Johnson Seahorse misbehaving

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afterpegassus

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Not wishing to hijack another thread on here regarding this engine, I have a 4 horse twin that has started to run mostly on one cylinder, then the second will cut in and out intermittently. Fuel system has been thoroughly cleaned out, so I tend to think the problem is electrical (not my strong point).
Any pointers greatfully received.
 
afterpegassus said:
Not wishing to hijack another thread on here regarding this engine, I have a 4 horse twin that has started to run mostly on one cylinder, then the second will cut in and out intermittently. Fuel system has been thoroughly cleaned out, so I tend to think the problem is electrical (not my strong point).
Any pointers greatfully received.
Click to expand...

You dont quote the model number so not possible to look up any details. depending on model it could be electronic or points ignition for example.

However I'd start with new plugs, check for two healthy sparks... best part of a cm from cdi a bit less from points.

Inspect/ check coils, if appropriate check, clean and reset points, plug leads. Identify the non firing cylinder by disconnecting plug leads on at a time.

Swapping parts from one cyl to the other can be useful for diagnosing problems.

Post the model number and can look up correct plugs if not known. Must not be resistive type if cdi. Gap will be 0.030"
 
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Thanks for that.
I will not be able to get to the engine until next Friday so will not be able to get the ID till then.
Is there a particular test for coil integrity or would swapping plug leads and checking spark be sufficient?
 
VicS said:
You dont quote the model number so not possible to look up any details.
Click to expand...

Model no. is J4BRCNR and Serial no. is B018704.

I was getting two fairly healthy sparks, but when I pulled things apart, I noticed faint cracks in the casing of one of the coils (the one for the cylinder with damp plug). Assuming this to be the problem, as a temporary repair, I've put a coating of Araldite on the casing but I guess I'll probably have to source another.
 
afterpegassus said:
Model no. is J4BRCNR and Serial no. is B018704.

I was getting two fairly healthy sparks, but when I pulled things apart, I noticed faint cracks in the casing of one of the coils (the one for the cylinder with damp plug). Assuming this to be the problem, as a temporary repair, I've put a coating of Araldite on the casing but I guess I'll probably have to source another.
Click to expand...

So its a 1982 model (CN=82), which is points ignition ?

Cracks in the coil almost certainly the trouble.

Mark or note the position of the old coil so that you can position the new one the same.

Quote that model number when you order a new coil . Not used in many models but should be available OK. $31 full price in US.
 
Just an update - the coil took a while to arrive from the States and whilst waiting, picked up on a mention of reed valves on a similar thread.
Stripping back the cover plate revealed one of the valves with a decent bit of jammed debris.
Debris cleared and new coil in place, she's running sweet as a nut now.
 
Thanks for the feed back.

Reed valves no often the cause of problems as far as I can make out but obviously not going to work properly with debris jammed in them.

These 4 hp twin Johnson/Evinrudes generally reckoned to be among the best of small outboards. Lets hope it now matches the reputation.
 
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