Mercury 2Cycle 25 HP no spark

[pooka86]

Help, I have just encountered some type of ignition failure on my 1995 25 HP 2 cycle Mercury outboard 0G153788. I had just had the boat out of the water and did a water pump service, lower unit oil, and new plugs.<br /><br />Motor started up as usual took out on a slow cruise and 10 minutes into the ride at about 1/4 throttle the motor dies just like I hit the kill switch. No spark, no fire. <br /><br />So, this motor seems like a rather simple ignition system, however I have no idea on how to diagnose. I assume that the problem is either the Stator the Switch Box. I find it hard to believe that both coil's would fail at the same time.<br /><br />Any one have a simple diagnosis procedure for checking out and isolating the problem component?

 

[andy6374]

Re: Mercury 2Cycle 25 HP no spark

Since you have no spark (make sure this is the case by using a spark tester or someother method) you will need to test the trigger, stator, and switchbox. If you have a Seloc manual for your engine these tests will be easy. It amounts to testing the resistances between different trigger leads (for the trigger, mine should all read 1100-1400 ohms, I have an 88' V6 200hp merc so yours might be different) and testing the resistance between the the red and blue leads of the stator. You can't properly test the switchbox. So test the stator and trigger first and if those are fine, it's most likely your switchbox.<br /><br />Did you just charge or replace your battery recently. New batteries or improperly charged batteries can blowup a switchbox. Do the switchbox and stator have good grounds. A bad ground to the switchbox will certainly cause havoc.<br /><br />Hopefully someone else has the manual for your engine and can tell you the proper resistances.<br /><br />Hope this helps.<br />-andy

 

[andy6374]

Re: Mercury 2Cycle 25 HP no spark

P.S. Everyone should own a Seloc manual for their outboard. They are priceless and certainly they pay for themselves. I would highly recommend buying one if you are a 'do it yourselfer'

 

[ehenry]

Re: Mercury 2Cycle 25 HP no spark

Simple things first....make sure the kill switch just above the transom mount didnt somehow get flipped and cause it to die. Had that happen to me....felt real dumb when I found out what the prolem was.

 

[phorvati]

Re: Mercury 2Cycle 25 HP no spark

Definately check simple things first. Like using ohm meter check if theres a short across the kill switch. <br />I have a 9.9 2 cyl two stroke so it has very simmilar electrical items as yours. <br />On wednesday I started doing some research as to why theres no spark. We have CDI ignition that has Charge Coil(stator) and trigger coil. <br />They are located under the flywheel. Each of them has two wires going into the switch box. From the switch box there is a positive lead for each coil(2 coils) and one negative lead going to coil negatives. In my case charge coil was infinite ohms(it should be 700-800ohms) So I went to the store and bought a new one(109$) This one has 760ohms resistance across the terminals. So tonight I am putting the thing back together and I hope this was the problem. I had previously tested the spark and examined spark plugs, leads and the guy at the shop said that its unlikely that the coils are bad. Since they do not both go bad at the same time. You can also measure the resistance at the coils(.03-.05 ohms at the primary and something like 800ohms at the secondary)

 

[KIGuy52]

Re: Mercury 2Cycle 25 HP no spark

No spark at all could indicate a bad, or I should say, broken trigger. The small pickup module on mine broke completely off the plastic mounting ring yesterday. Hard to find those things too. Most places I checked will only repair your old one. BAM Marine's on-line catalog says they have them, but I won't know for sure until Monday.

 

[phorvati]

Re: Mercury 2Cycle 25 HP no spark

Update on my 9.9. I drove to a dealer and got the last charge coil(stator) they had. My old one showed infinite resistance. The new one showed around 400ohms. So I put it back in and it fired right up. I was warried that I might have to do the timing since I disassembled the flywheel, but apperently I didn't have to. I use my motor daily about and hour in seawater so it gets a lot of beating. after 3 years of such use this was the year when I had to replace a diaphragm on a fuel pump and stator, two pretty major items. Other than that it worked like a charm. Also, both items were pretty easy to replace after troubleshooting. Repair manual is a must.