1977 merc 115 IL6 no spark

phatmanmike

Captain
Joined
Oct 24, 2003
Messages
3,869
hi, i just had this motor running about 2 weeks ago, replaced the internal wire harness in engine and now no spark.. i have service manual, all wires are in the right place....<br /><br />im very new to mercs, if this were a omc id be done by now, any ideas... i am clueless where to start on this big merc<br /><br />m ikey
 

phatmanmike

Captain
Joined
Oct 24, 2003
Messages
3,869
Re: 1977 merc 115 IL6 no spark

update.. i did a search and found a lil info, not much though<br /><br />i DO have 12 volts going to the white wire on the brainbox/power pack thing(whats it called) when the key switch is ON. i check spark with a spark checker, manually and also with a timing light. with timing light on each plug wire... nothing<br /><br />with timing light on the coil wire... nothing.<br /><br />i also did this test, posted by clams canino..<br />
This test assumes your coil is good (most all are).<br /><br />DISCONNCT BATTERY <br /><br />1. Turn off ignion<br />2. Disconnect all 3 wires on the distributor side of the switchbox.<br />3. Remove the HV lead from the coil to the center cap (remember it unscrews<br />from cap)<br />4. Reconnect that HV center lead to the COIL side only.<br />5. Position that HV lead about about 3/8" from ground (block, shrouds etc)<br />and find a way to hold it there.<br />6. Jumber the brown and white terminals on the dist. side of the switchbox<br />together.<br /><br />RECONNECT BATTERRY<br /><br />7. Check that you have +12 V at red terminal.<br />8. Turn on ignition and verify +12V at white terminal (on red terminal side)<br />9. Touch the black terminal to ground - unit should cause spark each time<br />you touch ground.<br />
i did this test and it DID NOT SPARK when i touched the lead to the ground.. nothing... how can i check my coil?<br /><br />m ikey
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,468
Re: 1977 merc 115 IL6 no spark

PMM, Do you have 12Volts on the red wire, (next to the white wire) on the switch box? This wire should always be hot. <br /><br />To test coil use a voltmeter. Disconnect all the coil wires. Set meter to lowest ohm scale and zero needle. Test resistance across primary winding. Primary winding is where the two low voltage wires (green on right, black on left) attach to the coil. Reading should be 0-1 ohm (almost a dead short). Next check resistance between secondary winding (spark plug wire connection) to black wire (ground) terminal. Resistance range should be as specified in the repair manual. if it is infinite or low like the primary winding, the coil is bad. Coils are not too expensive ($30 )
 

phatmanmike

Captain
Joined
Oct 24, 2003
Messages
3,869
Re: 1977 merc 115 IL6 no spark

yes i have 12 volts on the red wire when the key is on... <br /><br />question, i tested my rectifier the way my clymer service manual stated and it failed 2 of the 3 tests. would a bad rectifier create this problem?<br /><br />EDIT: i just did the tests you described and when i test between the two smaller posts, everything is good 0.0 to 0.1 ohms....when i tested the continuity between the high tension lead an a good ground i got zero ohms! instant connection... si i guess im in the market for a new coil..thanks<br /><br />mike
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,468
Re: 1977 merc 115 IL6 no spark

PMM, It sounds like you have found the problem. Also, the rectifier would not have caused this problem on this motor. Since you need a new rectifier, i would check Radio Shack. I bought a 25 Amp full wave bridge rectifier from them for ~$4. It is superior in capacity to the OEM part, and has lasted me 20+ years so far. <br /><br />PS If you buy this part, the minus terminal on the rectifier needs to be grounded to the casing, and the ring terminals changed to female spade terminals.
 
Top