1989 115 6cyl mercury firing only on 1, 3 and 5

[dawwgman]

stator ohm ok looks almost new
trigger ohm ok no sign of damage
rectifier checked ok
flywheel is good
timing is correct
change stator wires to switchboxes still only 1, 3 and 5 firing.
disconnected bias wire no change
Any suggestions will be appreciated. I'm thinking bad switch boxes.
This started with not getting over about 2000 rpms on the water and after about 5 min it suddenly went full speed and worked fine the rest of the day. Next time on the water it would only idle. any advance of the throttle it would stall and shut off

 

[roscoe]

Welcome to iboats.

Sounds like a switchbox.

You could swap the two switch boxes and check again.

 

[dawwgman]

Thanks roscoe I swapped the stator wire and the same cylinders were not firing. I'm going to swap both completely and try that. I'm try to understand how this ignition system works. Is this correct? The stator charges the capacitors and the trigger determine time when the capacitor releases the current to the coil. Does the stator have any set timing or just provide steady current

 

[The Force power]

The Stator provides a steady power supply to the switch-boxes.
Check the voltage output from the switch-box for cylinder 2 & 4; you should have 250-300 AC volts going to the coils
(make sure you have a full charged battery when cranking)

If you don't or have low AC voltage coming from the terminal(s) on the switch-box that feed power to the coil(s) #2 & #4 leads to a bad switch-box

If you have the necessary voltage coming from the Switch-box terminal, check the voltage on the other end of that wire connected to the spark plug coil (to check the wire also)
If no spark.... switch a working coil to that wire to verify if the coil is any good

keep us posted

forgot to mention....check the condition of the wiring & connectors, a lot of times they are the culprit

 

[jimmbo]

deleted

 

[dawwgman]

When all else fails listen to the people that know. I switched the switch boxes and the fire went to 2,4 and 6 from 1,3 and 5. Yea problem solved switch box bad. OK installed two new boxes and now no spark at all. So my hard head ordered a DVA meter as advised by the people that know. BTW I am a novice on outboard engines. I am a jackleg mechanic with experience on gasoline auto and big rig diesels. Thanks to all for the help. Love this engine it will scream when running right.

 

[jimmbo]

Recheck all your wiring. I will assume you took pictures of it before you swapped out the switch boxes.

 

[The Force power]

Also check the Ground-wires & connection, often Ground-wires are over looked/ignored but are equally as important!
have to tried it with the other to stator wires disconnected from the rectifier?

 

[dawwgman]

Question? red and blue wires from stator. Is this correct one wire provides current at low speed the other kicks in at higher rpm. Is this correct. If so which wire provides current at lower rpm? Reason I asked is for curiosity I checked the stator wires 1400 ohms on red wire and nothing on blue wire when they are connected to switch box. DVA meter should be here today maybe I can get to the problem.

 

[The Force power]

I looked in my manual at the 120 hp wiring my manual is my model# (90/120)
2 wires go to Rectifier the remaining go to Switch-boxes

Correct me if i misread your post;

I assume your motor is newer and has the Merc color wiring. when checking the Stator/wires they cannot be hooked to anything.(when taking an ohm-reading on the Stator-wires it checks the resistance on the coils & its wires)

 

[dawwgman]

OK got the DVA and checked current. trigger more than 4V on all wires. Stator blue was all over the place from no current to 170V. Red wire had correct current. New stator be here tomorrow. Question? can a bad stator cause a switch box to fail in like 5 min of testing. Also replaced the switch boxes back to the old one that were firing on 1,3 and 5 and they have no fire at all also. About ready to go to the bank and get a bucket of money and throw at it.

 

[The Force power]

Before you go and replace everything....visit the link on how to check certain components http://www.cdielectronics.com/wp-content/uploads/2016/05/Tech-Guide-Digital.pdf
this will give you a good understanding on diagnostics & will save you money "by just replacing"

 

[dawwgman]

Ok thanks for all the help. Got her running. After some thought when I switched stator wires from on switch box it did not change the cyl. firing. When I swapped switch boxes the fire changed from 1,3 and 5 to 2,4 and 6. New trigger now firing on all cyl. It is 30 yrs. old so I installed new switch box, stator and trigger. Awful feeling to be broke down 5 miles from boat ramp. The person I bought it from said the engine was only used maybe 15 times. Lets go fishing.

 

[dawwgman]

One other thing. When I removed the trigger I ran a magnet across the pickup on the trigger one was making fire and the other 2 was not. Curious if this would be a good way to check trigger.

 

[racerone]

You got one spark on that one or more than one spark ?

 

[The Force power]

Ok thanks for all the help. Got her running. After some thought when I switched stator wires from on switch box it did not change the cyl. firing.

The Stator-wires do not determine the firing-order; the trigger-wires do

"When I removed the trigger I ran a magnet across the pickup on the trigger one was making fire and the other 2 was not"

was this with the old trigger or new one?

 

[dawwgman]

racerone there is three places on the trigger to produce a current. Only one of the places produced a current. I'm kind of odd like to see how things work. I was using a magnet from a microwave that had much more power than the flywheel magnets. That made me think trigger was bad It is firing on all cylinders now. Decided to check compression it has 125 on every cyl. rebuilt carbs, set timing. checked all wiring, replaced trim relays, replaced water pump, replaced ignition switch. Just looking at this motor you would think it is only a few months old. everything is tight as new. Thanks for all the help on here.

 

[dawwgman]

Update it ran fine for like 5 min. then went beck to just firing on 1, 3 and 5. I disconnected the idle stabilizer and ran her for about an hr. in a tank and it runs fine. If you don't know you just keep researching. A blind hog fines and acorn occasionally.

 

[dawwgman]

Took boat to lake today. When prop engaged it would shut of advance timing and adjusted carb. fixed that runs great to about 3000 rpm then it starts missing advanced timing and retarded it change nothing. at half throttle it runs great. maybe carb. have picked up something or maybe the bad idle stabilizer damaged something. any ideas appreciated every thing on the ignition system is new.

 

[jimmbo]

Are you still getting spark to all cylinders at 3000 rpm? An Inductive timing light works well for that.
Are the floats set correctly on all the carbs? Is enough fuel getting to the carbs? Did you try spraying some gas-oil into each of the carbs to see if it made any difference?