Messed up my 2001 Mercury 50

[graysilm]

Yesterday I was running my motor on the engine flusher. I went inside for a minute and came back out and my overhead alarm was going off. I immediately noticed that the motor flusher had vibrated off the water intake holes. I quickly put back over the holes and it began pumping again. Within about a minute the overheat alarm turned off. Now my motor runs like crap. It doesn't idle well, and when I have it reved up it runs decent, but misses every now and then. I tested my compression and I have 105 on the top cylinder, and 120 on the bottom two. I am furious now. Could it be something simple like I blew the head gasket, or is this going to have to be torn down and rebuilt? Can I check to see if it the head gasket by spraying some soapy water around it? And advice would be greatly appreciated.

 

[skynyrdcat]

Re: Messed up my 2001 Mercury 50

Wow, sorry to hear that!

I think at this point you have nothing to lose by pulling the head (it's going to be coming off anyway).

This will give you a better idea of what has happened, you can check the rings and cylinders, check the head for warpage, etc.

Look for scarring in the cyl bore (with piston down)

If you have calipers to check the bore, check them at different places and should not see more than .003" difference from any spot to another.
If all looks good, you may need some telescoping gages to check the bore at the middle and bottom of the cyl as well.

I think the stock bore is 2.955" (but don't quote me on it).

Their is a "slim" possibility that you can tilt your motor up, poor some oil in the spark plug holes (let it sit over night) and tap on the pistons (with something that won't crack them) the next day. If the rings stuck it may un stick them (but don't count on it).
If you try this, then check the compression again and see what you get.

 

[skynyrdcat]

Re: Messed up my 2001 Mercury 50

By the way, look closely at the gasket area between the cyl for signs of combustion. Generally heads will warp in the thinner areas (if it did warp), and the loss of compression could be from one cyl to the other, not neccesarily to the outside.

 

[graysilm]

Re: Messed up my 2001 Mercury 50

My head is integral with the engine block. tonight a guy I know who is a mercury outboard mechanic came by and tried to troubleshoot what is going on. He said that the cylinder with low compression isn't pulling any air into the carburetor. He thinks the reed valves are damaged on that cylinder. Does this sound right?

 

[thefairlaneman]

Re: Messed up my 2001 Mercury 50

The part about going inside is what I cant understand. Why would you do that?

 

[graysilm]

Re: Messed up my 2001 Mercury 50

I went inside to take care of some other things while I let the motor run. It was stupid. Lesson learned, now I'm trying to figure out what to do now, not what I should have done then.

 

[graysilm]

Re: Messed up my 2001 Mercury 50

Update!!! Now that I correctly tested my compression my numbers are better. Before I had the throttle in neutral. When I opened it to WOT and sprayed some oil in the cylinders my numbers are 120 top, 123 center, 120 bottom. My top cylinder is not getting any air when running. Any ideas?

 

[KeyWestBoater]

Re: Messed up my 2001 Mercury 50

I think I will change my flushing habits due to your post. I've been in the habit of flushing my motor while washing the boat. So while the motor is on the muffs I'm washing the boat but not necessarily keeping an eye on the motor. Although thankfully this hasn't happened, there's opportunity for the muffs to vibrate off while I'm washing away from the engine. From now on I will keep my eyes on the muffs until I'm done flushing. Saving a few minutes isn't worth ruining my motor! BTW I hope everything turns out ok with your Merc and you get back in the water soon.