How do you perform a link and sync on a 1976 70 hp Johnson outboard?

Question

I just bought a 15' boat and it has a 70HP Johnson, and the ONLY way I can get it to take throttle and get it to plain out is to operate it from the throttle linkage at the carbs. I can use the fast idle lever on the controls and it starts and idles fine. I don't won't to put thoughts in any ones head but the only thing I can tell thats different about operating the throttle at the carbs. than at the controls is something to do with advancing the timing. Once I get it plained out and the throttle control operating the carbs. and not me, it runs all over the lake like nothings wrong. If you just try and accelerate it from the controls it just immediately bogs down right off idle.

Answer 1

you really need a manual for the step by step, but this should help:

When the throttle/shift control is advanced, 3 things happen.  The motor shifts into gear first;  second, the timer base starts its advance, then the throttle valves start to open.  It's critical that the spark advance begin before opening the throttles, else the motor loads up on fuel and falls flat on its face.

Here's a couple pics, the first is a scan from an early-70's manual, the second is a photo with more of the parts identified -- it's mid-80's motor but the parts are pretty much the same as yours.

http://i521.photobucket.com/albums/w333/...

http://i521.photobucket.com/albums/w333/...

first make sure the throttle lever & cam yoke are the specified 4 31/32 inches apart as in the first pic.  

Then take the airbox cover off and make sure that all three throttle butterfles are closed at idle and parallel thoughout their range of motion.  Adjust the WOT stop s***w if needed to be sure they end up perfectly horizontal (not beyond) at WOT.

Use the idle set s***w to set the idle at about 950 RPM with the motor idling in neutral (lower unit submerged).  Set it at around 1100 with the motor running on muffs -- backpressure on the underwater exhaust drops it by a couple hundred -- you have to fine-tune it at the lake.

There's a thumbwheel on the throttle cable just inside the cowling;  adjust to where the throttle lever moves between the Idle & WOT stop screws, with neither of those so far in, or so far out that there's no room for fine tuning.

You need to make sure that the motor shifts into gear *before* the throttle lever moves the timer base, which increases RPMs.

This is the crucial part:  the throttle cam has to hit the cam follower roller right on the mark.  You can see a s***w in a slot just below the roller -- that lets you move the roller forward or back to line it up with the mark on the cam.

The pickup timing should be checked with a timing light, you'd need a manual for how to do that, but if it's running good I'm sure it's ok.

That's a great motor, I have a '79 vintage on a 15' kingfisher.  Use only Champion QL77JC4 plugs gapped at .030, change your water pump impeller every couple years, change the gear oil annually, give it fresh 87 octane gasoline and don't forget the oil, it'll still be running after we're long gone.  I also add an ounce of seafoam per gallon of gas, keeps carbon from building up in the cylinders, keeps the carbs clean and keeps the fuel fresh.

Answer 2

five stars for jtexas