Merc 402 NO SPARK

Bought this a month ago, started it up in a garbage can full of water. So after I replaced the impeller, + leg oil which were fine. Then again restarted it again in a garbage can, all seemed fine. So took it to lake and launched it for first time and would not start. Brought it home and when gas squirted in cylinder it fired, so changed the gas pump diaphram + check valves, and put in carb kit. Now after getting it back together yesterday I have no spark.
After reading in the forums I seen to remove salmon (orange) wire from the switch box to see if spark returns (which it didn't) and to check if voltage was present on this salmon wire with key on ( which there isn't.) My question is what would be the correct sequence to trouble shoot backwards to find my problem. One other thing I noticed is that the little box called the rectifier with 2 yellow wires leading to it from the stator is looking like it has been very hot sometime before I bought this boat and with all the moving to get to the carb one wire is a little loose but the holding nut is rusted on and unwilling to tighten as it wants to turn the bolt inside the rectifier. This rectifier looked this way before when I started the motor in the garage but now the one wire is a tad loose.
Any help would be appreciated as the nearest dealer is 80 miles away and $80 bucks a hour.

Re: Merc 402 NO SPARK

check to see if you have a saftey kill switch that the clip fell off of. maybe on the shifter sometimes. you can unhook the harness from the engine and see if it has spark when you turn it over at that point

Re: Merc 402 NO SPARK

Maxz695 said:

check to see if you have a saftey kill switch that the clip fell off of. maybe on the shifter sometimes. you can unhook the harness from the engine and see if it has spark when you turn it over at that point

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It has no kill switch at controls, + you mean to unplug the harness at the motor and to turn engine with the rope recoil and to check for spark?

Re: Merc 402 NO SPARK

aceallenk said:

It has no kill switch at controls, + you mean to unplug the harness at the motor and to turn engine with the rope recoil and to check for spark?

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I disconnected the harness and turned it over, no spark!

Re: Merc 402 NO SPARK

get an ohm meter and check the stator yellow to yellow should peg the meter at 1K Ohm setting and the blue and red should be under 2 and show improvement whenslighly turning the engine

Re: Merc 402 NO SPARK

Maxz695 said:

get an ohm meter and check the stator yellow to yellow should peg the meter at 1K Ohm setting and the blue and red should be under 2 and show improvement whenslighly turning the engine

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I have a meter set on 1K Ohm and when I connect it to the two yellow wires at the rectifier the meter jumps up, as it also does when contacting the blue and red on the switch box. I will have to wait till the girlfriend drops over to see if there is any increase when turning motor over at the (yellow + yellow) and at the (red + blue) as I'm unable to check this without a third hand. I also want to thank you for your assistance, I very much appreciate it and will get back to you in about 2 hours. If you have any other choirs in the mean time feel free to coach.

Re: Merc 402 NO SPARK

aceallenk said:

I have a meter set on 1K Ohm and when I connect it to the two yellow wires at the rectifier the meter jumps up, as it also does when contacting the blue and red on the switch box. I will have to wait till the girlfriend drops over to see if there is any increase when turning motor over at the (yellow + yellow) and at the (red + blue) as I'm unable to check this without a third hand. I also want to thank you for your assistance, I very much appreciate it and will get back to you in about 2 hours. If you have any other choirs in the mean time feel free to coach.

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Girlfriend dropped over and turned over motor and there was an increase on the Ohm meter when checking the red and blue configuration. Never seen any difference with the yellow + yellow when engine turned over.

Re: Merc 402 NO SPARK

is the yellow to yellow going all the way to the other side to 0 andis the red and blue with in 0 to 2? if so stator is ok. check wiring disconnect any wires leading to salmon these are kill wires. One goes to the tilt switch on the motor and the other to the ignition kill. Also remove the grey tach wire connected to the yellow and try that without it connected. Make sure all grounds ar tight coil rectifier starter solenoid. What do the wires on the switchbox look like are they good or corroded?Usually if the switchbox is going bad 1 cylinder would usually still fire on a 2 cyl 2 on a 4 cyl if non are firingandnothingeles worked i,m leaning towards the trigger

Re: Merc 402 NO SPARK

The yellow to yellow will go all the way to the end when a connect to the wires themselves, but as I first stated these 2 yellow wires connect to the rectifier which has gotten previously very hot and somewhat cooked the wires and the connection poles, they are very rusty and unable to tighten one of the yellow wires which is a quite loose. I'm unable to loosen or tighten as the one connection pole appears it wants to spin inside. I did spray some WD 40 on those last night and perhaps I could try to get that nut moving now. When I make contact with the Red + Blue my Ohm meter shows 3 (a radio shack model, cheappy which Ive had for many years) and when the motor is turned over (electric start) it goes to the end of meter as well. Could you tell me what that rectifier is for, and perhaps I could cut the one loose yellow, solder a little more wire and another fitting and nut up to the rusted nut..

Re: Merc 402 NO SPARK

aceallenk said:

The yellow to yellow will go all the way to the end when a connect to the wires themselves, but as I first stated these 2 yellow wires connect to the rectifier which has gotten previously very hot and somewhat cooked the wires and the connection poles, they are very rusty and unable to tighten one of the yellow wires which is a quite loose. I'm unable to loosen or tighten as the one connection pole appears it wants to spin inside. I did spray some WD 40 on those last night and perhaps I could try to get that nut moving now. When I make contact with the Red + Blue my Ohm meter shows 3 (a radio shack model, cheappy which Ive had for many years) and when the motor is turned over (electric start) it goes to the end of meter as well. Could you tell me what that rectifier is for, and perhaps I could cut the one loose yellow, solder a little more wire and another fitting and nut up to the rusted nut..

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I found the name of the rectifier from a post with my motor wireing diagram, and the item that has the rusted poles is called the rectifier from that wireing diagram. Heres the link to that diagram, http://www.maxrules.com/oldmercs/Wiring/1966ona/24.pdf

Re: Merc 402 NO SPARK

Re nutted the yellow wire at the rectifier, did another Ohm test using the tips of the poles and meter shot to the end, I assume this helped this loose connection, still no spark.
I disconnected the orange wire at switch box, no spark at either of the spark plugs. My question now is what is the trigger you refer to,

Re: Merc 402 NO SPARK

the rectifier turns ac current into DC current and it,s mostly for your charging system. The trigger is the unit below the stator. The crankshaft turns and at a certain point the trigger sends a singnal to the swichbox wich then sends intermiten signals to the coils inthe right firing order.Being that your stator seems to be sending the current to the switchbox I would think it is iether the trigger or the switchbox. I don,t know the tests for these they should be in a manual if you have one or try to get the info off a manual you can get in the first post of the mucury section of the forum called FAQ go there and see what you can find under electrical system troubleshooting

Re: Merc 402 NO SPARK

Maxz695 said:

the rectifier turns ac current into DC current and it,s mostly for your charging system. The trigger is the unit below the stator. The crankshaft turns and at a certain point the trigger sends a singnal to the swichbox wich then sends intermiten signals to the coils inthe right firing order.Being that your stator seems to be sending the current to the switchbox I would think it is iether the trigger or the switchbox. I don,t know the tests for these they should be in a manual if you have one or try to get the info off a manual you can get in the first post of the mucury section of the forum called FAQ go there and see what you can find under electrical system troubleshooting

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Thank You Very much for your time and help Maxz695. Your a true Gentleman.