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Johnson FD-12 18hp 1958 convert 2 single line fuel sys

C

Customan

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Converting the pressure fuel system to vacuum:
Mukumi makes plastic and metal pumps and I happen to have the plastic one! Is there anyone who has done this? and is one pump any better than the other? The process looks fairly easy, but I'll explain the proceedure and if any dought out there please contact me...
Remove the (2) two rubber flaps on the lower Leaf/Reed Plate (this is behind the carb.) and plug (1) one of the two holes (useing a vacuum cap) leaving the other hole open. The open hole now gives you a PULSE VACUUM as needed for the vacuum pump to function! Again, all suggestions are wellcome.

 
You do this the hard way. I just drilled & tapped one of the bypass covers and screwed an elbow with a barb in to it. Put a pipe plug in the old pressure line outlet and presto, Pulse Vacuum. No messing with the manifold. (1957 18hp Johnson)

Sierra fuel pump 18-7353 works perfect for this conversion - $45
 
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Since the carb was getting rebuilt and re-gasketing the manifold this was the perfect time to convert the fuel sys. to single line. vary simple, no drilling, no taps, no fittings, use the same factory pressure fitting now pulse vacuum..! check this link. http://outboard-boat-motor-repair.com/johnson/Pressureized%20Fuel%20Tanks.htm (you may have to cut and Paste this link..) Let me know what you think about this method.. Thnks
 
I've done two tapping the bypass cover/plugging hole method. Doing a third as we speak. I use a mikuni single feed pump $20.00. I use a tiny inline filter, remove the old filter and mount the pump there. Of coarse, I have to buy a fuel connector, but now all my motors have the same connectors. I might go from a '58 to a '63 to a '72 to a '59 year motor.
 
farnsp said:
I've done two tapping the bypass cover/plugging hole method. Doing a third as we speak. I use a mikuni single feed pump $20.00. I use a tiny inline filter, remove the old filter and mount the pump there. Of coarse, I have to buy a fuel connector, but now all my motors have the same connectors. I might go from a '58 to a '63 to a '72 to a '59 year motor.
Click to expand...

I had seen those metal type mikuni pumps but in my case they sold me a plastic mikuni pump used on mowers tipicaly on 18hp johndeer! Do you think this will give me the same performance or longevity ?
 
Not knowing who "they" are, I would say that the volume of fuel should be ok. Plastic vs. Metal... an outboard on a small boat, things could get pretty violent... I like metal. A round plastic pump might be more shapely, and fit into tight spaces better. Who knows, it could be a blessing.
 
Thanks for the reply, I am still waiting on some misc. parts to arrive, so hopefully bye this weekend it should be buttoned up. I be sure to send you the pro's and con's of this project.
 
farnsp said:
I've done two tapping the bypass cover/plugging hole method. Doing a third as we speak. I use a mikuni single feed pump $20.00. I use a tiny inline filter, remove the old filter and mount the pump there. Of coarse, I have to buy a fuel connector, but now all my motors have the same connectors. I might go from a '58 to a '63 to a '72 to a '59 year motor.
Click to expand...

Looking at my motor, I guess the left side there are (2) removable cover plates, are these the by-pass covers your talking about? Trying to keep my options open in case one doesn't work! And if so does it matter what plate you tap?
Thanks
 
Thats right, two plates- four screws per plate. theres a hole about 5/16" generaly in the center. I drill and tap (1/8 pipe tap) the top one just to make it easier to connect hoses. Take the bypass cover off when drilling, Use a new gasket if the old one tears. I'll try to get a picture for ya.
 
You can see the hose barb threaded into the bypass cover. Then theres the plug in the block where the tank airline used to attach.
 

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I like to replace the cover with a newer unit and install the original type fuel pump in the upper cyl. It may be just because I have lots of used parts around. I really like the old pressure system but now the fuel hoses and ends are so expensive. I do have lots of good tanks around here, however.
 
Here's the pump in place. The air line is going through a hole I drilled through the started bracket. This allows for alittle bit more room. You can see the black air line running over the head.
 

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Been out of town, The pictures look great, looks professionally done. Well all my parts are in so monday I'll spend the day on it. I will shoot pics of mine since the carb. and reed plates are off and the pulse vac. at the reed plate(hopefully working)pending plan "B" your method! Thanks for the great info......
 
Irishw.m. I would start another thread in this forum. As it is now your post is burried and wont get the looks you want. I've looked at the model and year of your motor, and it looks like it does not have all roller and needle bearings, thus the fuel should be mixed 24:1 with good outboard oil to 87 octane gasoline. You can also search this subject at the top of this page. Search " fuel mix 1959 10hp "
 
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