l have set max timing to 21 deg. as per manual. l have sync. cam to cam follower(is described in manual). Manual does not describe how to sync. throttle cam to timing(has an adjustable rod)!!!
Timing set at idle with timing rod disconnect from throttle and manual advanced to stop used timing light on #1 cyl. and adjusted stop to get 21 deg. My understanding is this engine has no mechanical advance like a car(or vacuam advance)so it should not matter rpm when set like this. Please advise if correct? Engine never revved over 1500 rpm.

How did u set the WOT timing? It has to be running in gear at full throttle in a test tank with a test wheel, or else it will be considerably retarded when u try to run it with a load on it.

If u were running it full throttle on muffs, u took a chance of experiencing ''thermal runaway''; without the backpressure on the underwater exhaust the engine is competely unloaded. Bits of burning carbon in the cylinders can preignite the fuel/air charge causing RPMs to race way beyond it is design capabililty; all u can do is disconnect the fuel & hope the carbs run dry before the motor literally tears itself apart.

There is a procedure for setting WOT timing at cranking speed, if u need it just ask. l guess u got the TDC timing pointer adjusted ok?

If you're talking about the throttle lever to cam rod, it should be 4 31/32 inches from center of the rod retaining nut on the lever to center of yoke pin on the cam.

l do not have the step-by-step to link & sync ur particular motor, but l can tell u that the cam must hit the roller right on the mark -- the roller retaining screw is mounted in a slot where it can be moved fore or aft. The throttle cable is adjusted via the trunion just inside the cowling -- set the cable to where neither the idle set screw nor wot stop screw r either so far in or so far out that there is no room for final adjustments later.

back pressure on the exhaust will lower RPMs, so add a couple hundred RPMs if setting the idle speed on muffs, & make final adjustment after u put the boat in the water.

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''My understanding is this engine has no mechanical advance ''

Just to be sure: 1980 johnson 60hp, right? model # J60ELCSR, 2-stroke, 2 cylinders, 2 carbs, electronic ignition?

When u said ''adjustable rod'' l thought u meant the lever-to-cam rod. the timing rod is not supposed to be adjustable -- it links the top of the throttle lever to the timer base -- that is ur mechanical spark advance. It rotates the timer base forward when the throttle is advanced.

Go to http://shop.evinrude.com click on ''Electronic parts catalogue select ''johnson'' in the drop down box, drill down to 1980/60hp then ur model #. Click on ''cylinder & crankcase''. #66 on the diagram is the spark advance rod -- fixed length, not adjustable. that bushing #62 connects with #64 on the ''ignition system'' diagram.

Manual calls for setting WOT timing as l described above; l never heard of doing it at 1500 RPM, but that does not mean it is wrong necessarily. Any case, here is how to set it without starting the engine:
Spark plugs out, throttle fully open, set the timer base under the flywheel tight against the rubber stop (wire it against that stop if necessary). Rig a spark tester with the gap set to 7/16''. Hook up the timing light to the #1 plug wire. Turn the engine over & set the spark advance to 17° BTDC. The engine gains 4º when it is actually running (vs. at cranking speed) - if u set it to 21º at cranking speed, the resulting pre-ignition will cause catastrophic failure for sure.

Back to ur original question: adjusting the roller to hit the mark on the throttle cam is what syncs the timing to the throttle valves. The spark advance must begin before the throttles start to open, else she will fall flat on her face when u try to accelerate.

Hope l am not confusing you.