1979 Johnson 140 weird timing issue on port side when warm

[jioe4]

Hi guys, I really hope someone can help with this.

My 140 will start up ok and takes a few minutes to warm up enough so I can back it off to idle (following tests done with motor on earmuffs in my driveway). At first the idle is ok, but after a few more minutes the idle gets really rough and then every 10-20 seconds cylinder #4 (port side bottom) makes a pop and sends a puff of smoke out the side of the engine. I put a timing light on when it is doing this, and see that cylinders #4 is firing at the correct time sometimes, but also is pretty regularly firing 180 degrees off! Timing on other cylinders is ok. Also when it is running, if I pull the spark plug wires one at a time, #4 is the only one which doesn't make any difference. Finally, when I shut down after doing this test, the flywheel is quite a bit hotter than the rest of the engine (rest of engine warm to touch, flywheel hard to touch). There is no binding of the timer base that I can see, nor any obvious external damage to it. However it is obviously pretty old.

Obviously I suspect a timing problem. I have done all of the ignition tests including CDA measurements in the manual, and the timer base is generating a healthy voltage (~1.2volts) on both sides. The magnets on the flywheel are not loose or obviously damaged. I have already replaced both power packs, no difference made. Am getting healthy sparks everywhere (just at the wrong time!) Is it possible that the timer base is making some sort of intermittent contact when warm, and screwing up the timing on the port side? Should I spring for a new one, or is there some other test someone can think of to do to make sure (I am nervous after having already bought the power packs to no avail).

Thanks a lot.

 

[jbjennings]

Re: 1979 Johnson 140 weird timing issue on port side when warm

I would switch the coil from #4 to the other side and see if the problem follows the coil. I don't see how the timer base could possibly be a problem for just one cylinder---then again......
When you say the timer base is screwing up the timing on the port side, I get confused. You also said that #4 was the only one giving you trouble, not number 3. If number 3 is o.k., and the only problem is #4, then the coil for number 4 is at fault or you've got a bad plug wire or otherwise shorting on wire number 4. Maybe a bad spark plug?
I'm sure you've already swapped coils to see if the problem followed the coil, but if not, that's what I'd do.
JBJ

 

[jioe4]

Re: 1979 Johnson 140 weird timing issue on port side when warm

Thanks a lot for the quick answer JBJ. Sorry that was confusing, the reason I suspect port side timing is because I also see intermittent timing-suspicious problems (backfiring and confirmed with timing light) on the top port cylinder (that is #2, no??), but that is much less often than the bottom port cylinder which is firing 180 degrees off almost all the time after warmup. Before I started suspecting timing I switched the coil from #4 around to other cylinders, the problem did not follow the coil.

I know you must all be thinking I must have wires switched somewhere, so am I and I have checked over and over. I am down to thinking about the timer base since it has separate coils and leads for the port and starboard side, and I could sort of imagine the wires inside maybe making improper contact only when hot. But I have seen no mention of this problem on these forums before, and don't want to waste $200 to find out. All of the coil resistances on timer and stator are within manual spec.

Is it unusual/bad for the flywheel to be a lot hotter than the engine? I have a reasonably healthy pee hole flow, but did not investigate thermostats yet.

Also, is backfiring (not really backfiring but periodically sort of blowing smoke out the side of #2 and #4) something anyone has heard of and a useful hint?

 

[emdsapmgr]

Re: 1979 Johnson 140 weird timing issue on port side when warm

Your engine has two identical power packs, one controlling each head. You can test them by swapping them, then determine if the misfire problem moved to the other head. If so, it's a pack problem. That would be an easy solution. Odd ignition problems can occur when the components heat up to normal operating temps.