Double to Single Fuel Line Conversion

[58CorrySuburban]

Hi,

When I first read the article (here @ Iboats) I thought I understood it, but when I looked closely I became unsure.

It apears that you tap the two outer holes for securing the pump (on the upper bypass cover), and drill out the center hole.
This is followed by a picture of the pump screwed onto the bypass cover (in this picture the pump is directly over the cover).
But in the picture of the completed project it apears to span both the upper and lower bypass covers?

Can anyone clarify the conversion process?

 

[samo_ott]

Re: Double to Single Fuel Line Conversion

What you said is correct. The pump mounts to one bypass cover only. In the pic it looks funny as the pump hangs down in front of the other bypass cover but does not connect to it in any way.

 

[asdasc]

Re: Double to Single Fuel Line Conversion

I think the confusion comes from the 3rd photo from Tashasdaddy in the FAQ. He has the pump mounted on the cover, or sitting there, but not in the final orientation. In the last photo he has showing the finished install, it looks like he rotated the pump 180 degrees to the cover compared to the 3rd picture.

 

[tashasdaddy]

Re: Double to Single Fuel Line Conversion

asdaxc, you are correct, on the newer motors the pump would mount as the 3rd picture, but the 5th pictures is the way it mounted on that motor, because it would not clear the timing linkage and timing plate. so i just turned it 180 degrees, it is mounted to the top bypass cover, see phillips mounting screws.

 

[58CorrySuburban]

Re: Double to Single Fuel Line Conversion

Thanks,

Noting the phillips head orientation made it click for me. I'm new to outboards, so I'm easily thrown off. The 180 deg. flip flop and final change during reinstallation had my brain in a knot.

It's only because of you guys that I even knew it was an option to make the conversion in the first place. So, once again, thanks again.

-Josh

 

[F_R]

Re: Double to Single Fuel Line Conversion

Tashasdaddy go lucky in his installation with the pump upside down. I didn't realize it myself till just recently, but the pump can get a big bubble of air in it and fail to work if mounted upside down.

There are other pumps that will mount right side up on the upper cover and still clear the linkage. 380016 is one.

 

[tashasdaddy]

Re: Double to Single Fuel Line Conversion

i never had a problem with it. but i sure you are correct.

 

[asdasc]

Re: Double to Single Fuel Line Conversion

Did anyone happen to save Flyboy's pictures of the conversion on an 18HP? In the FAQ he links to pictures that are no longer there. It would be really nice to have those as well.

 

[tashasdaddy]

Re: Double to Single Fuel Line Conversion

it has been deleted for his photobucket page, he also has not posted in over a year.

 

[jay_merrill]

Re: Double to Single Fuel Line Conversion

Here's how I converted a pair of 1958 ERude Bigtwins. One was done by using a bypass cover off of a Johnson 33hp and the other by drilling/tapping the original bypass cover.

The original bypass covers had mounting bosses for a fuel pump because the Gale version of the motor came with one. That pump, however was different than what is available today, and those mounting bosses are very slightly higher on the face of the cover, than the later covers. If you try to mount a currently available pump on the top cover, right side up, the peak of it will hit the throttle control rod, which is located just under the armature plate. Unfortuneately, the pump also can not be mounted on the lower bypass cover, because it won't clear the bottom portion of the cowling.

As for running the pumps upside down, I can only say that my ERudes were run for hundreds of hours with the conversion and I never had a bit of problem with the one that was mounted that way. If the OP is converting an 18hp motor, I do agree that the 380016 pump, which is now a 388685, should be a better choice. Since this size pump was used on the "through-the-hub-exhaust" models of the OMC 15hp motors for years, it should deliver enough fuel for the 18hp motor. Whether it would for the 35hp motors I don't know, but the larger pump was the one that was recommended to me.

BTW, the red wire is a lead for a Tiny Tach inductive tachometer, I moved it after these photos were taken just because the location next to the fuel lines made me nervous. I don't think that there is a significant amount of voltage or amperage running through the wire, but I took a "just in case" view of it.

 

[F_R]

Re: Double to Single Fuel Line Conversion

380016 was also used on 40hp motors.

I am not claiming the pump cannot work upside down. Only that it might not work if it gets an air bubble in it. Here is why: The fuel outlet is normally at the top of the diaphragm chamber and any air bubble is expelled out the outlet valve. Turn it upside down and the outlet valve is at the bottom of the diaphragm chamber and the chamber can fill with air from the valve upward and nothing forces it down and out the outlet valve. If that happens, the diaphragm can just flutter back and forth in air (which is compressable). If the diaphragam chamber is full of fuel, the diaphragm works against uncompressable fuel and the fuel has to move if the diaphragm moves. In other words, it can and may work but is not the most reliable way to mount it.

 

[58CorrySuburban]

Re: Double to Single Fuel Line Conversion

Ok, I see.

So I have a 1958 (19-C 1957 "hold-over") Evinrude Bigtwin 35hp, what parts should I order to avoid the up-side-down issue?

From the looks of it my motor is the same in project area, but are there any differences/acceptions to watch out for?

Josh

 

[F_R]

Re: Double to Single Fuel Line Conversion

Here is a 40hp with factory set-up 380016 pump. Also a '58 35hp with factory pump conversion kit. (The '58 pump is obsolete, but a 380016 replaces it).

 

[jay_merrill]

Re: Double to Single Fuel Line Conversion

F_R, help me out on something - I looked up the 380016 and found a photo of it, which was one of the smaller, square shaped pumps. Am I mistaken?

My thought with the 18hp conversion is that the smaller pump would work fine because it was used on many of the later model 15hp, thru-the-hub models. On the larger motor, I'm not sure it would deliver enough fuel. I actually thought of mounting two of the smaller pumps on my Bigtwins, with Y-connectors on each side. Part of the attraction was having redundant pumping (its the airplane mechanic in me!), while the other thought was merely to make something fit. In the end, I didn't do this because it just seemed like too much complication and I wasn't sure that the bottom pump would fit anyway.

 

[1946Zephyr]

Re: Double to Single Fuel Line Conversion

Ahhh, yes. I will be doing this same conversion on a 1954 Big Twin, soon enough. The same pump is great, because it won't interfere with the outer shroud.

 

[jay_merrill]

Re: Double to Single Fuel Line Conversion

Just a tip on the '54 motor - I think I remember a post in another thread about this subject, saying that the older BigTwins don't have the mounting bosses molded into the bypass covers. I believe that post also indicated that the bypass covers on the older motors, have a different shape than the ones on the 35hp Bigtwins, so you can't swap them.

Perhaps F_R, TashasDaddy, Ezeke, or some of the other guys, can offer comment on this. My memory is a bit fuzzy on the issue, but I am pretty sure that was the case.

 

[1946Zephyr]

Re: Double to Single Fuel Line Conversion

ahhh, that sucks. Well, maybe I'll find another way. Like maybe the fuel pump style that the '59 35's used, instead of the newer style.

 

[tmcalavy]

Re: Double to Single Fuel Line Conversion

Some of us have successfully done the conversion using a Mikuni snow mobile fuel pump...did this on my 57 E-rude Big Twin. No problems so far.

 

[F_R]

Re: Double to Single Fuel Line Conversion

OK, as for the 380016, I was aware that the number had been changed but had never followed through to see what the new one is. Sure enough, it is the small pump. So I wonder myself whether or not it is enough for a 40hp. I still have a NOS 380016 so I haven't tried a small one on a 35 yet. However, the 380016 was stock on 40hp motors and BRP says the small one will replace it, so.......

As for the 25hp, if you can be so lucky as to find a bypass cover from a Gale motor, it will have the pump holes. But there is another way. Here is a picture of a conversion that I helped a guy make on his '54. I made an adapter plate to stack on top of the original bypass cover. The pump mounts to the adapter and the bypass is drilled to allow the pulses to get to it. The bypass on a 25hp has big bumps on it so he sent it to me and I milled it flat so the adapter seals to it. The ridges on the adapter are not for real, that's a light distortion. That is a standard Sierra pump you are looking at. The plastic hoses are his doing, not mine.

 

[1946Zephyr]

Re: Double to Single Fuel Line Conversion

F_R, thanks for your input. Fortunately, I work in a mchine shop, so I should be able to accomplish this.