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72 50hp Evinrude...No Spark

bill_w

bill_w

Advanced Contributor
I finally got my Evinrude into the lake. You might remember I spent most of last year fixing an overheating/water circulation problem with this motor. Anyways, before I got it wet this year, I tried it in a tank, just to be sure all was OK. Nope. No start, checked the plugs, no spark. Last year it started fine, no troubles there. I did the head scratching, got out the books, and started checking things. I pulled the black wire off the number 4 terminal of the power pulse box, tried it again, still no spark. Hooking the wire back up, it sparked across the connection, with the key off. OK, thats not right. Tried it after tightening the connection, it started????

It seems to be an intermittent thing, but pulling the black wire off the terminal, and reconnecting it makes it run. Doing this once, the engine actually tried to start, I guess a plug sparked with the wet cylinder in just the right position.

This was all with the original Evinrude controls. To get rid of the push button gear shift, I swapped the remote control box with one from a 72 Johnson after I had it in the lake. The motor still has the intermittent no spark condition, that is fixed by disconnecting and reconnecting the #4 black wire. Running on the lake, it hasn't quit on me, but it did quit once at idle at the dock.

Any ideas? Could the pulse box be on it's way out? By changing out the entire wire harness for the remote, that should eliminate the key switch and anything in the wire harness.

One more thing. Its on a 15 ft runabout, tachs out at about 5200 rpm WOT, 30 mph on a GPS, with a 13 1/4 by 17 pitch prop. Do these sound like good numbers?

thanks in advance,
Bill
 

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Black and yellow is the wire for testing purposes !------Black yellow disconnected is the same as turning ignition to " on "------The controls both have a big yellow plug ?
 
When you say "black wire" do you by chance mean "black with white or yellow stripe"?

If so check to see if there is voltsge on that wire (engine off, key switch on and/or off).
 
Black wire...number 4 on the pulse box. According to the Seloc book I have, that is the ground wire coming from the ignition switch. And yes, both controls have the yellow plug connections. They are both from 1972 motors (one Johnson, one Evinrude) with the hydroelectric shift. I owned both.
 
OK..so where does the black/yellow wire come from? The ignition key switch, or the timer base? For that matter, where does the black wire I was disconnecting and reconnecting go to? Just a ground? If so, why did it cause the plug to fire when reconnected?

What should I do with the black and yellow wire? Disconnect it if there is a no start condition, and see what happens?
 
The black / yellow comes from the ignition switch ----------Disconnecting at the power pack is the same as turning ignition switch to " on "----------You are testing ignition switch and wiring in the harnes to the control.
 
OK..but since I have changed the whole harness and switch, and still have the same trouble, doesn't it make sense that the problem is somewhere else?
 
Test the trigger coils and test the charge coils.-----------Then if those are good , likely you have a faulty powerpack.----------------Always test before spending money !
 
It was acting up again this weekend. So, rather than go thru all the testing, I pulled the powerpack off my toasted '72 Johnson 50. Guess what, it works like a charm. It was the powerpack going bad.
 
The 1972 50hp factory service manual is a waste of money when it comes to the ignition system. The method described in it is obsloete, using obsolete equipment. Go to the CDI website for a better way.
 
Cheapest ive found is 142$. I plan to restore this engine completely bc its my first so eventually I will. But for today i want to troubleshoot the issue. Entire ignition system seems to be about 550. Anywhere cheaper than this site?
 
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