Re: 86 175hp merc lost spark
Before you buy parts check the outputs from the Stator and trigger using either a Peak ranging DC multimeter or a Scope (if you know someone that has one). You can check these at the switchboxes. (called power pack above. Procedure ,I believe, is in factory manual. Might save you a load of money on parts you don't need. I had similar problems and it turned out to be a bad outer switchbox, which dropped the spark to cyls 4 and 6 until motor and therefore switchbox got warm. On mine , with a cold engine there was no spark but you could warm the switchbox up with a hair dryer for a few minutes and the spark would come back. You would also be getting an oil alarm if you lost the output to no 4 cyl coil from switchbox ,as this is compared to oil pump shaft motion sensor...if the two don't match alarm goes off. Switchboxes fail all the time , so it's quite likely this is the problem a lot of dealers keep the switchboxes in stock because of this.
