Re: '77 Merc 115 Loses Spark
ok. firediver....you need to find out if this is a power supply prob or a trigger prob......the switch box mounted in front of the carbs..on the 4 terminal side you should have 12v on the red terminal ALL the time....on the white terminal you have 12v when the key is turned on...next time this thing doesnt start get out your trusty 12v test light and make sure you have power on BOTH those terminals...if you dont you have a harness connector thats corroded up or wiring/key switch probs..all relatively easy to fix......if you have power on those 2 terminals and no spark,you will need some fancy test equipment to verify what has failed....but if your a bettin man, go with this...these coils almost never fail, switch boxes do, but when they do they fail completely and dont come back....now, 95% of the time you have a no spark situation is because of the trigger failing...classic failure is good first start of the day and after heat build up will fail...the trigger in these units is the distributor housing itself...you have to pull the distributor off the motor and do a complete teardown,assemble correctly and retime the engine...not a job for a rookie.....for your sake i hope its one of the former probs and not the latter.....
