No Spark

Fishstick

Seaman
Joined
Nov 2, 2008
Messages
56
1975 Evinrude 75HP (Mod# 75743S)

New to me old boat. Had the boat out four times and the first three trips I noticed that pulling out of the harbor in the morning when I went WOT, she would not plane. After the engine warmed a bit, the missing cylinder would kick in and she would run perfect for the rest of the day. This morning was a different story. I took her out and it did the same thing; however, it took a full 30 minutes of slow cruising, off, on before something kicked in and away she went running perfect. Pulled into a cove in a no wake zone, slowed her down and a couple of minutes at slow speed, I could feel a cylinder go dead again. Loaded her up and took her home. Pulled the plugs to check for fouling (None). Put an induction light on all plug wires and noticed bottom, middle good but zero spark on the top cylinder. Thinking perhaps the coil....

I'm no outboard mechanic, but I'm thinking if I switch out the top cylinder coil with the second, if the problem follows to the second and I have spark on the top then it's likely the coil.......correct?

Also pulled the harness covers and checked all the wiring and contacts. All were clean and tight with the exception of the (what I believe used to be red wire) off of the rectifier. Most of the insulation has cracked and fallen away from this wire. I've patched the wire and heat shrunk two layers over it. Put it back together and still no spark on the top.

I'll be ordering a new rectifier on Monday. Seems if that wire was complete toast, the engine would not run at all instead of the intermittent issue.

Any thoughts or recommendations???

Respectfully......Mark
 

Fishstick

Seaman
Joined
Nov 2, 2008
Messages
56
Re: No Spark

I should add that the motor was rebuilt last year according to the previous owner and I have the paperwork. Even on the two cylinders, it starts up no problems with a quick flick of the key. All the wires (with the exception of the rectifier) and contacts look new and no visible corrosion on the motor anywhere.
 

cougar1985

Lieutenant Junior Grade
Joined
Oct 7, 2005
Messages
1,023
Re: No Spark

if you switched the suspected bad coil to a differnt cylinder and the problem followed, it would only be logical that the said coil was bad.you are correct, no good can come from a burnt wire,cracked or a corroded one.
 

Fishstick

Seaman
Joined
Nov 2, 2008
Messages
56
Re: No Spark

Roger that. Thanks Cougar. Hopefully, I can isolate this to the coil and rectifier, we shall find out on monday when I try the coil switch. Much appreciated
 

Fishstick

Seaman
Joined
Nov 2, 2008
Messages
56
Re: (Update) No Spark top cyl

Re: (Update) No Spark top cyl

Switched out the coils and the problem DID NOT follow. Still no spark on the top cyl.

Any ideas on where to continue the hunt appreciated.....

Respects....Mark
 
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