Oil for 1958 Mark 78E

[imported_Skippy]

Comment: purged for not agreeing with the elders

 

[emckelvy]

Re: Oil for 1958 Mark 78E

Pretty rich oil mix, it could have led to heavy carbon deposits on the rings and ring-sticking. Definitely a carbon-cleaning treatment with Seafoam, OMC Engine Tuner, etc is in order.

Seeing as it runs well, it may still be in decent shape inside. I'd do compression checks before and after Seafoam treatment and see what it looks like. If you get no more than 5 psi variance between cylinders, she's a tight motor. More than 10 psi and I'd start worrying. A leakdown test will tell you a lot more than simple compression test, that' s fer sur.

BTW a good grade of TCW-3 oil mixed 50:1 with unleaded, non-alcohol regular gas will work fine in your motor. I'd throw some Seafoam in the fuel (for the first few tanks at least) for good measure, too.

HTH & G'luck with your DockBuster!..........ed

 

[imported_Skippy]

Re: Oil for 1958 Mark 78E (long!)

Re: Oil for 1958 Mark 78E (long!)

Ed,
Thanks for the reply!

 

[Scaaty]

Re: Oil for 1958 Mark 78E

I wouldn't even go to 50-1. Just go ahead with TCW at 24-1......I'm surprised its that clean with 30wt ND. Thing is motors haven't changed much, but oil sure has. Tearing down a 58 Merc30 now....fulla carbon crud

 

[steelespike]

Re: Oil for 1958 Mark 78E

I did a little research 30 non detergent was kind of the
lowest choice thus it is 16:1 78E is listed at 20:1 with
Formula 2 Quicksilver oil.The powerhead has lots of ball and roller bearings but 2,center and 6 mains are bushings on all 6s to 1970,Though later 6s are rated at 50:1 with Formula 50 Quicksilver oil,according to my references.
I'm sure modern oils will stand up as well or better than the old 50 Quicksilver
Some of the 6s are sensitive to proper timing adjustmemts and octane ratings.
You might go over to Johns Old Mercury Web Site and ask on their forum.I'm sure they can steer you in the right direction.
An excellent Merc site with great info and links.

 

[Paul Moir]

Re: Oil for 1958 Mark 78E

Think of it this way. TC-W3 is basically 30 weight non-detergent with a bunch of stuff thrown in since it exclusively goes in outboards. Things like corrosion inhibitors, deposit controllers, stuff to make it like to stick to the engine's internals, etc. So why on earth wouldn't you use it?

As for ratio, I've heard the older, larger Mercs work just fine on 50:1. But I'm no expert on them so I'll leave it to those who are.

Finally, 350 hours is absolutely nothing on an outboard as far as wear goes. So you're not necessarily "messing with success". It's certainly conceivable (though I really doubt it) that you've lost 1/2 the life of it by running 30w n-d.

 

[Laddies]

Re: Oil for 1958 Mark 78E

24 to1 anything else is BS the powerhead is completely ball or roller brgs but if it is alittle lean on top end they would even cook at 24 to 1 it's good insurance to run the ratio that was recommened by the manufacturer

 

[emckelvy]

Re: Oil for 1958 Mark 78E

I ran the living Tar out of my old M700 Dockbuster back in the Eighties, on 50:1 TCW-2 (or whatever the latest grade was at the time), water skiing flat out with deep-water slalom starts and the motor never missed a beat.

BTW if you're using 24:1 in a fixed-main-jet motor, you're actually running a leaner fuel-air ratio than on 50:1 mix, so how does running twice as much oil help fight lean mixture?

Running 50:1 with higher-quality oil would certainly provide at least as good (if not much better) lubrication than the richer-mix old oil, with the added benefit of a slightly richer fuel-air ratio.

I can see maybe 40:1 just because she's a bit long on years, but the innards of the 70 HP are identical to the ever-popular 50 HP 4-cylinder and there's millions of them running just fine on 50:1 mix.

I defy anyone to tell me the difference between the "fully jeweled" larger Merc motors that were running with rich-mix, Pre-Quicksilver oil, and those same "fully jeweled" larger Merc motors which were recommended to be run on 50:1 Quicksilver mix when it was introduced (around '62 wasn't it, if I recall?).

Skippy, a 'gentle' treatment of Seafoam, i.e. adding 1 oz per gallon of gas, isn't going to hurt anything. If your compression readings and leakdown test come out OK, and you want to go "low-impact", a gradual introduction of Seafoam won't have any deleterious effects. But it will help clean out any accumulations of carbon on the piston land/rings.

One thing to avoid if at all possible is gasohol, not good on old hoses/seals/carb parts/etc.

She'll run nice and clean on TCW-3 and regular unleaded.

BTW I set up my ol' 700 with a dwell plate and it always idled and started up great. Not bad for a $25 motor back in 1983! You don't find too many like that anymore!

Enjoy...........ed

 

[imported_Skippy]

Re: Oil for 1958 Mark 78E

Many thanks to all those who responded !

 

[Scaaty]

Re: Oil for 1958 Mark 78E

Just where do come up with this theory?

BTW if you're using 24:1 in a fixed-main-jet motor, you're actually running a leaner fuel-air ratio than on 50:1 mix, so how does running twice as much oil help fight lean mixture?

Give me a break. Running 50-1 is about 2.5% oil. Running 24-1 is running 5% oil.......means little if nothing in leanness. And oil burns too. Plus although the motor is all ball or roller bearings, the pistons just love that touch of oil between them and the walls. The rollers on the crank and rods could live on 100-1 probably, end cap rollers probably 200-1. Its keeping the pistons and rings oiled and as cool as possibly that counts.

Running 50:1 with higher-quality oil would certainly provide at least as good (if not much better) lubrication than the richer-mix old oil, with the added benefit of a slightly richer fuel-air ratio

Less oil is better lubrication? The oil today is not much diferent than the old days either....still comes out on the same hole in the ground. Its the additives that have changed (not talking SYN here).

 

[emckelvy]

Re: Oil for 1958 Mark 78E

OK, then WHY are so many of the "newer" motors running just fine on 50:1?? Including MILLIONS of 50 HP 4-cylinder Mercs which are virtually IDENTICAL on the insides to the MK78? I know for a fact that they're using the same piston rings so your'e saying 50:1 is no good for a MK78; why should it then be any good for the newer engines?

The thing about using more oil than you really need is that you're also going to build up more carbon on the innards. Seen plenty of Mercs with burnt up pistons/rings as a result of carbon buildup from poor quality/too much oil.
Thank Goodness for Seafoam!

BTW tuning by adjusting oil mix is NOT a theory. Albeit the diff may be slight in recreational use, but we're all cutting hairs here with the oil mix aren't we.

More fuel/less oil= a richer air/fuel mix and the converse is true; Less fuel/more oil= a leaner air/fuel mix. By saying that "oil burns too" you're implying that oil burns with the same energy output as gasoline? Ludicrous!

And the additive packs in "modern" outboard oils are Certainly way better than 1950's HD30 oil or the mfr's never would have went to a leaner mix.

I recommend Scrappy upgrade his MK78 to EFI and Oil Injection, that'd cure the issue fer sur! :devil:

Just my .02.........ed

 

[emckelvy]

Re: Oil for 1958 Mark 78E

Sorry, I meant Skippy!:^

By now we've probably confused Skippy with our rants; Skip, just run what makes you feel good and if you want to experiment later, mix up a small, trial amount at whatever ratio you like and see how she runs; change the ratio a bit and see if you note any diff.

This motor is probably not so sensitive to those kind of changes anyway, it's not really that high-strung. Maybe what kept the innards in such good shape all these years.

 

[AMD Rules]

Re: Oil for 1958 Mark 78E

Where's Lubedude when ya need him....lol

 

[Laddies]

Re: Oil for 1958 Mark 78E

Ed, take a chill pill like I did when I saw you responce this morning, I thought better to not respond and keep the argument going, it don't matter to me what oil or or ratio you use of have used. He ask what the manufactures recommended I thought and posted Mercury Marines oil recommendation, like any mechanic would. A Mark 78 was a high compression 66 cu.in. engines and by the time Mercury when to 50 to 1 engines the Inline 6s were 90 cu.in and most use a richer high speed, again this is not from me but Mercury Marine. As far a a richer fuel mix runnig leaner, get real. You harp on the 4 cyl 44 cu.in.engines, if your theory is right then expain why Mercury Marine recommended the 44 XS racing engines powerhead, that are part for part interchangeably with with the 4 cyl fishing engine are ran with a 25 to 1 mix and a smaller main jet. In 40 years of racing we have never had to decarb a engine and won several National Championships. If you use high quality oil they don't need to be decarbed and you can drink your Seafoam maybe it will flush you out

 

[Scaaty]

Re: Oil for 1958 Mark 78E

OK, then WHY are so many of the "newer" motors running just fine on 50:1?? Including MILLIONS of 50 HP 4-cylinder Mercs which are virtually IDENTICAL on the insides to the MK78? I know for a fact that they're using the same piston rings so your'e saying 50:1 is no good for a MK78; why should it then be any good for the newer engines?

Good Lord. I'm a retired a First Class Journeymen Machinist (professionally for 21 years). Wrenched all my life. Same piston rings my A$$. Metallurgy has changed so much in JUST THE LAST 5 YEARS, it would make your head spin. And the tolerances are a LOT closer, BUT the metal does not expand the same as the old ones, which were built pretty loose to begin with. You ever have one of these motors apart? Heres a pic of a 62 Merc 450 I just pulled apart, trying to see what could be saved. Pistons were junk. Look at those rods in the middle. Pretty colorful dude, and its HEAT. Not enough oil did this. I might ebay this stuff, as the parts are hard to come by, and these can still be used. And I'm now pulling a 58 Mark 30 down, and have a good look at those parts too, maybe a salvage. At least the thing still spins (kinda). If ya want to argue with people here, well go ahead. Like saddling a cow. Lots of work, but whats the point.