1980 70hp Johnson throttle sync procedure

[xc600]

Is there a cut and dry link and sync procedure for a 1980 70hp Johnson engine?
I'm mainly concerned with the way the throttle interacts with the timing advance mechanism.
All three carbs work off the same rod so I can assume they stay in sync, but what about sync-ing the throttle to timing advance?
I've done a bunch of reading the last few days on all the related subjects here and just can't pinpoint what my problem might be.
Here's the lowdown:
1980 70hp Johnson
Idles fine, will idle in gear, falls on face when throttle is advanced much past just placing it in gear and engine stalls.
Carbs have been cleaned (really cleaned, and blown out, I've owned two strokes all my life and can clean a snowmobile carb blindfolded), spark plugs new and gapped correctly, fresh fuel, fresh fuel line.
I know at one time this idle on this engine has been played with and I'm wondering if the throttle rod length has also been changed. Is there a measurement for that?
I'm wondering if someone could break down steps to take in order to follow up on this when I see the motor next, i.e. compression test, spark test, spark lead removal test, etc?
And yes, I read the "sticky" at the top of the forum, it just doesn't go into that type of detail. I've done a lot of what it recommends.
Thanks for reading.

 

[tashasdaddy]

Re: 1980 70hp Johnson throttle sync procedure

the reason the TOP SECRET FILE does not go into link n sinc, is that it is different for most motors, year and HP. You need the OEM service manual for your particular motor for the linc n sinc procedures.

 

[xc600]

Re: 1980 70hp Johnson throttle sync procedure

Are the factory manuals available on-line anywhere? Can you download certain sections if they are?
I already have a Seloc manual, the motor came with it. I'd hate to buy another manual for just one section of it.
Alan

 

[capnstabbin]

Re: 1980 70hp Johnson throttle sync procedure

Look on ebay for your service manual, they cost 15 to 30 bucks, well worth the money. Theres plenty of good stuff in those manuals

 

[jtexas]

Re: 1980 70hp Johnson throttle sync procedure

OEM service manual available at marineengine.com or outboardbooks.com -- you need that section today, you'll need another section tomorrow. I have that seloc manual, it's ok for some stuff, but confusing if not just plain wrong for others. the factrory manual is well worth the cost, has saved me literally $thousands.

Couple things I know of that'll cause that...idle speed set too low, and throttle valves opening too soon.

Idle speed should be around 850-900 in gear in the water, set it to around 1000-1100 on the muffs then fine tune after you launch.

refer to the pic below (ignore the yellow arrow). Notice the throttle rod has to be 4 31/32 inches from throttle lever to yoke.

The idle set screw has to be butted up against the throttle lever; adjust cable length using the black thumbwheel.

The throttle cam has to hit the roller right on the mark. Adjust the roller if neccessary.

If you adjust the roller, go back & make sure the throttles still get to a horizontal position, and not beyond, at WOT. The WOT stop screw is just above the idle set screw; looks just like it.