7.5 merc spark problem

S

sleddhead1

Recruit
Joined
Aug 7, 2008
Messages
1
my 7.5 will start up and run fine for about 5-10 mins. and then shuts down.I have no spark for about 20mins. then same runs-stops. the wiring to the kill switch is burnt ,also motor is electric start, ser# is 4402963, I believe it's a 76
any ideas.........
Thanks mike
 
Last edited:
JB

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: 7.5 merc spark problem

Howdy, Sleddhead1.

Welcome to iboats. :)

My guess is that you have a heat related failure in the ignition system somewhere.

Need the year to say any more.
 
MrGED05

MrGED05

Seaman
Joined
Jul 25, 2008
Messages
50
Re: 7.5 merc spark problem

Sir,
When you've an idle moment, you might wish to check and insure that your engine has NO air leaks in the intake or gas lines. The small Mercury engines are famous for running for a bit then quitting because they have an air leak somewhere. Not a matter of spark, just a loss of vacuum in the fuel supply line.
Gary
 
A

allymoss

Petty Officer 2nd Class
Joined
Feb 3, 2007
Messages
163
Re: 7.5 merc spark problem

if it is actually your spark going, then I think it is probably the coil. Because the wires inside are so thin, when they heat up they can be distorted if they are old and corroded. I suggest removing the coil and make sure it is not touching the engine and run it then as it wont heat up as much.

Check fuel lines etc aswell
 
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