Topic: 1955 5.5 Johnson fuel mix? – Antique Outboard Motor Club,Inc

This topic has 16 replies, 10 voices, and was last updated 4 years, 10 months ago by outbdnut2.

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June 9, 2019 at 3:28 pm #176954
jimk
Participant
I have a 1955 5.5 that i brought back to life with new points,condenser,coils,waterpump,carb kit ect. My question is what mix to use. I think its supposed to be 16:1 and was told I could run at 24:1 with newer oils like the Johnson tcw lll. Now I would like to keep it running for many more years so opinions are welcome from the pros here. I ran it today with a mix of 20:1 and it runs great on my little 12 ft boat but not sure whats best. Thanks for any advice! Jim
June 9, 2019 at 3:37 pm #176958
amuller
Participant
I use 24-1 in mine.
- This reply was modified 4 years, 10 months ago by amuller.
June 9, 2019 at 4:21 pm #176959
bobw
Participant
US Member
I run 16-1 in my ’54 5.5 per the original factory recommendation. Modern TCW oils burn a lot cleaner and probably do offer a higher degree of protection but I figure oil is cheap in the overall scheme of this hobby.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
June 9, 2019 at 4:34 pm #176960
jimk
Participant
At 16:1 do you have any plug fouling? I am not worried about the cost for just a bit more oil but would like to avoid changing plugs out in the middle of the lake. If all is ok I wouldn’t mind using the factory recommended amount. I also use premium gas as thats all I can get without ethinal in it.
June 9, 2019 at 7:08 pm #176963
bobw
Participant
US Member
No plug fouling at 16-1 with modern TCW oil.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
June 9, 2019 at 10:18 pm #176978
garry-in-michigan
Participant
Lifetime Member
The OMC 5.5 and 7.5 horse outboards that era had counter weights riveted to the crankshaft to promote a smoother idle. This required part of the connecting rod be cut away to clear it. The bottom rod is trimmed on the bottom while the top rod is trimmed on top. The channel in the upper part of the connecting rod that collects oil and helps lubricate the rod bearings is missing on these top rods. The use of the four gallon tank lightens the load and also compensates for the less oil getting to the rod bearings. This is why both six and four gallon tanks take a quart of oil.
The newer oil has advantages. It lubricates better and burns cleaner. It also has disadvantages. It doesn’t seal the crankcase as well. Outboards without seals (like the 5.5 & 7.5 classics) can loose crankcase compression from worn bearings. Some antiques require SAE 40wt. oil for proper seating. Allso, the film left on the bearings evaporates over time which means a fogging oil must be used for long term storage.
- This reply was modified 4 years, 10 months ago by garry-in-michigan.
June 9, 2019 at 10:34 pm #176982
garry-in-michigan
Participant
Lifetime Member
Why is my post disappearing when I hit the [submit] button ? ? ?
June 9, 2019 at 11:06 pm #176985
Mumbles
Participant
Sticking with the factory recommended 16:1 will help you sleep easy tonight. The reason the 5.5 and 7.5 OMC motors of this era need the rich mix is because they don’t have any needle, ball, or roller bearings in them, only sleeve type friction bearings which need the extra lube. Running them at high speed with a leaner gas/oil mix runs the risk of starving the bearings for lube and that in turn makes the crankcase too small for the connecting rods as they can seize on the crank and then break through the side of the block leaving you stranded without a paddle.

As stated, this topic can go on forever but when you think about it, these motors have probably lasted this long because of the amount of oil they drink. If the motor is well tuned and has decent compression, they will hardly smoke at all using modern TCW III oil. Smoke from any two stroke motor is usually more noticeable on startup, when the motor is cold, but goes away as it warms up.
June 9, 2019 at 11:13 pm #176989
Mumbles
Participant
garry-in-michigan wrote:

Why is my post disappearing when I hit the [submit] button ? ? ?

I don’t know why but mine was doing the same thing the other day over in Dockside. It finally posted by opening a duplicate window and backing up to copy/paste the original text before the gremlins found it again. Later on I found the missing posts marked as ‘hidden’. Never did figure that one out.
June 9, 2019 at 11:14 pm #176990
bobw
Participant
US Member
Very well stated by Mumbles. This series of motors was prone to throwing a rod through the block without adequate lube oil. As he stated, even at the 16-1 ratio they will smoke very little once properly tuned and the carb is dialed in correctly.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
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