Classic fifty nightmare

[sebastianguerrier]

I have a Mercury Classic 50, 45HP outboard motor that is giving me quite the head ache. The boat had sat for 12 years before I got it so I did all the basics to make sure there was no major damage to it before I started to order parts. The compression test showed 125 +/- 4psi, cylinder leak down is 8% or less, intake has vacuum at the fuel pump port, carbs were gummed up so I cleaned them and have 35kV spark, everything looked ok.

So now the motor cranks, kicks and trys to start, but wont start unless taken to half throttle or higher. As you idle down, the motor will sputter and quit. I placed an inline spark tester and found all cylinders are firing as it quit. I checked the base timing and my flywheel lines up perfect with TDC. I then marked the location of TDC of all cylinders on my flywheel and checked the spark timing of each cylinder with my timing light and all are firing near the timing mark.

Where should I go from here?

 

[racerone]

Is the choke / enricher working properly ?---Also sounds like carburetors may need more attention.

 

[sebastianguerrier]

The choke is working fine and is releasing normally. With the idle mix screws at 1 1/4 - 1 1/12 turn gives the max rpm I can get out of it. If you richin the mix or choke it dies instantly.

 

[sebastianguerrier]

Took the trigger plate off looking for any indication of a chaffed wire or something, and noted this little crack in the magnet on the flywheel magnet. does any one know if this is normal from casting or is it a crack that may be picked up on low rpm.

 

[flyingscott]

Is the throttle assembly moving correctly? Link and sync is done? Sounds like your carbs need a good soaking.

 

[sebastianguerrier]

So the problem was the plugs :mad-new:.:I don't know what the difference between the plugs that were in it but after cleaning the carbs again an re-syncing them (which didn't do anything new), I had decided that even though I had put plugs in it, I may have gotten a bad one. So before I re-ordered another set of the plugs that where in it. I figured I'd double check the service manual. Sure enough I found that the plugs that were in it had a "W" in the part number and the ones in the manual had a "2". So i ordered the ones from the manual and that was the end of that. Just another instance where cross referencing and book work would have saved a lot of time and effort. I hope that this might help some one else out there.

 

[nipperdog]

Glad you got it figured out. Just so happens the 50 I'm presently working on had the wrong plugs in it when it arrived. I wonder how that happens, do folks think if it screws in the hole that's close enough? If I ever did something like that I'd probably end up with a hole in a piston.