mercury 1979 40 hp electrical problem

[soso40]

I have this 40 horse Merc and it will run 1.5 miles with no problem. Then it dies. It won't start. There is no spark at the spark plug. I wait an hour and it will start again but won't rev up. So I drift all the way back to the boat ramp, put the boat on the trailer and it runs fine. Please help.
Thanks. soso40

 

[valdano]

Re: mercury 1979 40 hp electrical problem

i have the same problem. my 97 40 hp.mercury die on the water .after 4,5 h. start with no problem. and happen this all over again,and again.i thing maybe we have bed sparks on the ignition cables or bed coiles.but im not sure.

 

[jimmyzshack]

Re: mercury 1979 40 hp electrical problem

My 1983 25 hp is doing this. i can make a high speed run for a while but when i go to idle it will die and not start up again for a while. I bought a spark plug tester and the light looks weak to me compared to my lawnmower. i tested the stator resistance from the book and it failed it. I have a new stator coming in tomorrow i'll post if it fixed my problem. If i can get this flywheel off to put it in.

my book for your '79 40 says resistance between yellow and ground rx100=15-20
between yellow and white coil wires should be rx100=7.5-10