'99 Yamaha 75 hp two stroke, weak spark, won't start

justinduke

Cadet
Joined
Mar 19, 2012
Messages
9
I run the boat on a regular basis and ran it about a week ago, but now it won't start. I had some new plugs so went ahead and put them in (NGK B8HS-10), still not attempting to start. Used fire checker on all 3 plug wires and all 3 had some spark, but not a very bright spark.

I don't know much about outboards but I'm guessing the problem is in the CDI, stator or possibly bad ground/bare wire? Not really sure though. What do you guys think? How do I diagnose this?

I am about to order a service manual, but it will take a few days to arrive so any help would be appreciated, thanks!
 

justinduke

Cadet
Joined
Mar 19, 2012
Messages
9
Re: '99 Yamaha 75 hp two stroke, weak spark, won't start

By the way, I also sprayed starter fluid into all 3 carbs and it still didn't try to kick off.
 

SparkieBoat

Captain
Joined
Aug 17, 2009
Messages
3,643
Re: '99 Yamaha 75 hp two stroke, weak spark, won't start

stop spraying starter fluid in your engine..use mixed gas if you must. you need to test your CDI unit and stator and regulator.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: '99 Yamaha 75 hp two stroke, weak spark, won't start

Click on the links in Sparkie's signature for some troubleshooting help while you wait for your manual
 

pearse clark

Recruit
Joined
Jul 25, 2014
Messages
2
hi guys ,i am new to this forum and would like some please,i have 75 yamaha ceto and only have spark on cyliner 1 and 3, i have changed cdi unit and still have same prob, thanks pearse
 
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