Conversion

[murraygw]

I saw somewhere that you can convert these older engines with pressure tanks to the newer plastic gas tanks. I have a 10hp 56 Johnson. Has anyone heard of this?

 

[F_R]

Re: Conversion

Of course. It stirs up a firestorm of comments every time it is mentioned. It can be done and if done correctly requires a different bypass cover plate to mount the pump. Get one off a newer junker motor. Other than that it is a simple hook it up and go deal.

 

[burroak]

Re: Conversion

I saw somewhere that you can convert these older engines with pressure tanks to the newer plastic gas tanks. I have a 10hp 56 Johnson. Has anyone heard of this?

I've done it with an 18 hp '58. Couple of ways to do it. 1. Get an single carb ATV, snowmobile, etc. pulse pump slap it on the motor somewhere. Connect the pump, using a new fuel line, to the crankcase nipple that was used for the pressure side of the two line system. You'll have to trade out the motor side fuel connector with a later model single line connector. It's located on the port side of the motor. Run a new fuel line from the connector to the fuel pump; out of the fuel pump to the carb.

2. Post a pic of the by pass cover plate side of you motor. That's were the most sanitary conversion can take place. I can not be certain without seeing the cover plates as to what is the best way to proceed.

 

[tashasdaddy]

Re: Conversion

i just completed it on a 1958 35 hp johnson. actually was very simple. i bought a pass cover that was suppose to be right, well it was exactly like the one on the engine. link below of pictures, i drill out the center hole, had the 2 hole tapped for mounting the fuel pump. ordered fuel pump and gaskets. give me a little few minutes to get things together and will and i'll give you the parts numbers i used with pics,

 

[tashasdaddy]

Re: Conversion

back with the pics. i'm not saying these parts will work on you motor, but the principle is the same. gasket for the by pass cover, 303615, gasket between by pass and fuel pump, 304784, fuel pump 438563, engine end connector 376154. you drill out the center hole and have the 2 side hole tap for 10/24 bolts, use 1 1/2" 10/24 bolts to mount the fuel pump, you will also have to have a larger diameter hose between the connector and the fuel pump. really was very easy, and i'm an advocate of keeping them original. here's a couple of pics. i can't get the second picture to upload directly of thru photobucket. send me a PM with you email request the fuel pump conversion, and i'll email direct. basicly on the lower half of the bypass cover the are what could be 3 holes in a line, you drill out the center hole, and tap the two outer.

 

[burroak]

Re: Conversion

I just remembered that I got a correct by pass cover plate and the fuel pump from a seller on Ebay, boattownmike. He has a lot of that old stuff. Try him, you may get a direct swap cover plate with the fuel pump. It will just be from a later model. I'm not familiar with the 10 hp but it seems like those designs weren't change that often. If you go with the by pass coverplate/fuel pump route, your friendly Napa dealer will have a brass 1/8" plug that will replace the pressure line nipple in the crankcase.

 

[tashasdaddy]

Re: Conversion

i just put a bolt in the hose with a hose clamp. forgot that part.

 

[F_R]

Re: Conversion

Burroak, if you got it to work that way, you are lucky. The impulse hose has to look at the crankcase where it receives alternating pressure and vacuum pulses to move the pump diaphragm back and forth. At the pressure fitting is only pulsating pressure, no vacuum pulses.

 

[tashasdaddy]

Re: Conversion

murray, FR is the one who told me how to do mine, and guided me thru it.

 

[burroak]

Re: Conversion

Burroak, if you got it to work that way, you are lucky. The impulse hose has to look at the crankcase where it receives alternating pressure and vacuum pulses to move the pump diaphragm back and forth. At the pressure fitting is only pulsating pressure, no vacuum pulses.

There is no luck in engineering. I may not have explained in a way that you have understood what I did. I simply put on to the motor the things that OMC did on later models. All of the 60s models and later motors get their impulse from the by pass cover plate and so does mine.

 

[F_R]

Re: Conversion

Sorry, I thought this was saying you connected to the air hose nipple which pressurizes the tank. Of course that's different than the bypass cover source.