Johnson Evinrude 90 HP (2001) misfires

dasf2008

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Dear Experts,

I have a Johnson Evinrude 90 hp year 2001 engine that was behaving badly mainly after warming up. I sent all the electronics to a specialist and the verdict was the stator. The spark coils were rebuilt.

After installing it, the main problem disappeared. But when revving above 3400 rpm, it would misfire from time to time. After reading quite a bit, I realized that it could be the CDI or the coils. I bought the CDI and the optical sensor from CDI electronics and two new sets of coils (original).

For my total sadness, after replacing it, it started to misfire again as I had replace nothing.

The first mechanic that I discussed told me that it should be the stator, as this rebuilding process is never perfect, and it might solve the problem temporarily, but it will come back later.

I contacted the guy who rebuilt, and he said his service would make it even better than the original. But he gave me two hints: It can be the flywheel or the cover of the optical sensor.

I am a physicist and though a theoretical one, I think If I understood the basics of how that sensor works, I could try to figure out what is going on myself.

For me, important information is that the misfire happens above 3400 RPMs and if I fix the rpm, like 4000 RPMs, it does not happen with a given frequency. It may run for one minute or two, then misfires, then after three minutes misfires again.

The engine is running smoothly when it does not misfire, has a perfect idle, carburetors were all done recently, spark plugs are new.

I live in Brazil, and the problem here is that the mechanics have very few tools. I see people talking about strobe lamps, etc. Unfortunately, they do not even know what that is.

They fix things basically by trial and error.

Could anyone help me? I will very much appreciate it.

In the attachment, is a picture of the engine's plate.

Thank you in advance for any hint!

Demetrio Filho
 

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racerone

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I would stop throwing parts at this motor , too expensive.-----And perhaps it is not an ignition miss.------Start with posting the compression values.----Use a timing light ( strobe light ) to see if it is an ignition miss.-----Drain the gear oil and look for metal bits on the magnets.-----I consider the gearcase to be weaker than earlier models V-4.-----It could be a gear issue !
 

McGR

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dasf2008

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I would stop throwing parts at this motor , too expensive.-----And perhaps it is not an ignition miss.------Start with posting the compression values.----Use a timing light ( strobe light ) to see if it is an ignition miss.-----Drain the gear oil and look for metal bits on the magnets.-----I consider the gearcase to be weaker than earlier models V-4.-----It could be a gear issue !
Thank you for your suggestion. I will check with my mechanics if we can get this strobe light. As far as the gear issue, do you think if the gears are bad it would do these skips? I wish I could represent well the hiccups but it looks like we switched on and of the engine very fast. This is why we believe it should be something electrical rather than mechanical.
Thank you!
Demetrio Filho
 

dasf2008

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How are the plug wires? Are they correct for this motor? OIS motors can experience noise issues if the wrong type wires are used. Also it is important to route the tan temp sensor wires as far away from plug wires as possible, again to mitigate ignition noise induced into the temp sense circuit.

There's some good information here too:
Thank you for your suggestions. The plug wires are brand new. It came with the CDI. I think the interference is a possibility. Would you kindly tell me how the temp sense circuit looks like? Are those cables that looks like they have a small cylinder? Then are kind of loose in the back of the engine.

Thank you!
Demetrio Filho
 

dasf2008

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Dear Experts,

One issue that was raised by the mechanics is that it could be the cover of the optical sensor that gives the sparking timing. He mentions that even light could cause issues. Do you think if this is the case we can identify the issue by simply inspecting such cover?
Thank you very much!
Demetrio Filho
 

McGR

Senior Chief Petty Officer
Joined
Jun 19, 2004
Messages
667
The tan wire shown is one of the temperature sensor wires.Capture.JPG
 
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are you 100% sure there is no water in the fuel? if there is and it has a canister type filter, they can get full of water, idle great but when fuel vacuum rises, it starts to "sip" water off the top with the fuel.
 
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