Merc PowerTrim 1150 -1975 inline 6 115hp - No fire on #6 only

I am a newbie to boats. Have 2 grandsons and want to take them fishing and such. I got this boat cheap, owner said it worked fine last year and wouldn;t fire this year. He put in new coil and plugs but had no electricity to coil. I am mechanical and my son is a mechanic; we bought it (we saw wire rot and didn't say anything to him hoping for a simple fix). I pulled all the wiring out and replaced/repaired all; internal and boatside harnesses, stator wires, etc. Put it all together, drained out all the old gas and started some voltage and other tests. Compression is 120 on 4 and 116 on 2 cylinders. 700 ohms on the stator during cranking. Stator is not shorted to ground. Have 12v on red and 12v on white w/ign sw on on the power pack
(332-2986A21). Plugs are brand new. Put an inline spark tester on and got spark on 1-5, no spark on 6. I need to test the plug wire tonight (started raining after spark test and had to get it under the tarp).

I want to run the powerpack test listed here but am thinking trigger since I have spark on everything EXCEPT #6. Is there a way to isolate no spark on one cylinder???


thx a lot (grandson waiting for the 4th of July)...

Re: Merc PowerTrim 1150 -1975 inline 6 115hp - No fire on #6 only

The spark plug wire should have a metal "wire" core. Pull the #6 wire and check continuity. At the distributor end the wire connection screws into the distirbutor cap so keep that in mind when you remove it.

Regards,
Inline6

Re: Merc PowerTrim 1150 -1975 inline 6 115hp - No fire on #6 only

Since that motor's year indicate it should have a dissy, you have only a single trigger and switchbox. if you have spark to one plug, you should have spark to all plugs. Check plug wire as was suggested. They corrode and can arc to ground as well.

The ign system is quite different than automotive ign. The coil is pulsed by SCR-controlled CDI switchbox, to produce spark. You might clean up dissy cap. Rotor is not removeable, and is $200 to replace, so don't break it.

Wires are avail from oldmercs.com or vintagemercs.com (I forget which). They are the yellow tiger tails for $6 each. They unscrew from dissy cap as was stated. Dissy Caps are $100+ so don't mess them up. Stator charges battery via a full wave bridge rectifier. You might check it for proper operation.

Re: Merc PowerTrim 1150 -1975 inline 6 115hp - No fire on #6 only

In addition to all the above suggestions, inspect the inside of the distrib cap. Maybe the terminal for #6 plug is damaged.

A quick test would be to swap plug wires (don't cross them, substitute them) and see if the problem is in the wire or distributor.

Re: Merc PowerTrim 1150 -1975 inline 6 115hp - No fire on #6 only

Thank you very much for your help. Got home yesterday and checked the #6 plug wire; had continuity. Struggled through the instructions for the two different power pack / switchbox tests, opened the dissy cleaned the rotor tip(chewed up a bit and scorching) and the contacts with a points file, did the tests and concluded that the switchbox was good.

There was an outboard mechanic I called two days ago to help me out since I don't know anything about outboards. He is the one that did the original spark check two days ago and said that #6 was bad and I needed a new switchbox. I called him after the switchbox test and told him. He said to replace the trigger because of the test and replace the switchbox since it was the original and might be marginal. Something he said in the conversation made me want to go back and do the spark test again since the switchbox passed. HINT: DON'T ASK THE WIFE TO HELP WITH THIS!!! MY EYEBALLS ARE STILL LIT @ 200 WATTS!!! Anyway, I have spark on all 6 holes.

Question now is how do I start this thing. I obviously need to get mix in the tank. There is a choke button on the dash, there is a manual choke on the motor, and there is a ??priming?? bulb inline with what appears to be the fuel line. Is it as simple as put the gas in and crank it??? (crank until the gas is pumped up?) I know I need a hose and water or trash can with water???

GIVE ME A 70 Corvette or 69 Mustang or 72 Torino or 67 GTO anyday......

Chris1956 said:

Since that motor's year indicate it should have a dissy, you have only a single trigger and switchbox. if you have spark to one plug, you should have spark to all plugs. Check plug wire as was suggested. They corrode and can arc to ground as well.

The ign system is quite different than automotive ign. The coil is pulsed by SCR-controlled CDI switchbox, to produce spark. You might clean up dissy cap. Rotor is not removeable, and is $200 to replace, so don't break it.

Wires are avail from oldmercs.com or vintagemercs.com (I forget which). They are the yellow tiger tails for $6 each. They unscrew from dissy cap as was stated. Dissy Caps are $100+ so don't mess them up. Stator charges battery via a full wave bridge rectifier. You might check it for proper operation.

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