yamaha 115 died and won't restart

[GreyCrow]

took off for a sea trial after reringing the yami and after getting about 2 miles out the motor quit. couldn't restart so we had to use the kicker to get home.
can't find any blown fuses, the motor cranks over but no pop. it is getting spark in all 4 cylenders.
can someone point me in the right direction for trouble shooting this thing? I'm scratching my head bald!
GC

[99yam40]

Check compression and spark on all cylinders.
Then make sure it is firing at the proper time(check timing while cranking)
You may have sheared the key in flywheel.
If all of that is good then look at the fuel/air mix

[GreyCrow]

just a question about the key in the flywheel...
how the hec could that happen?!
I really haven't checked the compression yet but it feels like that's not a problem. I do have spark at all cylenders. the motor rolls over with the key and I can wrap a cord around the flywheel and pull but to the same end. no start.
could water have gotten in to the carbs and shut it down while we were motoring? I noticed water splashing up over the transom and my friend thinks that it may be mounted too low. we're both scratching heads now...
I'll be checking for compression tomorrow as we dig a bit deeper into this issue. we're stumped on this one for sure.

[GreyCrow]

OK I just did the Compression test not knowing which cylender is called what I will just say that the upper right looking at the back of the motor has 115 lbs, the lower right has none! that's news I didn't need to see. the upper left has about 110 and the bottoem left has 50.
so I'm about to look at the manual to see where I could be loosing this pressure but I still have that question about the fly wheel key sheering (we didn't go into a bed of kelp or anything it just quit). anyway that aside can anyone shed light on what would cause the compression failure? reed valves sticking or broken?
there is no odd noise coming from the motor as we turn it over, it's a clean turn each time.
Bummbed we couldn't use the boat for the daughters wedding!

[99yam40]

Blown head gasket, broke rings,or hole melted in piston.

Pull the plugs and look to inside or pull the heads and inspect.
Did you break it in with double oil? or did you just fire it up and go when it blew.
Why did you re-ring it and what all did you do to it?

Being it is the bottom 2 I would be looking at the bottom carb not getting enough fuel or plugged jets causing motor to run too lean on those cylinders.
But you first have to find out what is causing the low compression and then find out what caused it.
I would not worry about the flywheel right now unless you find it sheared when and if you tear it off again. They can shear if flywheel is not tightened properly

[GreyCrow]

ok
never mind!
I found that the crank came loose and I got a power head full of bearings and loose parts.
I guess the motor is toast!
so much for this project.
thanks anyway
GC