Classic Mercury 50 Help

[csvencer]

Been fighting my 82 Mercury 50 4 cylinder for about a month and am ready to throw in the towel. Here is what has been done so far.

-Carbs cleaned and rebuilt
-New stator
-New coils/plugs/wires
-New rectifier
-Fresh gas and fuel line
-Trigger tested good (I have the merc manual)
-Timing off 180 degrees (#2 is firing when #1 should be but is in spec...)
-Compression 80, 84, 85, 80

Issue I am having is the motor starts great and idles fine just boggs under load. It hesitates and boggs once I put a load on it and I can't figure out why. I know the compression isn't perfect but they are all even and I am chalking it up to a crappy tester and/or not being completely warmed up when I did it. Any ideas what I am missing? I know it's either a fuel or ignition problem and based on the 180 off thing I am leaning on ignition but have no idea what else I could change out or what would be causing it to fire off a half turn like that.

Is it time to throw in the towel or what? Any help would be appreciated.

Thanks.

-Svence

 

[Wingedwheel]

Re: Classic Mercury 50 Help

Svence, the compression is equal, but IMHO its a bit low for my liking.

 

[Maxz695]

Re: Classic Mercury 50 Help

spray a little oil into the cylinder and recheck the Compression for a true reading

 

[csvencer]

Re: Classic Mercury 50 Help

Should I spray it down with oil before or after I let it run for a bit? I let it idle for a bit before I did it the first time but I don't think it was completely warmed up. Would compression be the issue all along? I figured it was a little low but they were all even so I wasn't too concerned.

-Svence

 

[Faztbullet]

Re: Classic Mercury 50 Help

Which carbs do you have, Walbro or Tilliston? Did you install the correct carb kits? Is sync and link correct? What happens if you bump choke when its "boggs"? What are you idle mixture settings?(1-3/4 turn out) That switchbox is upside down on that engine, it fires the bottom to the top, #1 coil is at bottom terminal(grn) and #2 is on second from bottom(grn/wht). Check the wiring on switchbox to ensure wire are in their correct positions....

 

[csvencer]

Re: Classic Mercury 50 Help

Tilliston carbs and I got the part number right off the diagrams so I am pretty damn sure they are right. Linked and synced, timing is way off (180). Idle screws are backed out almost all the way and that seems like the best position for them, idles in forward without stalling. If I bump the choke it helps for a sec then boggs, tapping it repeatedly doesn't help keep her going, just runs real rough and dies/boggs as I go up in throttle. Not sure what the wires are off the top of my head but they are installed just like the Merc manual has.

-Svence

 

[Maxz695]

Re: Classic Mercury 50 Help

adding oil to the cylinder when checking for compressoin creates a better seal if theres a leak it will go by the ring and you,ll get a better reading. You can do this cold start to check compression as things tend to expand when hot. Turn the engine a few revolutions to get the reading.

 

[shawpdx1]

Re: Classic Mercury 50 Help

That Compression is your problem. IMO

 

[csvencer]

Re: Classic Mercury 50 Help

I am hoping it's not the compression. I will have to get another gauge and do it again after I let it all warm up. Didn't think that it would be that much of an issue but I could be wrong.

-Svence

 

[csvencer]

Re: Classic Mercury 50 Help

Haven't had a chance to recheck the compression but did do a reality check on the timing issue. Was thinking my timing light was off but just pulled the #1 plug and found TDC to be off by 180 just like I was getting. Flywheel is keyed only one way so I have no idea what to do now.

-Svence

 

[Maxz695]

Re: Classic Mercury 50 Help

well switching wires on a 2 cyl would work but set the #1 piston at TDC use a gauge to verify the piston is at the top. then unbolt the flywheel and reset it where the timing mark says ZERO on it to the timing marker point. tighten it back down and you are all set. But if this is a four stroke your piston will come to the top 2 times in a cycle. that is why they call it a four cycle. Put your finger over the spark plug hole and as soon as you feel compression you are on the power stroke bring the piston to the top and then check the flywheel is set at 0 to the timing marker

 

[csvencer]

Re: Classic Mercury 50 Help

How do I unbolt the flywheel and adjust, it's keyed to the flywheel...sorry if it's a stupid question just not sure I follow.
Here is what I am dealing with...
https://picasaweb.google.com/lh/photo/QKKmMA0XWjkfXJFVrcMSeQ?feat=directlink

-Svence

 

[csvencer]

Re: Classic Mercury 50 Help

Also did a quick TDC check on each cylinder...#2 is 0 degrees TDC, #3 is 90 degrees, and #1 is 180 (approximate, no dial indicator used), #4 is a pain so I didn't do it just for this. Will swinging the flywheel around mess these up or are they firing right, just 180 off?

-Svence

 

[csvencer]

Re: Classic Mercury 50 Help

Redid the compression. 120 on the top three, couldn't get to the bottom with the gauge but assume its similar based on the previous results. Also took a stab at the timing and it sounds pretty smooth but havent had a chance to splash it yet and run a wot run. Oh, and sound the flywheel around 180 and that fixed that.

-Svence

 

[csvencer]

Re: Classic Mercury 50 Help

Getting closer. After fixing the flywheel I got to the timing and think I have it right. Book is a little confusing as far as what idle and the other setting is (is idle in nuetral or just clutched in?). It has you run the boat in gear up until it is within timing spec but doesn't give you an RPM or any idea how far advanced the throttle should be. Anyone have a pointer or two?

-Svence