No spark with spark plugs in

[Underdog Garage]

I’m new to this site and hope someone could help me. I’m having trouble with a 1993 evinrude 40 hp on my pontoon boat. I took it out over the weekend and it seemed to run great for the majority of the day. When I was getting ready to leave it wouldn’t start. Primed it and nothing. Checked bubble and it was hard. Finally tried fast idle and it acted like it wanted to start. This went on for a while until I was able to get a tow in. After checking a lot of stuff I’ve come to the conclusion that I’m not getting spark with the plugs in. If I take them out they will spark. Both the plug grounded alone and with a spark tester. Question is what would cause such a thing. If I use fast idle it will try to start but in neutral nothing. I’m leaning towards the timer base but any info or suggestions would be appreciated

 

[flyingscott]

Does spark jump a 7/16" gap? What is your compression?

 

[boobie]

Bad battery or battery connections.

 

[Underdog Garage]

I’m getting good blue spark on both plugs when out of the cylinder and grounded to the head. Battery is fully charged and turns over great. As far as a 7/16 gap goes I will have to check. I’ve done a lot of diagnoses thus far and as I said will not fire when plugs are installed. I read on a CDI website that was a symptom of a faulty timer base but it they referred to it as an “open” timer base which I have no clue what that means.

 

[Underdog Garage]

Sorry. Compression is 125 and 140.

 

[Faztbullet]

If it will jump a 7/16 air gap spark is to weak to bridge gap under compresion. If the case usually a bad stator or pack but need DVA to test.

 

[jakedaawg]

Weak spark is not a timer base issue...that's what you are describing.

as suggested, obtain the appropriate tester. Steven's instruments company makes very good affordable spark testers that let's you see both cylinders at same time.

then follow the step by step guide at cdi if you want. Do not skip any steps. Guessing will cost way more than a spark tester, dvom, and peak reading voltmeter.

 

[racerone]

Slow cranking ( plugs in ) means no spark.----Charge the battery / load test the battery.-----Inspect battery cables.----Take starter apart for inspection / ohm test from commutator to shaft , possibly new brushes.----Not much money spent doing the testing !!

 

[Underdog Garage]

Thanks for the reply. I will definitely test before replacing. Motor turns over great. Question is why will it hit and try to start with fast idle in a sweet spot but nothing when in neutral position? .

 

[Livewire7316]

im having the same problem with my 1975 85hp, great spark with plugs out.....nothing with them in.
Did you figure it out? Im thinking its my battery because the guy I bought it from just has a car battery in it,