Mariner 15HP No Start

[greene1564]

I bought a 1984 Randall Craft 14' boat, it has a Mariner 15 HP outboard on it. The engine had been running well except for the spark plug wires have been sliding off the plugs. Today I changed both plugs and slid on the wires and they fit tight on the new plugs. I took the boat out and the engine ran better than it has before, I was impressed until all of a sudden at full throttle the engine quickly bogged down and died as if some cut off the fuel. I pulled the cover off and the plug wire was off the plug. I replaced wire and was not able to get the engine to start back. It will fire for a second then die. I replaced the wire boot assembly on both wires because they fell apart when I pulled on them. I thought this should fix the problem, however no the same thing. I am getting fuel to the Carb and fire to the plugs. I do not know if it is just flooded and unable to restart. I pulled both plugs and I am going to let it sit until I get home from work tomorrow to see if this works. any other suggestions would be appreciated. the engine is a Mariner 15M 684 C 026169. Thanks for any help

 

[Texasmark]

Mercury and I suppose Mariner also being they are both Brunswick companies and share a lot of parts, use a 40,000 volt ignition system. If you don't know it, that much voltage if left unharness can play heck with a lot of components. In normal operation the voltage never gets that high because the plug fires way down around 10,000 volts, but if it's cranky it may take more and the ignition system is right there with whatever it takes.

Since you said you had problems with your caps coming off your plugs, every time a cap came off you had an unloaded high voltage circuit and may have had a high voltage breakdown in one of your components. Since everything was working fine and all of a sudden things stopped working, that's the first place I'd look.

I'd start with a timing light hooked to a plug wire to see if it fired when you cranked the engine. Check both plug wires with them connected to the plugs like they are supposed to be when running.

Then if no fire you need to back up the line to see what crapped out. One thing that may help would be to wait till after dark and look for sparking in the high voltage components. Then take resistance measurements of the ignition system. If you don't have a service manual, go to the top of this page and look in the "Boat Parts and Accessories" section, putting the words "Seloc Service Manual" in the querry box. You can rent online time in a manual or buy one out right. I did the online usage and it worked for me.

Resistance measurements aren't fool proof with high voltage problems as unless a part blew open or shorted out, carbon track kind of thing also, you have a hard time finding the smoking gun with an Ohmmeter.

Good luck.

 

[flyingscott]

Hello I am pretty sure you have a yamaha built mariner somewhere on your motor it should say built in japan whole different animal than a mercury ignition get the manual