1957 Mercury Mark 55

[old boat NC]

I have what might be a dumb question.<br />I just bought a 1957 Mercury Mark 55 engine. It is an electric start. The boat did not come with a battery. Did this motor use a regular 12 volt boat/car battery? Thanks.

 

[Laddies]

Re: 1957 Mercury Mark 55

Yes it's 12 volt

 

[mixerjv]

Re: 1957 Mercury Mark 55

You might want to double check the year or better yet polarity, the early Mark 55 electrics were positive ground. A true 1957 is negative ground.<br /><br />Also you may or may not have a charging circuit, it was an additional option. If you do have the charging circuit (stator and rectifier) and it's the original rectifier, the rectifier is probably shot by now (they didn't last long). You can replace it with a common radio shack bridge rectifier, i'll give you the part # if you need it.

 

[old boat NC]

Re: 1957 Mercury Mark 55

Thanks for the info. I think I should buy a manual! <br />Could you tell me how to check what year the engine is. Is it based on the serial number?<br />Also, how can I tell which polarity it is.<br />Finally, how will I know if it has a charging circuit?<br />Thanks again... <br />FYI, this engine has been sitting in a Kansas hay barn for the last 35 years! It looks like new. I was planning on putting in a new impeller, new lower unit oil, cleaning the carb, etc.<br />Any other suggestions?<br />If there is a way to post a picture of the motor, I will. (I am new to this forum.)<br />Thanks again!

 

[Laddies]

Re: 1957 Mercury Mark 55

All Mark 55s were 12 volt negetive ground engines. If you want a Mercury manual the part number is 90-25500

 

[Chinewalker]

Re: 1957 Mercury Mark 55

Hi MVP,<br /> Year - yes we'll need the serial number.<br /> Negative ground.<br /> Charging circuit - there will be two yellow wires leading from under the flywheel to the rectifier (series of metal plates).<br /> Replace the fuel pump diaphram, too. Cheap and easy to do!<br /> Lots of good stuff at www.oldmercs.com...<br /><br />- Scott

 

[old boat NC]

Re: 1957 Mercury Mark 55

My serial number is 980800. What year would that be?<br />The engine does have a charging circuit. How will I know if it is shot or not?<br />What part can I get to replace it.<br />Thanks again for all the great advice.<br />John

 

[Chinewalker]

Re: 1957 Mercury Mark 55

Serial numbers 906752 thru 983919 were 1956 model, so yours would fall into that range...<br />A Radio Shack bridge rectifier can handle the duties. I think if you do a search on the Merc forum you'll even find the part number.<br />Personally, I wouldn't worry about the rectifier and charging system until after you've got everything else sorted out on that motor. A good battery ought to give you at least a month of starting before needing a charge, so the alternator can wait...<br />- Scott

 

[mixerjv]

Re: 1957 Mercury Mark 55

Laddies - the Mercury service manual does say that early 55E's were positive ground.<br /><br />The radio shack part number on the rectifier if needed is 276-1185

 

[Chinewalker]

Re: 1957 Mercury Mark 55

That would be the "sling shot" style starter motors only found on 1955 Mark 55s. All standard Bendix style starter motors run on a negative ground, found on 1956 andup Mark 55s..<br />- Scott

 

[Laddies]

Re: 1957 Mercury Mark 55

OK, mixer I didn't realize that they used the slingshot bendixes in the earliest 55s I thought they were discontued after the Mark 50s, can't belive I never ran into one--Bob

 

[old boat NC]

Re: 1957 Mercury Mark 55

Thanks guys for all the info.<br />So it sounds like it is a negative ground.<br />Worst case scenario... the battery is connected wrong... what would happen? Would the starter turn the wrong way? Or worse?<br />Thanks...I'll connect it with a neg. ground and I plan on trying to start it this weekend. I'll let you know the results!<br />John

 

[Chinewalker]

Re: 1957 Mercury Mark 55

Hi MVP,<br /> Since your motor is a 1956, it will have a negative ground. Positive grounds were only found on early 1955 models. They had kind of a side-arm, or sling-shopt type of bendix which engaged the flywheel. Not my favorite method, and apparently neither was it with Merc, as they switched over to the more standard spin-up type bendix. <br /> Laddies, although I can't confirm this for sure, I am fairly certain that the side-arm bendix starters were only used on sandcast block motors. There may be a little bit of overlap, but they were both phased out in early 1955. Probably using up Mark 50 stuff (as Merc was apt to do). They had to redesign the top cowling to accomodate the taller standard bendix, squaring off the front of the top bubble on the starboard side.<br />- Scott

 

[old boat NC]

Re: 1957 Mercury Mark 55

Thanks again!<br />Yes, mine has the more standard spin-up type bendix just like you said.<br />I'll let you know how the project goes!<br />John

 

[mixerjv]

Re: 1957 Mercury Mark 55

mpvideo- a couple of more points,<br /><br />If you get serious with the engine as laddies says the manual is a must.<br /><br />Also, to change the water pump you will need the cover tool to do it without destroying a cover that has been on for 35 years. It's no longer available from mercury, there was a guy on ebay selling ones he made out of his lathe but I just did a quick search and couldn't find one. If your good with metal you could make one, you'll see what's needed once you get the lower unit off. I'm asuming it's a fresh water engine, that's a good thing, salt ate these engines up pretty good.<br /><br />Suprizingly Mercury still makes a few essential parts used on these old engines, such as the stainless steel water pump cartridge insert, points, distributor cap, rotor, cover, water pump itself, selected bearings, prop nut, prop nut, tab washer (funky washer you bend tabs to hold the prop nut), and more.<br /><br />Check out www.oldmercs.com as a great resource to order a parts list with pics and parts that are no longer made by mercury.<br /><br />Check out http://www.mercruiserparts.com/selectModels3.asp?type_id=MARK <br /><br />under Mark 55 for an online parts list (no pictures)<br /><br />Good Luck

 

[mixerjv]

Re: 1957 Mercury Mark 55

Oh, and if your going to run the engine out of water regular earmuffs won't cut it, you'll need Tempo's TEM380070 (940TFO) flushing device:<br /><br /> http://www.oldmercs.com/tools.htm <br /><br />down near the bottom.

 

[old boat NC]

Re: 1957 Mercury Mark 55

Thanks everyone for the great advice.<br />We attempted to start the engine this weekend. <br />-Timing belt had broken and I have ordered a new one from Old Mercs.com<br />-Also ordered a service manual.<br />-The engine cranked up, the compression was great, but that is as far as we got.<br />-I have also ordered carb rebuild kits, and fuel pump kit.<br />BUT, the big deal is that it appears my lower unit is frozen. (I had to remove it to get the engine to crank.)<br />There are unusual dings on the REAR of the skeg and prop... almost like someone BACKED into something with the motor (either in the water, or on the trailer). May explain the frozen lower unit.<br />I am pretty confident I will be able to get the engine running after all repairs...but I may need a new lower unit.<br />Anyone know where I can get, or have, a working lower unit for sale? (I would be happy to exchange my lower unit as part of the deal...mine would be fine for cosmetic restoration...it has a brass prop)<br />Thanks again for all the great tips! My sons (who are working on this engine with me as a Merit Badge requirement in Boy Scouts) and I are looking forward to getting this baby running one day!<br />-John (mvpvideo)

 

[mixerjv]

Re: 1957 Mercury Mark 55

Your best bet is to try to find another lower unit on ebay. Keep in mind there are two different models involved, long shaft or short shaft (driveshaft length is different). Transom heights of 20" or about 16" respectively. Lower units from Mark 35, 35A, 55, 55A, 58, 58A will work. There was a stud size change from 3/8" to 7/16" on those lower units mid 1959. I believe you can still use the newer larger stud size with enlarging holes on your mid section but I'm not entirely sure, check with Bob Grubb of oldmercs. If you can use the larger ones it opens up lower units from 1960 merc 300, 1961 merc 350, and the 1960-61 merc 400. <br /><br />If you end up wanting to rebuild your main problem will be obtaining the special tools. The water pump cartridge remover tool is impossible to replicate and very hard to find (although there is a chance you can fix the problem without removing the cartridge & driveshaft), some of the other tools have been replicated and appear on ebay from time to time along with some original tools.

 

[cobbler1]

Re: 1957 Mercury Mark 55

Laddies - the Mercury service manual does say that early 55E's were positive ground.<br /><br />The radio shack part number on the rectifier if needed is 276-1185

I have bought one of these rectifiers. Could you tell me how to wire it in?

Thanks,
Terry