100 hp 2+2 2 stroke Merc starting issues

[bgailitis]

I have a 1989 Mercury 100 hp 4 Cylinder 2+2 2 Stroke outboard. The motor had a high speed issue the first time I took it out this year. I looked at the electrical. Checked rectifier, stator, battery charge and all seemed to be OK. Changed the spark plugs and the engine took off at high speed smooth right up to 5500 rpm. I thought I licked the issue but after about 30 minute drive I slowed down and the engine stalled. Then it wouldn't start up - all I could get is a backfire out of the exhaust.

Now in examining all of the electrical part I did pull off the flywheel but as I said it ran good for 30 minutes.

What do I look at next? I cannot figure out how to diagnose a trigger. I am wondering if that is intermittent. I did see water coming out of the engine as I started it up and the engine turns over freely.

I would appreciate some of this boards expertise to assist me.

Thanks

 

[bgailitis]

Re: 100 hp 2+2 2 stroke Merc starting issues

Took a look at the flywheel. The key was sheared off - So that explained the backfiring. I realize now that I didn't torque the flywheel back on. Would this be responsible for shearing the key?

 

[Texasmark]

Re: 100 hp 2+2 2 stroke Merc starting issues

Took a look at the flywheel. The key was sheared off - So that explained the backfiring. I realize now that I didn't torque the flywheel back on. Would this be responsible for shearing the key?

Yes

It doesn't take much on some engines to really screw up the timing. I had a small OB once that I hit a stump and it quit running. In short, I had only partially sheared the woodruff key but that was enough to mess things up.

Mark

 

[bgailitis]

Re: 100 hp 2+2 2 stroke Merc starting issues

Looks like I got it licked. The motor has run many hours without this failure.