40 hp Mercury switch box

[Newguy1988]

Hi everyone new user here. Does anyone know how to ohm test the switch box. The part number is 332-4911 I think it is the A8. It came off a 40 hp mercury marine serial number 5367818. That is all I know about the motor I just got it.

 

[gm280]

:welcome: aboard Newguy1988 to iboats. Glad you could join us...

There is a guide to test the trigger assembly and you can see that at this site;

tenkillermarine.com/mercreadings.asp

Seem different engines and models have different readings. So pick your setup out of the list and see what it should read. JMHO

 

[merc850]

5174089 thru 5556229 - 1979​

 

[Newguy1988]

Thank you gm280 and merc850. I tested the switch box and it is 4.36k. Much higher then it should be.

75-78

40(402)

332-4911

398-5255

750-1400 Note 5

180-220 HS 5800-7000 LS

4V+

20V+ HS 180V+ LS

180V

Note. 5) 2 cyl triggers read between the two trigger wires.
Now I have a new question. merc850 you said my motor is a 1979 but that box is for 1975-1978. Did the previous owner put the wrong box on? What switch box should I be looking to get?

 

[Newguy1988]

It just dawned on me that the ohm test I did was for the trigger assembly not the switch box. I think it is time to go back and retest everything. I have to see if I'm getting spark at either cylinder. I'll be back once I know more

 

[merc850]

I can't find any SWITCHBOX tests that don't need a Merc tester, the trigger test using a jumper will show a bad box too, use the "no spark or intermittent" paragraph

 

[Newguy1988]

No Title

I got a two books from the library specifically on Mercury outboards. I read up on my tests in one and decided to skim the other I'm glad I did. From what i found you test everything but the switch box. The tests are simple enough and when I get time to go to my dads to work on the boat more I'm going to test everything. Thanks for the help guys I appreciate the help. I will post what I find. I spelled switchbox wrong on purpose this time just for you merc850.

 

[merc850]

I only capitalized switchbox to mean the only the box test can't be done without the equipment, not that you spaced the word. If you follow the posted test procedure and there's no spark then the box or coil are no good; if it sparks the trigger is done.

 

[Newguy1988]

Ok I wasn't sure some people are real sticklers for spelling. I went to my dad's tonight and ohm tested the trigger and coils. Both coils tested bad I got a OL reading on both. There is a lot of oxidation in the coil tower and the plug wires are missing the metal ends that go into the coil tower. so I took them off and started playing with them. If I press the copper wire into the magnet just right and wiggle the voltmeter lead just right I get a reading. It actually test out good, so I am going to do some research on magnetic coils and see if I can repair them. My only concern is that the magnets are getting weak and I dont have the tool to test magnetic straith. So I'm going to see what they cost also and if they're cheap I'll get them and new plug wires. After that I can go onto further testing. I'll post the results.

 

[merc850]

I would buy new ones for security http://store.oldmercs.com/category_s/2040.htm

 

[Newguy1988]

Well I went and got a new switchbox put it on and it worked. For all of ten seconds, the motor died and the new switch box went out. That's what i get for buying a cheap off brand. Monday I get to deal with warrantying it . Don't buy ariel tek parts just a heads up.

 

[gm280]

Well I went and got a new switchbox put it on and it worked. For all of ten seconds, the motor died and the new switch box went out. That's what i get for buying a cheap off brand. Monday I get to deal with warrantying it . Don't buy ariel tek parts just a heads up.

First of all, how do you know the new switch box went out...again? And if you did verify it, then something else is causing your initial problems and the switch box is a results. So fix the initial problems before toasting another switch box. JMHO

 

[merc850]

If you are still using the old coils they could be damaging the SB, did you do the trigger test it could be the problem. Post some pics of the box and trigger I still don't know which setup you have.

 

[Newguy1988]

If you are still using the old coils they could be damaging the SB, did you do the trigger test it could be the problem. Post some pics of the box and trigger I still don't know which setup you have.

Yes I am still using the old coils. When I started reading on why the SB could have gone out again I read that a bad coil can send power back into the SB burning it out. I tested the trigger before and after buying the new SB and it is good. I'll post some pictures later if i keep this motor. Right now I'm about to quit on it, there is a 85HP on CL for $400. If I replace both coils and they don't warranty the SB I'll be putting another $410 into this motor I think it's no longer worth the work. But I don't know what I am doing right now I will post again if I keep working on it but for now I am done. Thank you merc850 for the help.