Home › Forum › Ask A Member › 1955 Johnson 5.5 hp converted to single fuel line with pump puking oil or carbon
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Don.
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April 26, 2026 at 9:47 am #316519
out of the exhaust and coating lower case. What am I doing wrong other than running too rich?
April 26, 2026 at 11:37 am #316522Is your pump diaphragm ruptured?
When you squeeze your primer bulb there should be NO flow out of the vacuum pulse line.
April 26, 2026 at 12:12 pm #316528This is a 2-stroke, you WILL have a certain amount of unburnt fuel/oil mixture seeping. It can only be stopped by never running your motor.
So you need to make a decision, run it and accept it, or buy a 4-stroke.
The modern 2 cycle oil is designed to have much less environmental impact than regular motor oil used when the motor was new.http://www.richardsoutboardtools.com
classicomctools@gmail.comApril 26, 2026 at 12:25 pm #316530Which fuel pump are you using for your motor? 2-Stroke engines produce a stronger crankcase pulse than the typical 4-stroke engine does.
Many of the ultra-cheap fuel pumps on the market are copies of lawnmower type 4-stroke pumps and have been known to fail on 2-stroke applications.
If this happens…..raw fuel is pumped directly into the crankcase through the pulse line.
Can you post a picture of your pump?
April 26, 2026 at 5:03 pm #316561all these motor also have a dump route to flush accumulated fuel oil mix pooling inside the crankcase…
IF the purge route/ valve is blocked, purge channels blocked by your mod.to pump etc… fuel oil micx piles up in the crankcase especially at idle.
you need to run wot and the stuff will be ingested back into the cylinders but keep in mind that when “in ports” open incoming fuel oil juices also shoot out the “exhaust ports” & 30-40% fuel-oil gets dumped directly out by the bad 2 stroke design. at $4G US or 8$cdn it get expensive to be so wasteful. my 75hp ETEC burns .6 l of fuel/h trolling 🙂
A 0.6-liter amount goes into one imperial gallon about 7.6 times so in theory I can troll at least 7 hours on 160 oz of fuel.
for a US gallon 128 oz.. A 0.6-liter amount goes into one U.S. gallon about 6.3 times…..so figure 6 hours trolling
I doubt you could troll 6-7 hours with a 5.5 hp with 1 gallon !!
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April 27, 2026 at 1:48 pm #316637Seakaye12, No flow from pulse outlet on pump when fuel line bulb squeezed. The plugs are very wet so I am guessing that not being able to run in 13 gal bucket at WOT is allowing an accumulation of oil/gas in chamber to leak out the exhaust after the motor is shut down. I need to get a larger tank as I try to set up the carb properly before heading to the lake.
I am learning a lot about the 70 year old motors and I am 6 years older than my CD-12.
April 27, 2026 at 2:23 pm #316640Seakaye12, No flow from pulse outlet on pump when fuel line bulb squeezed. The plugs are very wet so I am guessing that not being able to run in 13 gal bucket at WOT is allowing an accumulation of oil/gas in chamber to leak out the exhaust after the motor is shut down. I need to get a larger tank as I try to set up the carb properly before heading to the lake.
I am learning a lot about the 70 year old motors and I am 6 years older than my CD-12.
You can dial them in pretty close in a barrel, but final tweaks should be on a boat, under load.
My 1956 30hp needs a change carb setting if I run it over in Ohio or Florida, it does NOT run the same both places…http://www.richardsoutboardtools.com
classicomctools@gmail.comApril 27, 2026 at 9:37 pm #316677I am learning a lot about the 70 year old motors and I am 6 years older than my CD-12.
all you need to know is in the FREE johnson bible…just download and print locally !
https://www.socalaomci.com/library/johnson_service_manual_10th_edition.pdf
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April 28, 2026 at 12:46 am #316689These motors called for a rich 16:1 fuel mix because of their design, which was using sleeve type bearings on the rods and mains instead of needle and roller style bearings. They also tend to run cold as they don’t use a thermostat to control engine temperature like the ’59 and later motors do.
A cold running motor can’t burn off as much oil as a hotter thermostat temperature controlled motor can so running it in a barrel is going to leave a big oily mess on the water and it will also run out of the exhaust onto the floor while being stored upright. It’s just the nature of the beast and wont be noticed much while running on a lake. Adding a bit of dish detergent to the water will help keep everything clean.
April 28, 2026 at 10:42 am #316722Dicks…..What is your history with this motor and two-stroke motors in general?
Specifically…..is this issue something “New” after the fuel pump conversion? Or; has the motor always exhibited these symptoms?
If your motor is firing on both cylinders and is tuned…..there should not be oil “puking” out anywhere. As others have stated….some unburned fuel is normal….especially in a barrel.
Is the carburetor dialed in? Are both cylinders firing?
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