1988 30HP Johnson Timing Question

S

STL808

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I?ve done some repair work on my 30HP and I want to check/adjust the timing. The Johnson manual say the timing shall be 30 degrees BTDC with a test wheel at 5400 RPM. The WOT range for my motor is 5200 ? 5800 RPM. Since I don?t have a test wheel I ran the boat on the water and my WOT with two people was around 5700 RPM. With the boat at 5400 RPM the timing was right on, but when I opened the motor to WOT, the timing was higher than the 30 degrees. So my question is should the timing be reduced to the 30 degrees at the higher RPM, or should I leave it as is. It seems to me that as the motor spins higher, the timing should be higher as well.

Thanks in advance for any help
 
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blimp

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Re: 1988 30HP Johnson Timing Question

There is an adjustable stop on the starter bracket just to the right of the carb (if looking rearward) that should stop the plate at 30 degrees for the last 1/3 of the throttle or so. It sounds like your linkage may be off a bit. I would try a "link 'n sync" to make sure the throttle advance is properly adjusted. The procedure is in the factory service manual.
 
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STL808

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Re: 1988 30HP Johnson Timing Question

Thanks. I did the link 'n sync already and I know what adjustable stop you are talking about. The reason I?m checking the timing is because I had to replace the bottom armature plate. The metal arm that connects between the armature plate and throttle assemble, where its connected to the armature, that hole was worn oblong causing about ?? free play in the assembly. I?m wondering since the timing was/is past the 30 degree BTDC that allowed the armature to ?move? on that pin and wear the hole instead of burning out my pistons? I don?t know if that makes sense or not because the parts guy never heard of the armature failing that way.
 
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blimp

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Re: 1988 30HP Johnson Timing Question

When the you move the throttle from 5400 rpms to WOT, do you see the armature plate moving at all? If so, you may need to adjust that bumper stop in a bit to reduce the WOT timing. The last 1/4 to 1/3 of the throttle movement should only affect the carb butterfly, not the timing.
 
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STL808

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Re: 1988 30HP Johnson Timing Question

Yes, the armature plate does move going from 5400 RPM to WOT. I'll back the bumper stop down ASAP. Thanks for your help.
 
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