pdf

Joining AOMCI has priviledges 🙂
December 3, 2025 at 12:27 pm #302027
james hobson
Participant
Thanks i will check that out
December 3, 2025 at 12:28 pm #302028
james hobson
Participant
Thank you I will recheck to and adjust
December 3, 2025 at 12:29 pm #302029
james hobson
Participant
I use timing tool to set points
December 3, 2025 at 12:33 pm #302030
james hobson
Participant
Oh yes thanks for the manual I didn’t know or even thought they existed on line
December 3, 2025 at 12:49 pm #302031
David Bartlett
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US Member
Another thing to consider is the vertical link between the gears on the tiller and the magneto. I have seen one that was twisted and would not allow the mag to fully advance. Unlikely but easy to check.

David Bartlett
Pine Tree Boating Club Chapter

"I don't fully understand everything I know!"
December 3, 2025 at 5:19 pm #302036
seakaye12
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At the base of the vertical throttle connector….there is a “weak link” pin that engages with the gear assembly at the base. If that is damaged or sheared it will prevent the throttle from operating properly. #49 on the diagram.

If you haven’t already I would disconnect tne mag plate from the throttle at the “quick disconnect at the top of the throttle lever. It should be possible to see if the obstruction lies with the mag plate itself….or the twist grip and its parts.
December 3, 2025 at 6:06 pm #302039
labrador-guy
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Yes like seakaye says unhook the mag from the linkage. The teeth on the tiller handle should line up from full throttle to idle evenly. Is your roller that rides on the brass plate in good shape? Is the brass rod that goes from the carb to the roller the proper length? Sometimes the roller rod gets twisted causing throttle to not operate properly. The whole mechanism should move easily.

hope this helps

dale.
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