Motor Problems 2 0f 4 not firing

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Northcal01

Recruit
Joined
Mar 25, 2012
Messages
3
Hello and thank you for your help,
I just bought a boat that has a 1992 Yamaha 115 motor, after cleaning up the boat I took it to our local lake and found it difficult to keep the motor running. Upon returning home I pulled the plugs and found that the two cylinders on the left side looked as if they not firing, they looked clean but had fuel on them, while the other two had a light tan color with no fuel residue. What would be the first steps in troubleshooting the problem?
Thank you Craig
 
9

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,874
Re: Motor Problems 2 0f 4 not firing

Test Compression and spark on all cylinders.
If good compression and bad spark on some, then test the inputs to CDI and outputs.
Service manual and proper testing equipment is a must
If compression and spark are good then it is probably fuel related.
too much fuel or not enough to fire properly
 
N

Northcal01

Recruit
Joined
Mar 25, 2012
Messages
3
Re: Motor Problems 2 0f 4 not firing

Thank you for your response, I was never considered a mechanic, could you provide me the steps on how to test for each of these possible solutions, what are CDI inputs and outputs. I know how to test for compression but you mention that I could be a fuel related issue, could it also stem for ?old gas??
 
9

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,874
Re: Motor Problems 2 0f 4 not firing

Old gas would effect all cylinders but trash/water can effect one or more carbs.
Like I said test what you can and read up on everything you can. Spark tester can be purchased at any auto part store, or use a timing light. Post back after you find out if you have good compression and spark
 
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