Pressure tank to single line, 1957 18hp Evinrude

[cr9c1]

I'm converting my 1957 Evinrude 18hp from the 2 line pressure tank to the single line as I have a myriad of the single line tanks kicking around that are in great shape, and the pressure tank that came with it has rusty innards.

I used the instructions found for the 5.5hp, using a vacuum cap to block off one crankcase port behind the intake manifold, and using that as a source for vacuum. I picked up a rectangular pump very similar to the Mikuni that seems to be the choice of everyone's conversion.

I had a couple questions. I was going to replace the glass bowl with an inline filter. However, I haven't gotten around to it, and for the sake of getting it running with what parts I have, I'm just going to use the bowl. Now, should i hook the pump up before the bowl, or after the bowl? Meaning, line from connector on outboard goes to bowl first or pump first? For obvious reasons it would make more sense to go with bowl first, as it will keep some stuff out of the pump (it has a filtering stone or something in it)

My 2nd question/issue is it seems that the pump isn't doing anything to speak of. I primed it up, and looked for leaks and heard the fuel going in to the carb bowl (had my ear to it) and it shut off and the bulb got hard like it should, however after several attempts at starting it, the bowl was dry. I know the theory of how vacuum fuel pumps work but have no idea how to actually see if it is..

3rd and final question/issue: Will the small pump supply enough fuel to feed the 18? I know it works on the smaller ones, but I'm concerned that maybe it won't supply enough volume, and I might be better off trying to locate a bypass cover and using a standard pump. Obviously, this would be very easy to do, but I've got a pile of vacuum pumps from the plastic circular briggs replacements to the Mikuni retangular one. What do you think?

 

[nwcove]

Re: Pressure tank to single line, 1957 18hp Evinrude

you need to post some pics of what you are referring to? those pumps dont work from vacuum alone, they need a pressure pulse and a vacuum pulse to operate the diaphram. as far as the inline filter, connect it as close to the engine as possible, in the single line , before the "clip on" connector. ......where you dissconnect the tank from the motor after you're done boating.
you should have no problem with a single line mikuni, if its in good working order.

 

[cr9c1]

Re: Pressure tank to single line, 1957 18hp Evinrude

Thanks. That answers it. Yes, I knew they need a vacuum and pressure pulse to work correctly. The way its hooked up now (using the previous pressure port on the intake, with the check valves removed and one port blocked) it should do the trick nicely. I'll hook an inline filter up. You're saying as close to the fuel connector as I can get it? Shouldn't be a problem.

I found a dead spark plug wire tonight, so I'm going to replace them both. The replacement have to be solid core, any other requirements?

 

[nwcove]

Re: Pressure tank to single line, 1957 18hp Evinrude

all you need is the basics, compression, GOOD spark, and good fuel/air. if the motor hasnt been run for awhile, the top secret files (you probably already looked there) are majorly helpfull! if you have troubles, and are sure that the conversion was done right, look for vacuum leaks on the tank end of things.

 

[cr9c1]

Re: Pressure tank to single line, 1957 18hp Evinrude

Thanks for the tips. I should have it fired up in a day or two. I gotta grab an inline filter and some new plug wires.

 

[nwcove]

Re: Pressure tank to single line, 1957 18hp Evinrude

best of luck, and dont get discouraged, most problems with the oldies are simple fixes that get overlooked and overthought!

 

[cr9c1]

Re: Pressure tank to single line, 1957 18hp Evinrude

Thanks. I got a lot of experience on the older pre-CDI outboards. This is my oldest I have worked on though, so its been a learning curve converting it to single line tank vs pressure tank. All the other stuff, plug wires, coils, points, condensers, done it all. As well as rebuilding carbs.