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1985 Mercury 50 hp cranks but won’t start

Ymaha05

New member
I’m new the the forum and boats for that matter. I have an engine that is cranking but not starting. Serial#6539688 I was told it’s not getting any spark. I tested the wires coming out of the stator and these were the reading I got idk the range that they should be in the two yellow wire we’re not connected to anything and just individually taped up
DCC339C8-0A7C-47F3-BBAE-EA09854F0A78.jpgF64ECF53-B155-467B-8307-5BEF29231BE1.jpgE424242D-5A04-47D4-B8FC-56BAA3F07D98.jpg
I also took reading from the trigger and they were as followed A36CEC8D-4907-473B-9879-0A1BCFEE8DA2.jpg66517E4E-9B9F-4E1E-9742-473C20EBC8D4.jpg
many help you guys can offer will be greatly appreciated. If anyone has the service manual in .pdf they could send me That would help also
 
I don’t think so. It’s an automotive meter
esi585k I got from amazon.
 

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Yeah; that won't tell you much. You can buy a DVA attachment for that on Amazon for about 30 bucks. THAT will tell you what's going on.

Jeff
 
I have an engine that is cranking but not starting. Serial#6539688 I was told it’s not getting any spark.

Have you actually tested the spark? Pull the plugs and test as this gives max cranking RPM. If still no spark remove the blk/yel wire from switchbox and retest.
 
I have a 1986 75hp with the same issues. Carb has been rebuilt and cleaned. Spark plugs have been changed. New gas. I had a repair guy come out and get it to start when he opened up the choke on the engine manually but I forgot how he did it. Can someone help guide me?

Thanks.
 
Have you actually tested the spark? Pull the plugs and test as this gives max cranking RPM. If still no spark remove the blk/yel wire from switchbox and retest.

I pulled the plugs and tested them against the motor. Like I do when I’m working on cars. No spark. What does the black/yellow go to/from?

I did did notice when I took the wires from the stator off to test them. The two yellow wires were dissconneted. To what I assume would go to the rectifier
 
The blk/yel is the kill wire from the key/dead man lanyard. Removing it takes them out of system...this leaks you stator,trigger and switchbox
 
The blk/yel is the kill wire from the key/dead man lanyard. Removing it takes them out of system...this leaks you stator,trigger and switchbox


Thanks! I’ll bypass the switch tomorrow and give it a shot!

I got a dva adapter. Does anyone have the page in the service manual I can use to test everything?
 
Cut the three wires going to the switch and connected them together. Still no spark.

My dva came I today, but I’ve never used one so I have no clear way to use it to test anything.
 
Why did you cut them????????????? All you had to do is remove nut and wire off switchbox. Connecting them together is the same as still connected.
 
Why did you cut them????????????? All you had to do is remove nut and wire off switchbox. Connecting them together is the same as still connected.


I tired that first and no change, so to eliminate the switch being the problem. I bypassed it by cutting it out and connecting the wires.
 
Connect the meter ground to the block. Hook the red wire to the blue and then the red stator wires. You should see at least 200 volts when cranking her over on the blue wire and at least 50 on the red.

Do that and report back.

Jeff
 
Connect the meter ground to the block. Hook the red wire to the blue and then the red stator wires. You should see at least 200 volts when cranking her over on the blue wire and at least 50 on the red.

Do that and report back.

Jeff


Thanks, I’ll try that when I get home today
 
Update: the ngk spark plugs and power pack I got off eBay came in today. Swapped them out and it fired right up. I’m not really trusting the power pack since it’s brand new and was $40 lol but it has a 90 day warranty. So I will probably buy a oem one.

Im still unsure why the yellow wires going to the rectifier were not installed and taped up. Is there a way I can test the rectifier and the yellow wires to make sure the stator is supplying power to the rectifier?
 
Connect them up to the rectifier, fire the motor up and check for AC voltage. You should see around 17 volts if the stator is okay. You should also see about 13-14 volts DC coming out of the rectifier if it too is working.

Jeff
 
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