1957 Mercury Mark 55 Won't Start

[jcohen]

Hello Old Merc Fans,

I rescued a 1957 Mercury Mark 55 I came across in Craigslist. I drove 3 hours to Palm Springs, CA, to buy it and upon arriving there, I discovered it didn?t have a lower unit. To make a long story short, I bought the old ?legless soldier? anyway.

I rebuilt the fuel pump, installed new fuel lines, rebuilt the carburetors, went through the mag and replaced the points (set them at .010) and condenser and cleaned all the other contact points, replaced the spark plugs with AC Delco R43s, purchased a lower unit from eBay and replaced the bearings and water pump. I verified the mag delivered a good spark down all 4 wires and then reattached it, making sure the timing marks lined up per the Mercury Master Service Manual.

I've tried to start the motor a couple of times now. It has great compression in all 4 cylinders so I can pull on it only so long before my arm tires. I've got it to pop a couple of times and backfire. I thought maybe it's pre-igniting (although I don't see any evidence of that in the mag) so I bought a second mag, went through it and made sure it was okay, and then installed and tried it but had the same result. I also shot gas directly into the carbs but if it does anything, it usually backfires.

I'm thinking it may be the reeds. Can anyone help solve this mystery?

Truly befuddled,
Jeff

 

[Texasmark]

Did you set the mag timing correctly? What is your compression?

 

[tlewick1]

Did you check the timing with a timing light? When I resently rebuilt an engine, I installed everything back the way the manual said and still found the timing was way off. Make sure it's right with a timing light.

 

[jcohen]

Hi Texasmark & Tlewick1,

Thanks to both of you for your prompt replies!

I lined up the little arrow on the pulley with the line on the flywheel, per the manual. The compression in the engine is 125psi per cylinder.

Because the problem does indeed seem to suggest a timing problem, I'm trying to understand how the timing could be off if you line the marks up properly. The pulley can only go on the shaft one way and the believe the same is true for the flywheel. However, is that true for the flywheel?

Thanks again for your help!

Sincerely,
Jeff

 

[racerone]

Did you remove the top plate of the distributor pulley to line up the timing marks ?

 

[jcohen]

Hi Racerone,

Yes, I did.

Jeff

 

[tlewick1]

I don't know how yours works, but the timing was adjustable for mine ('78) depending on the throttle cable preload.

 

[jcohen]

Thanks again tlewick!

I can't really use a timing light since my motor is pull- not electric-start. I'll probably use a combination of a dial indicator and a multi-meter to figure out true TDC and when the points are actually opening and closing.

Would your motor even start before you got the timing right with your timing light?

Sincerely,
Jeff

 

[tlewick1]

Not really.

 

[jcohen]

Hello Gentlemen,

I got my Mercury Master Service Manual out last night and re-read the timing portion (somewhat confusing, by the way), then rechecked my motor, and discovered I had incorrectly lined up the timing mark on the pulley with the "0" line on the flywheel. Who would have "thunk" that "0" actually means .235 before TDC!

Anyway, my plan is to readjust the magneto-to-flywheel setting and then retry starting the motor this weekend. I will circle back with the (hopefully good!) result.

Thanks again for your suggestions!

Sincerely,
Jeff

 

[jcohen]

Hello again Gentlemen,

Well, as it turned out, I realigned the arrow on the mag pulley with the proper line on the flywheel, but the motor still would not start. Arrrr! At least, though, it didn't backfire this time and scare my neighbors!

I have gas at both carbs but squirted some in the carbs anyway but it didn't make much difference. It never seemed to catch. I double-checked the spark and confirmed I had it all 4 wires.

Anyway, it still seems like a timing issue and since the motor is pull- and not electric-start, I ordered a dial indicator and will double-check the timing using it and a multimeter.

Thanks in advance for any additional ideas or suggestions!

Sincerely,
Jeff

 

[racerone]

Does spark jump a gap of 5/16" or more, yes or no ??---And you can check timing with a timing light.---Just use a garden tractor battery to power the light !

 

[jcohen]

Hi Racerone,

Yes, the mag jumped a very healthy spark before I reassembled it and I've confirmed spark down all 4 wires.

I can't really use a timing light since the motor isn't electric start and it won't start.

Sincerely,
Jeff

 

[racerone]

You can use a timing light while the motor is being pulled over .-------Have an assistant pull it over !!---Electric start has nothing to do with operation of the timing light.

 

[jcohen]

Oh, okay. Thanks Racerone! Good to know in the future!

For now, though, since I don't have an assistant other than my wife who will most certainly decline if I ask her, I'll probably use the dial indicator and multimeter.

Should I find that the timing is indeed off, do I change it by adjusting the timing belt or by loosening the bolts on the magneto plate and moving the magneto? That plate is also tied to the carburetor pickups so moving it will throw that adjustment off.

Thanks for any additional forthcoming suggestions!

Sincerely,
Jeff

 

[racerone]

I have a number of these early 4 cylinder Mercury motors.---I can not offer you any further help.