A Little Background:

2005 Briggs 35 on an airboat. Heads, Mikuni, Cam. No Rev Limiter. No Governor. No Kill Switch(that I'm aware of). Recently replaced the crankshaft. Got everything back together Sunday, and cranked it up. Ran for 10 seconds and shut off. Turned the key and noticed that only the fan guard was turning. Yep, I sheared the key on the flywheel. Replaced the key and cranked the motor up and it ran fine. Revved it up and down for 3-5 minutes and then shut it off.

Come home Tuesday and figured I'd run it again on the trailer. Cranked it up, and it ran for about 15-20 seconds and then shut off. Would not crank back up. Figured I might have flooded it so I gave it some time. Came home last night and it still wouldn't crank, so this morning I did the following.

1. Checked valves to make sure they were set right(.005). Made sure push rods were on the rockers.

2. Took the Mikuni Carb off my mud motor and put it on my airboat. Still would not start. Put it back on my mud motor, mud motor started right up. Mikuni on airboat is full of fuel and the Accelerator pump is spraying fuel down the carb throat when I press the throttle.

3. Took the spark plug wire off, and pulled the spark plug. Put it back into the boot and turned the motor over and got spark. Opposite side is connected to the Tach, and it was reading 1350rpms while motor turned over.

4. Sprayed Quick Start into the carb, turned the motor over and it doesn't even act like it wants to start.

5. Pulled the choke lever and let it spin over for a few seconds. Got a few pops out of the muffler, but that's all.

6. Unplugged the oil sensor wire and still no start.

7. Drained all fuel from carb, fuel lines, and made sure fresh 93 gas got into the fuel system.

At this point, I would think the issue is spark, but the plugs have fire, so I don't know if I should mess with the Coils/Diodes or not.

I gapped the coils about .003-.005 from the flywheel when I installed them.

Now that I think about it, at .003-.005, there was some rubbing when turning over by hand, so I chose one of the larger sizes until there was no rubbing.

So I should check and re-gap the coils.

Do a Leak down test.

Anything else coming to mind?

To eliminate all the wiring harness, disconnect the grounds to the coil while you have the cowling off and try starting it. Warning- you will have to choke it or pull the plug wires to turn it off- also keep clear of the fan.

Another thing- seen batteries turn a motor over well, but just not enough to kick it over- really hard starting. You can swap the battery on your motor that starts and see if this one cranks up.

I'm not sure of the actual gap in your coils but I have always used a bussniess card to gap my coils. If the other 2 guys above me speak take there word for it thou

sounds like a timing issue to me. as far as setting air gap two cerial box tops stacked together will get u on the money as far as air gap goes.

Are you SURE your valves are right?

What about the nut on the crankshaft that holds the flywheel on, are you torqueing it to specs?

time to pull it back down and ck ur work. ck ur timing marks. could put it up on tdc and ck ur cam position. does it turn over easy by hand with plugs removed.

After reading a little bit online, it appears I had the concave washer turned the wrong way. I'm sure that was my issue. Now I'll replace the key, put the washer in right, and torque to 65 ft lbs. it's always the little things with these motors.

Who would have thunk a washer turned the wrong way would cause this!!

Sell it and get this http://tallahassee.craigslist.org/boa/3266591541.html

Whoa, wish I had money like you, I'd offer him something for it and camo that basterd. LOL

I thought the price was missing a one in front of it...

At least my shit runs!