850 with no spark

[zrob90sc]

First post here guys

I picked up a 73 glastron with a 850 merc...I cannot get any spark out of it whatsoever. I have 12v at the red and white wires on the starter (right) side of the switchbox. However, on the distributer side of the switchbox i only have power on the brown wire...Absolutely nothing on the white wire. I tried tieing the brown and white wires together, and grounding black wire to get the coil to fire and but got nothing.

Do i have a bad switchbox? Can I jump the white wire on the right side of the switchbox to the white wire on the distributer and bypass the switchbox without hurting anything?

 

[Moody Blue]

Re: 850 with no spark

Don't jumper anything to the distrib side of the switchbox.

1) First thing to ask is does this boat have a kill switch? If so make sure it is enabled.

2) Disconnect the tilt limit switch if it has one. It may be defective. It is a small cylindrical device mounted to the switchbox mounting plate. It will have a single wire connecting to the (black?) terminal on the distributor side of the switchbox.

There is a good diagnostic here somewhere for the switchbox. The procedure will tell you if you have a bad switchbox or trigger assy. Do a search on this forum for "switchbox testing" or something similar.

 

[emckelvy]

Re: 850 with no spark

Here you go:

MERCURY BATTERY-POWERED CDI TEST FOR DISTRIBUTOR MODELS

This test is for the 332-2986 switchbox used from 1967-1978 on all the inlines.

This test assumes your coil is good (problems with CDI coils are rare).

DISCONNECT BATTERY

1. Turn off ignition;

2. Disconnect all 3 distributor wires on the Port side of the switchbox (and the ?mercury switch? if present);

3. Remove the HV lead from the ign coil to the center of the dist. cap (remember it unplugs from the coil and unscrews from the cap);

4. Reconnect the HV lead to the COIL only;

5. Position the free end of the HV lead approx. 3/8" from ground (block, shrouds etc), and find a way to hold it there;

6. Jumper the brown and white terminals on the dist. side of the switchbox to each other.

RECONNECT BATTERY

7. Check that you have +12V at the red terminal (even with the ign off);

8. Turn on ignition and verify +12V at the white terminal (same side as the red terminal);

9. Ground the black terminal on the distributor side of the switchbox - this should cause a spark each time you touch ground.

If you get spark with the distributor bypassed, and it won't fire with the distributor connected, the trigger is bad and the entire distributor housing assy must be replaced.

If you get no spark using the test, the switchbox is probably bad. In that case, be sure to check for correct power on the switchbox, check all connections, and check the coil's resistance to make sure it's OK.

HTH..........ed

 

[zrob90sc]

Re: 850 with no spark

Moody, I cannot find a kill switch located on the controls...the only thing i could find to that degree was the mercury switch which i removed and still no change.

Emc, I performed that test and got no spark at all at the coil.

Does anyone know how many ohms a good coil should have? Also is there anyway to test the trigger?

Thanks for the quick replies guys!

 

[emckelvy]

Re: 850 with no spark

No good way to test the trigger except by substitution into a known good, working system. The CDI tests can pinpoint a bad trigger but in your case, you've got no sparking when the trigger is bypassed. Likely the switchbox but still a process of elimination.

The coil is the least likely of the three to fail. Here's some tests from my manual:

"Disconnect coil POS and NEG and coil secondary wire prior to testing. The secondary wire is the wire to the distributor"

Resistance between the "pos"and "neg" terminals: "0" ohms. This would be between the green wire and black wire (aka the primary leads).

Between either primary lead and coil tower: 28,000-34,000 ohms.

If the coil passes resistance checks, very unlikely it's bad. My vote is for the switchbox!

HTH.........ed

 

[zrob90sc]

Re: 850 with no spark

Emc,

good info! i'll ohm out the coil tomorrow.


One more question, on the dist. side should there be continuity between the white and black wires?

Thanks.