Assuming you have compression and mechanically it's OK, I'd pull the plugs for inspection then squirt a little gas in each cylinder then replace the plugs and try to start. IF it fires up even a little then I'd look at the fuel side again .....
What year motor you working on? A 650 Merc would be from the 70's how's the wiring harness look? The Mercs from the 70's are notorious for having rotten wire sheathing.
What Waterman may be trying to tell you is that most of the wiring involved in the correct operation of your motor is "suspect", if it hasn't been replaced. The only major electronic part that hasn't been replaced is the trigger on my 1977. The trigger got a shrink wrap job that turned out to work just fine for now. Spent more time working on the motor than fishing so for now it is enough. My trigger is not like yours as I have a motor with no distributor.
I replaced just about everything electronic and fuel related on my 79 140 horse, so I've been there but knowing what newer motors cost it was cheap. Now it starts up and runs great, like new even.
I got the motor started the other day after it sat for 3 years I was useing the ear muffs and a buddy told me I could put it in a trash can with water. So I shut off the motor a tilted it up and put it in the trash can and now it won't start
I see why you're looking for the mercury switch now. These older motors will spill fuel out the carb throats when they're tilted all the way up and they could be dry. Did you use fresh fuel? How did you check or test that the motor is getting spark and fuel? Does the motor turn over at good speed with the starter but just not fire up now?
Being short and seemingly ticked off won't help get your Merc going and tends to make other members shy away from posting any ideas.
I checked the spark with the spark plug out and hooked up to the wire. Then someone said to test it with the spark plug in the head and use a oldto test it
Just one plug then, so was the plug wet with fuel when you removed it from the powerhead? A spark tester is the best way to do the test and on all the plug wires.
Also a compression test on the motor would be a good idea.
It ran on muffs and won't run in the barrel. Has any carb work been done? If the needles aren't set right, running on muffs and not in water is a symptom.
Mattcm- That kill switch may be near the top front corner of your face plate(large metal front that protects the carbs) Starboard side of the motor. I'll look at my 69 in the morning and post a location. You may also find it if you follow the blue wire. You will need to take off the top cowling pieces.
