merc 3.0 no spark

[jdejongh]

tyring to get her started for first time this year. Have a mercruiser 3.0 140 hp engine. No Spark,
tested coil and get good spark on high tension wire when i phiscally open and close points with screw driver. However when i test under normal cranking condtions , i dont get spark at high tension coil wire or spark plug wire. I checked to mmake sure the points open and close while cranking and the y do. i also notice that when i crank, the voltage att he coil drops from 12VDC to 9 VDC. any ideas would be appreciated

thank you

Jeff

 

[dubs283]

Re: merc 3.0 no spark

is your cranking test with the cap and rotor in place??

or are you checking for spark at the coil tower while cranking with the cap off?? (like when you manually open/close the points)

 

[Don S]

Re: merc 3.0 no spark

is your cranking test with the cap and rotor in place??

or are you checking for spark at the coil tower while cranking with the cap off?? (like when you manually open/close the points)

Doesn't matter, they don't do anything but distribute the spark from the coil to the different spark plugs.

Check your point gap, if the points don't open or close properly, they won't spark.

Also, check for power to the + terminal on the coil WHILE cranking.

 

[dubs283]

Re: merc 3.0 no spark

Doesn't matter, they don't do anything but distribute the spark from the coil to the different spark plugs

yep, but wanted to make sure he knew everything was working while cranking...now i re-read and see that in fact he notes points opening/closing while cranking

 

[Bt Doctur]

Re: merc 3.0 no spark

ok, did you actually open the points with an insulated tool? If not your screwdriver created the spark, not the points themselves.You can also use an ohmeter to verify "0" resistance with the points closed.
more than likely the points are oxidized.Nail file or fine sandpaper to test.

 

[jdejongh]

Re: merc 3.0 no spark

Thanks all for taking the time to comment.

Problem solved.

The points opened and closed ok but when i took them off to look at them there was a damn hole burned in the points. I replaced the points, set gap, timed and all is well.

however i do have a question. I replaced these points last season , what could cause them to burn up so quick? thank you

 

[Don S]

Re: merc 3.0 no spark

Did you replace the condenser? PS: the points do have a through hole in one side, but if you are referring to a large pit, that is usually caused by a bad condenser.

 

[jdejongh]

Re: merc 3.0 no spark

Yes don,
I replaced the condenser along with the points today. thank you..... Interesting you say this though, as i had a problem with the screw that holds the condensor in last year. the screw hole in the dstributer was stripped so the condensor moved around , i found the problem and tapped a new hole and new screw, but maybe when it was bouncing around in there last year this could have caused it.

 

[Bt Doctur]

Re: merc 3.0 no spark

The hole thru the lower contact is normal

 

[jdejongh]

Re: merc 3.0 no spark

yes points quit burned and pitted

 

[Bonnie Beldin]

Re: merc 3.0 no spark

I am new on this site..If you could; how do I post a question about my boast motor? In need of assistance
thanks Bonnie

 

[Bt Doctur]

Re: merc 3.0 no spark

main page, upper left, "Post New thread"