merc 500 cooling and ignition problems

[grossm1]

Hello all, newbie here...

Down to brass tacks! I recently purchased a mercury 500 blue stripe, and am in the process of rebuilding it. I cleaned the carbs, and when I fired it up, it idles very radically. I am not new to motors, and was fairly confident the problem was the ignition - especially since the motor would kick back every now and then. So I went to look at the timing, and noticed the arrow on the distributor pulley and the mark on the flywheel did not line up. So I aligned them - like the manual said - and now it doesn't run at all. It definitely ran better when the marks were 'off'. Why is this? Its just lining up two marks - can there be any trick to this? Why did it run better when the timing marks were not aligned?

The other thing is the motor does not pump water very well. I took the lower unit off and attached a hose to the copper pipe for the water and nothing came out the pee hole - in fact, it appears there is a leak somewhere because all the water I put in the motor falls back out, without even getting into the powerhead. WTF? are there gaskets that commonly fail that I should look for? Where does water get into the power head? I should also note that when I did have the motor running, it only peed water under high revs - and very weakly.

Any thoughts??????

I'll post pictures shortly...

 

[grossm1]

Re: merc 500 cooling and ignition problems

Well folks, here is what we have:

The base gasket where the powerhead connects with the leg was blown. I went to clean it out and found parts of the old impeller in there clogging everything up. I think this pressurized the cooling system too much, blowing the gasket. So I fixed the cooling problem.
So anyways, I sealed everything up proper (used gasket maker) and ran it. Then it ran fine on the top 2 cylinders, but not the bottom 2 - so I took the bottom carb apart, cleaned it - again- and reassembled everything. Now the bottom two cylinders work fine, but not the top two. WTF...
With regards to the timing, everything was fine. Turns out my flywheel actually had two white marks on it. A quick test with the timing light showed that when I reset the timing, I lined it up with the wrong mark on the flywheel.


As of now I am not sure why the top and bottom pairs of cylinders switched working when I merely cleaned the bottom carb. I know all the cylinders have spark, and I know the spark is timed correctly, so it MUST be a fuel problem. Today I will run the motor again, and I will spray some carb cleaner in the top carb and see if i can get them to pop off. That will prove that it is in fact a fuel problem.