Switch Box Suggestions

[nokiddin]

Hi all.
I have an 84 Merc 90 2-stroke in line 6. I took it out for the first time this year last week. At home starting it in a tank, I was having some trouble, so I used some carb cleaner and sprayed it into the carbs while cranking and she fired up, idled and ran well with a bit more throttle too. Took it to the lake, had trouble starting. I initially figured it was a fuel leak, because I had a bad connection at the tank, which I fixed up, but still want starting so I used carb cleaner again, got it going, took it out, and couldn't get over probably mid range, but eventually it opened up, and ran normal. I wasn't too worried, since I have had this happen before when using up some gas from the year before. ( I know keeping the gas over winter isn't recommended, however with seafoam in it, it had seemed to be of little ill effect over the past several years). The boat ran well for that fishing excursion, but on the way home, died to barely anything. With full throttle, we were traveling 3 mph or so. Back at the dock, wouldn't start. I did start it with the carb cleaner again, but when trying to take it out, it ran slow like it did earlier and died in a minute or so. Haven't tried to start it since.

At this point I'll say, I realize the carb cleaner wasn't a good idea and will refrain from that in the future.

I got home and did some diagnostics.

I used a bore scope to check cylinders and didn't notice any big scores, pistons look good except for some carbon, heaviest on cylinder 5.
Compression cold with some 2 stroke oil squirted in the cylinders is 110-115 across the board. (Couldn't check cylinder 6). Also, the stator and trigger are good according to this page https://www.outboardignition.com/page39.asp. 2 trigger measurements were over 1300 ohms, in spec according to the page, but figured I'd mention it. Also, plug wires all measured about 0.6 to 0.8 ohms.

I found I have no spark on cylinders 1,3,5. Those all come from the top switch box. With the stator, trigger good, and plug wires consistent, I'm guessing something is wrong with that switch box. I should mention that I tried it with the kill switch wire off, and with the red/white and blue/white wires on it from the bottom switch box, and still no spark.
I am hoping you guys can tell me if I've satisfactorily isolated the problem.

Is there a way/worth it to test the switch box?

I see they are fairly pricey to buy from Merc or CDI..... Does any one know of any other less expensive parts out there? I see them on Amazon, and was thinking for a tenth of the price might be worth a try. Anyone have any experience with them?

Thanks for the help!

 

[Chris1956]

Sounds like dirty carbs to me, as she ran at high speed for you.

 

[Faztbullet]

Only use OEM, WSM, Serria or EMP switchboxes..The cheap Chinesem junk on Amazom can damage your engine. I have seen several posts on other sites where cheap boxes damaged motors

 

[nokiddin]

Thanks for the replies.

I assume finding used OEM switch boxes on eBay is a little risky as well as they may be due to go bad?

I was planning on going through the carbs and doing a link and sync. Do you guys have any specific recommendations on the settings for that? I understand using the originals isn't recommended with the new fuels.

Also, my back draft isn't plugged, should I do that?

 

[Faztbullet]

I assume finding used OEM switch boxes on eBay is a little risky as well as they may be due to go bad?

If seller can test and show bias circuit is good and box functions it might be worth a try. Might end up with one that dont work and no refund on used parts

 

[Chris1956]

Generally, ADI ignition timing on those IL6 motors was:

Idle pickup timing 0-9* ATDC
Max spark advance 21* BTDC.

On carbs, replace all gaskets and inlet needle and seat after cleaning. Check the floats for cracks, or just replace 'em.
Initial carb idle mixture setting was 1-1/2 turns open. Final idle mixture was set with the boat in the water, in gear and warmed up. Motor may bog at initial setting. If so, richen top carb mixture screw 1/8 turn open. Retest, if she still bogs, open mid carb 1/8 and retest, then bottom carb, testing after every mixture adjustment. You want smooth acceleration and an acceptable idle.

 

[nokiddin]

I found a local guy selling used, tested OEM switch boxes. I read that you should replace both together, but was wondering if this is still true if you aren't going to replace with a new unit?

 

[Faztbullet]

Yes replace both

 

[nola mike]

Hi all.
I have an 84 Merc 90 2-stroke in line 6. I took it out for the first time this year last week. At home starting it in a tank, I was having some trouble, so I used some carb cleaner and sprayed it into the carbs while cranking and she fired up, idled and ran well with a bit more throttle too. Took it to the lake, had trouble starting. I initially figured it was a fuel leak, because I had a bad connection at the tank, which I fixed up, but still want starting so I used carb cleaner again, got it going, took it out, and couldn't get over probably mid range, but eventually it opened up, and ran normal. I wasn't too worried, since I have had this happen before when using up some gas from the year before. ( I know keeping the gas over winter isn't recommended, however with seafoam in it, it had seemed to be of little ill effect over the past several years). The boat ran well for that fishing excursion, but on the way home, died to barely anything. With full throttle, we were traveling 3 mph or so. Back at the dock, wouldn't start. I did start it with the carb cleaner again, but when trying to take it out, it ran slow like it did earlier and died in a minute or so. Haven't tried to start it since.

At this point I'll say, I realize the carb cleaner wasn't a good idea and will refrain from that in the future.

I got home and did some diagnostics.

I used a bore scope to check cylinders and didn't notice any big scores, pistons look good except for some carbon, heaviest on cylinder 5.
Compression cold with some 2 stroke oil squirted in the cylinders is 110-115 across the board. (Couldn't check cylinder 6). Also, the stator and trigger are good according to this page https://www.outboardignition.com/page39.asp. 2 trigger measurements were over 1300 ohms, in spec according to the page, but figured I'd mention it. Also, plug wires all measured about 0.6 to 0.8 ohms.

I found I have no spark on cylinders 1,3,5. Those all come from the top switch box. With the stator, trigger good, and plug wires consistent, I'm guessing something is wrong with that switch box. I should mention that I tried it with the kill switch wire off, and with the red/white and blue/white wires on it from the bottom switch box, and still no spark.
I am hoping you guys can tell me if I've satisfactorily isolated the problem.

Is there a way/worth it to test the switch box?

I see they are fairly pricey to buy from Merc or CDI..... Does any one know of any other less expensive parts out there? I see them on Amazon, and was thinking for a tenth of the price might be worth a try. Anyone have any experience with them?

Thanks for the help!

Similar issue that I was chasing with a 25 hp all summer...Everything checked out with ohms testing, but voltage from the stator did not. I'd check voltages from everywhere before replacing the switch box.

 

[nokiddin]

Similar issue that I was chasing with a 25 hp all summer...Everything checked out with ohms testing, but voltage from the stator did not. I'd check voltages from everywhere before replacing the switch box.

Thanks for that info.

I have stuff on order to build a DVA adapter. In the meantime, what if I swapped the switch boxes (since I have two on this engine) to see if I get spark in those cylinders.

 

[nokiddin]

Was able build a DVA adapter and test things out further.

Blue wire to ground gave me only 18 V. Editing to add that I noticed that shaking the wires caused the blue voltage to get above 200 intermittently. Blue/white gave 400 V

All other measurements in spec.

So I gather from this that the stator is bad. Would this single abnormality cause the no spark on 3 cylinders when cranking? The cylinders affected area driven by the switch box where the blue wire attaches, so it would make sense, but I thought the blue wire was more for high range.

Should the yellow wires be detached from rectifier for testing?

Does it matter that my spark plugs are not in for the testing?