Best oil for a 1955 mk 55

[mk55]

I have an excellent 1955 mk 55 with super compression. 135 on each cylinder checked withthrottle wide open and pulled over with rope.
I do not want to hurt this motor as it also runs around 40 mph on my 12 foot jetstreak and has a super hole shot with a redesigned prop.
What would you guys use for oil and at what mixture. I do get up around 5600 rpm wide open. i have been using amzoil racing 2000 at 50 to one for about an hour only. Should I go down in mix like 40 to one etc or try one of mercs oils. Thank you in advance for any advice.
In case you are wondering, my prop man has taken a 10 inch brass quicksilver and made a variable pitch on the bade 10 pitch to start with progressing to 12 pitch and then put a full cup on trailing edge all the way aournd the tip to just where the leading edge starts and then has that very sharp.
It is supposed to have the hole shot of a 10 inch pitch and then as it increases in speed the cupping and outer blade area starts to take effect.
It really works ausome and some of the merc guys all what to know where I got the prop as it no longer looks like a quicksilver.
Dave.

[Tom Foley]

Just use Merc or any other TCW-3 rated oil at 20 : 1 and you will enjoy a long life . I ran mine on Golden Spectro at 32:1 and it ran 77 mph on my Furnal Flyer . Some guys run them 16 :1 but my opinion is thats a bit oil rich. Thats a great motor but change lower unit oil after every two runs , both to keep clean oil in it and to monitor for water leakage into the oil .

[Mark75H]

change lower unit oil after every two runs , both to keep clean oil in it and to monitor for water leakage into the oil . I think that's a bit excessive with a std lower unit.

I agree, TCW3, maybe 32:1, but no leaner :)

[Tom Foley]

Yeah , that might be a little excessive but what the hell it only holds a few ounces ! Sam lets see some pics of your race stuff .

[Bruster]

so rich? This motor is exactally the same as the last 44 c.i. 40/45 and 50 Mercurys made, it's not a high performance motor and they have ran just fine @ 50:1 for years. 5,600 RPM does not require any extra oil. You're not doing anything good for your motor and the extra oil just adds to a pontential carbon issues such as sticking rings. What oil? Nothing but 100% synthetic :eek:

[Mark75H]

Even though it is the same bore and stroke, same block and same bearings - a 1955 does not have the oil recirculation lines and check valves used on the 50:1 motors that came out later

[Bruster]

....does this have to do with lubrication requirements? The recirculation system was engineered to recirculate fuel that falls to the bottom of the crankcase, rather than let it run out the bottom of the motor. Lubrication requirements are a factor of rotational speed. The more speed the more lubrication that's needed. Now lets factor the quality of todays oil to yesterdays (1955). Now explain why the need for 32:1 in a 5,600 RPM motor. :eek:

[Mark75H]

No, the collected recirc is routed to the main bearings .... it does have to do with lubrication.

Merc did not change their recommendations on the older motors that did not have the recirc system when they added the recirc stuff and proclaimed motors with it suitable for 50:1

[lilabner]

I used to have a article that covered oil problems wiht the Honda 125cc 6 cyl race bike. Although it was a four stroke engine, it used caged needle bearings to reach its 21000 or so rpm level..They had to put a drainage duct in the cages, shaped similar to a NACA duct, because the bearings pushed the oil so fast it would build up a wave of oil, and the bearings would skid if the oil couldnt get out. On one test session the engine wouldn't turn enough rpms, and the engineer finally discovered the cages were installed backwards..I found this article on AOL...referenced to an old magazine article, about 7 years ago..It was really interesting..the whole engine project is just amazing...125cc and 6 cyl, with 2 valves and point type ignition....over 21,000 rpm's....

I have often thought about 2 strokes running heavy oil mixtures and wondered if they might have a problem similar to this...might be a good topic for discussion since the history forum seems flat.....:confused:

Butch

[Bruster]

Now, now boys. Be nice. Let's not argue. I'm with you Bruster.

Hi Jim!
Got rain? :D Hope that's all. :cool:

No ones arguing, well at least I'm not, I'm just looking for hear the relevant facts, and I haven't seen them, at least here on this thread.... :eek:

[2us70]

Hey Butch, I will be down your way first of next week if we don't get another storm. I want to check out the Velocity. We have got to get some pictures of it running.

[lilabner]

Hi Jim..come on down..boat runs sweet, but I have to get a stock gear and different prop...hits limiter pretty quick with a 27 Mazco 3 blade with more to go..I guess a 2:1 gear ain't gonna get it..I want a 28 4 blade Mazco..right now I could use a 30...call me the day before and maybe we can go on a "road test"..


Butch

[2us70]

Sounds good to me.

[mk55]

How many of you are running a 50's merc at 50 to one synthetic, for how long and any trouble.
I just looked at the gallon of amzoil outboard bottle and it says do not mix any richer than 50 to one. Why would they say that.
To be safe I am going to use phillips synthetic at 32 to one. It says for all ratios from 20 to one and up. Dave.

[Bruster]

mk55 How many of you are running a 50's merc at 50 to one synthetic, for how long and any trouble.

Thought you would never ask. This little Merc has 2 speeds. Off and WFO with 50:1 Pennzoil 100% Synthetic. Ran Saturday just like it did the day I started it 3 years ago. :D


<img src=http://home.comcast.net/~mercmanwon/Jerry3.bmp>

[mk55]

How fast does that aristo craft go with the merc. Is that the 35 hp or the 45, I know I should know by the cover wrap but forgot which one is which.
Also what pitch prop are you using. Dave MK55.

[Bruster]

It runs 35 or 36 with the 44 inch Super Thunderbolt powerhead. I just pulled the 44 off and installed a 40 inch powerhead from a 350 Merc I'm restoring. It only runs about 30 now. :eek: I'll run a couple of tanks of fuel thru the 350, pull it off and throw the 44 back on. :D