Winterizing a Merc Mark 78

[JohnRuff]

This is an in-line 6 cylinder and a two cycle. The oil to gas ratio is 24 to one not 50 to one. <br /><br />The motor will be garage kept all winter and will never get near the freezing point.<br /><br />With all that oil in the gas mixture - and having run the carbs dry already -- do you think I need to fog the pistons for winter storage?<br /><br />I live in Phoenix Arizona land of low humidity.

 

[Laddies]

Re: Winterizing a Merc Mark 78

To properly fog that engine or any 2 cycle you need to run the fogging mix thru the carbs to protect the bearings we mix a fogging solution in a fuel tank and while the motor is warm just run it through the carbs loading the engine up with the choke as we run the carbs dry

 

[mixerjv]

Re: Winterizing a Merc Mark 78

In all honesty with your low humidity you'll probably be fine if you just leave it as is, but it certainly wouldn't hurt to do a proper winterization as Laddies points out.<br /><br />BTW, 24 ratio is not needed, that was for older two cycle oil made in the 50's or 60's, you'll be fine on a 50 to 1 and probably run better with modern mercury two cycle oil. I've run my Mark 58A on 50 to 1, no problems.

 

[Laddies]

Re: Winterizing a Merc Mark 78

24 to 1 motors were designed to run at that mix it has nothing to do with the oil it has to do with the brgs. the older tolerances were not as percise as the newer engines. If you want that 78 to live don't skimp on oil--Bob

 

[emckelvy]

Re: Winterizing a Merc Mark 78

That Mk 78 has no different bearings than a later model 700 Dockbuster or for that matter any 60's or 70's vintage Merc 500 4-cyl. The 70-HP six has the same bore and stroke as a MK 58 or M500, just 2 more cylinders. <br /><br />The reasons for 24:1 or richer oil mix are varied and do include the motor's design, but the main reason was the lubricating characteristics of the older oils.<br /><br />I ran the living tar out of my old M700, on 50:1 mix of the older rated TCW or TCW2 oil and never had any reliability problems. No diff between that powerhead and the MK 78.<br /><br />Regarding the 50's Merc motors not being built to 'precice' tolerances, IMHO these Fully Jeweled motors were way ahead of their time and are more 'precise' than Many newer motors.<br /><br />I'd have no trepidation about running that MK 78 on 50:1. Just use a good premium mfr's oil, or Penzoil Synthetic Blend (I still get it at Wal-Mart for around $10/gal). Funny thing is, Penzoil used to be like DEATH to the motors (i.e. massive carbon buildup) but this new stuff seems pretty good.<br /><br />Now, I'll grant you there are MANY motors that will not tolerate 50:1 and MUST be run with a richer oil mix (such as most antique motors and 50's/early 60's era Johnrude 3's 5.5's, 7.5, to name a few with babbitt bearings), but a Fully Jeweled Merc MK 4-cyl or 6-cyl ain't one of them!!!!!<br /><br />BTW, with the motor on its back you could pour a couple of teaspoons or so of light oil down the throat of each carb and then pull the recoil thru a few times to distribute the oil. Then flip it over with the spark plugs out, pour oil down the cylinders and rotate the crank with the plugs still out. That should at least get enough oil inside to keep any stray moisture at bay.<br /><br />Cheers.............ed

 

[Laddies]

Re: Winterizing a Merc Mark 78

Jeez Ed, I was only repeating what was said by a Instructer in Merc school in the mid 60s didn't know it would start a war of words. I wouldn't tell anyone to use a lesser mix than the factory recommends, that was my only point I know that there are lot of pre 64 engines out there running around on 50 to 1 I also know of some that died from it, so as a professional marine mechanic I couldn't give the advice some of you do--Bob