Spark to plugs

[mav6759]

Forgive me I am new to the outboard motor game. I have a question about Spark to the Plugs. Is there a situation where a motor can have enough spark to the plugs to start the motor but not operate the motor properly on the water. And had would gage if the plugs are receiving enough spark (if such a thing). What are some of the results of a motor not receiving enough spark.

Mav6759

 

[HighTrim]

Re: Spark to plugs

Weak or no spark will cause the engine to run rough, or simply not run at all.

Depending on the size of the motor, the spark should jump the gap on the inline spark tester a good 1/4" to 7/16" with a bright blue ZAP!!! Remove all plugs when testing, grounding out the leads not being tested to the block.

This is a sample of a cheap in line tester, available almost anywhere.



Also, the backpressure on the exhaust when the outboard is under load (on the water) is completely different from when on the "muffs" in your driveway. It will run differently, so you cannot be fooled by how an outboard runs when testing on muffs or in a barrel.

All sorts of different factors can produce a weak enough spark to not fire you motor, such as not enough RPM, poor ignition coils, defective Power Pack, Stator, etc...

 

[mav6759]

Re: Spark to plugs

Thank you very much for your reply, but please let me understand you correctly, A weak spark can cause a motor to preform correctly on muffs, but under pressure or under a load such as being on a lake can cause the motor to run rough, or not to run. Is that correct.

 

[rickdb1boat]

Re: Spark to plugs

Thank you very much for your reply, but please let me understand you correctly, A weak spark can cause a motor to preform correctly on muffs, but under pressure or under a load such as being on a lake can cause the motor to run rough, or not to run. Is that correct.

Absolutely...

 

[mav6759]

Re: Spark to plugs

How about compression, I have had two compression test done, one was 110, 90, 60. The other one was 110, 108, 109. Could a weak spart cause the very in the compression test ot through off the compression test.

 

[ezeke]

Re: Spark to plugs

To have consistent results you have to maintain the same test. If the engine slows down because the battery is weakening, you will get different results even from the same cylinder. You have to have all the plugs out to test one cylinder.