1964 50 Hp Mercury, No spark on 2 cylinders

[w2much]

My manuals go from 1965 up. I actually found an old manual for this engine and have ordered it but it will be a week or so till I get it. In the meantime I would like to see if I can do anything. I have no clue as to this old ignition system. I have a parts diagram that's it. I am going to put in new plugs, look for bad wire and check for continuity where I deem helpful. Can any person offer suggestions on where to start to look. This old system is completely foreign to me. Engine runs well as can be expected on two cylinders. Thank you in advance.

 

[GA_Boater]

Pretty sure your Merc 500 has a magneto, need a serial number to confirm. Wiring diagram - https://maxrules.com/oldmercs/Wiring/1966ona/25.jpg

Which 2 cylinders are dead, 1-2 or 3-4 or another combination? How are you verifying spark?

Asking because carb issues can kill the the top two cylinders or the lower two cylinders.

 

[w2much]

I am going to boat now. It is not the top two nor the bottom two.MAy be 2 and 3 or 2 and 4. Will know in a half hour or so.Just pulling the plug caps off. Serial # 1639473 - 1755548 .exact not known right now.
Thank you. Stick with me if you can.

 

[GA_Boater]

Pulling plug wires off doesn't verify spark. All it shows is which cylinders aren't working. A spark tester is needed to look at how strong spark is.

 

[merc850]

Look for wires rubbing against block, spark plugs that are shorted by deposits and you should remove the cap and look at it for corrosion etc. If you are going to replace wire(s) they are held in by small screws beside the contacts - don't just pull them out.
Do a compression check as well.

 

[GA_Boater]

And those small screws for the plug wires like to seize in the cap and break off.

If you remove the magneto be very careful - Parts are hard to come by and cost an arm and a leg.

 

[racerone]

The 65 manual would work for a 64 model.-----No difference.-----Split the distributor, just 4 bolts.------Clean and set points to 0.010"------Test for spark before re-installing.

 

[w2much]

After finishing the cylinder block gasket yesterday I started the motor but was in a rush to leave. Of course I did notice two cylinders not firing. Thanks to all for reminding me of the simple checks. Because I dreaded an ignition problem with this motor I naturally figured it was bad karma time again. Yes there was spark on all four cylinders. They were running so rich the plugs could not fire. Not a really strong spark though. Jumps 1/4" at best. Just adjusting the idle air mixture about 2 full turns in and this baby was sounding good.
OK now moving on. I need to do a link and sync. I can not get this thing to a low idle. I am seeing the throttle plates closed but the distributor body is hitting the carburetor. Looking from the front of the motor as I turn the distributor to the left the idle gets lower. It remains smooth though . If it were to go a bit further to the left ( clockwise I guess ) it would lower the idle speed. The problem is that it hits the carburetor and can not go any further. I am thinking a car distributor . If not aligned on the proper spine you can not adjust the timing correctly. Any thoughts here, besides " This guy is really ........ ...."
Thank you for your replies , all of them.

 

[Chinewalker]

When you get your manual, check the timing as per the book to make sure the timing belt is properly aligned.

 

[w2much]

I am obsessed . It came to me in my sleep.Actually Racerone suggestion of looking at my newer manual was wise indeed. Then Chinewalker confirmed my dream . Must be the timing belt. I will post my results when I am done. Thank you all again

 

[w2much]

Just put a few more hours into this beast. The timing belt was indeed off 1 notch. I tried everything to get a low smooth idle but could not get one. Running out of tricks I decided to step back and watch it run then stall. Would only restart with the choke on and a fair bit of throttle. Started to run on 3 then 2 then 4 cylinders as I got the idle a bit lower . Mmmmmmmmmmm. Finally, should have tried earlier, I. Looked and looked and noticed the aviation gasket sealer on the block, crankcase joint. Sprayed some electrical contact cleaner ( all I had with me) and instant stall. Tried a few more times same result. I believe I have found the culprit.

 

[w2much]

Is there a way to test the crankcase seal before getting started or before starting an outboard.I don't see how it could be done .Perhaps spraying soapy water and then cranking? Force smoke down the carb throat past the reed valves?

 

[Chinewalker]

Evidence of oily seepage from the seam? That's usually a dead giveaway...

 

[racerone]

Some soapy water on the joint should show bubbles when turning the flywheel with a rope.-----I am not sure your test with contact cleaner proved that there was a leak !!!

 

[w2much]

OK .I would rather be wrong. I am going back there in a little bit with a can of starting fluid. I will spray it in several areas. Why would the motor stall out so abruptly being sprayed on the joint. Can that gooey aviation gasket sealer be used on this joint? Or will it slowly dissolve with fuel air mixture flowing. I ask because I do not know.

 

[DeepCMark58A]

Starting fluid is not good for a 2 stroke motor.

 

[racerone]

Did you look at the label on the contact cleaner ?-----What is in that can ?-------I believe your testing is flawed and you might be jumping to conclusions about a leak that likely does not exist !

 

[w2much]

I realize starting fluid is a no no. I never use it to start a motor . I usually use a fuel oil seafoam mix. But you caught me. Was just looking for vacuum leak. I too thought, now I don't know what to think of my crankcase leaking. I tried again (yes with starting fluid). The constant is when I spray it on the crankcase joint the motor stalls out quickly.

 

[racerone]

Any pictures of the area where you " think " there is a leak ??----Does soapy water show bubbles , yes or no ??

 

[w2much]

Boat is not here so no pics. I can't give a yes or no on the soapy water. Last visit I sprayed soapy water while running but not as suggested because the top part of the cowl was on which did not allow me to crank slowly by hand. While running, my bad idea, was inconclusive because to much air was moving around for bubbles to form or not . Appreciate u hanging in here with me. I will post more as I go.