Gas / fuel leak help on a 1954 25hp Johnson RD-15

[jdean]

I also found this thread on the same topic, of re-capturing oil/fuel mix.

https://www.aomci.org/forums/topic/unburned-fuel/

I’m still looking for a picture or explanation of where exactly to drill the hole to fit the barbed fitting, and what has been used to plug the existing hole.

[crosbyman]

seen photos of the purge valve body being modified with JB weld if I recall the collector nipple was installed in it while the internal passage to drain out was blocked off.

in essence a new route was create to drain out the oily stuff

Joining AOMCI has priviledges 🙂

[jdean]

Crosbyman, I ran across this thread just a few minutes ago…

https://www.aomci.org/forums/topic/unburned-fuel-oil-recycling-mod/

I believe the above post is what you were talking about. It was very helpful.

I’ve started collecting the necessary parts to make this modification. It seems like the only responsible way to run this 1954 motor, especially after seeing the trail of rainbows behind my boat when idling out of the marina! Yuck!

I will post pictures are results in a couple of weeks when I have this working. 🙂

[crosbyman]

glad you found it … I searched the duckworks site to no end but at least those pictures give you the basic approach.

IF you install a pump and oil recirculation set up you could probably use the same 2 line side connector instead of replacing it. the “air” pressure nipple on the back of the carb becoming useless simply route the new ” oil” line to the dual line connector “air” side and the oily mix will get back into the tank. 🙂

just a suggestion…

I am almost tempted try this on a nice 1959 Golden Jubile 5.5 hp and a Johnson I have in the basement and waiting for winter to come around 🙂

Joining AOMCI has priviledges 🙂

• This reply was modified 3 years, 5 months ago by crosbyman.

[jdean]

I found two additional relevant posts to this discussion that should be linked here.

This post has a great discussion of how the issue of excess crankcase fuel was dealt with over the years. Very informative.

https://www.aomci.org/forums/topic/question-for-fr/

This next post showed detailed pictures of a few engines and how the drains worked, and how the design was changed over time.

https://www.aomci.org/forums/topic/omc-22-cubic-inch-25-hp-differences/

[jdean]

I am pleased to report that I have successfully re-directed the excess gas from my exhaust into a container. I have also changed over to a full-synthetic oil. I can’t BELIEVE the difference this makes! I should have taken pictures of the water in the trash can after idling this motor for a while before switching to synthetic and modifying where the unburned gas goes. GROSS!! Now it looks like you could drink it. Ha ha.

So this is what I did. I bought part 302033 on eBay for just under $8. That way, I could always go back to stock if I screwed something up, or if I want to sell the motor stock.

It had some ridges on it where I wanted to put my nipple, so I filed them off. I drilled and tapped the hole to match the 10-32 threads on the nipple. The resulting piece looks like this:

I bought a Beswick Engineering nipple elbow on eBay for about $7 that was kind of like a miniature banjo fitting. It is a 90 degree fitting with an o-ring up against the mating surfaces. It also allows you to adjust the elbow to any direction that you want when you tighten it down. Very convenient for this application. I wanted to use 1/8 fuel hose from O’reilly Auto Parts to match the 1/8″ holes in the engine block, and this fitting was perfect.

I used some epoxy to fill the drain hole to the exhaust.

It all seemed to fit together nicely. I painted the cover plate, and put the gas line on the elbow. It fit incredibly tight and I could hardly get it off again. I screwed the elbow onto the cover plate and installed it on the motor.

I zip-tied the new 1/8″ line to the nearby quick-connector so it wouldn’t get yanked out.

Initial tests are fantastic!! I have attached a video of my motor idling and the amount of gas coming out of the hose.

Now I just need to get a more appropriate container and go try this out on the water. Thanks again for everyone’s help!

https://www.youtube.com/shorts/Saq7ETFo8u0

• This reply was modified 3 years, 5 months ago by jdean.
• This reply was modified 3 years, 5 months ago by jdean.
• This reply was modified 3 years, 5 months ago by jdean.

[crosbyman]

nice work I am convinced my friend 5.5 needs the same surgery,

With all that fuel coming out up front but I am a bit worried seeing you took out the purge valve itself in the picture anyway.

was it not required to prevent the loss of vacum on the up strokes ?

the valve is needed to push out residual fuel/oil but needs to close shut keeping maximum upstroke crankcase vacum build up to suck fresh fuel/oil into the cylinders .

as it stands now you may be allowing to much fuel/oil mix to be sent into your external bottle on the down stroke instead of 95% of that downstroke crankcase pressure pushing fresh fuel oil into the cylinders .

or did I miss something ?

Joining AOMCI has priviledges 🙂

• This reply was modified 3 years, 5 months ago by crosbyman.

[jdean]

I filled the hole going to the exhaust with clear epoxy using a toothpick.

I put the purge valve back on before I put everything back together.

I read in another post that there were screens in the valve that needed to be cleaned periodically. Based on the paint on the purge valve cover, it had possibly never been removed. I carefully removed the purge valve to see if there was anything in there that needed to be cleaned, and didn’t find any screens, or anything like that. Just very small holes into the crankcase. I left the purge valve off when I was applying the epoxy. It was in such tight quarters, and I didn’t want to get epoxy on it. Yes, I put the purge valve back on exactly how I found it when I was done.

[Mumbles]

Now you need a two line tank so you can feed that excess fuel back to the tank, and keep it all original looking!

[jdean]

I do like the idea of feeding the gas right back into the tank! I think I’m going to run it as-is for a while and monitor what is coming out of the tank before making that modification. I am not opposed to adding a fuel pump, and changing this over. That sounds really slick.

Would you recommend using a fuel filter on the fuel line going back into the tank, or should it be okay raw?

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