1992 40HP Johnson

[gimli1977]

Hello
I have a 40 horse Johnson outboard on a Tracker boat. I had to completely rebuild the powerhead when I bought the boat due to what I think was a failure with the oil injection. Anyway, I got 95% done with about three years ago, lost interest, and there it sat in my garage until I decided to pick the project back up now.

My question is concerning the fuel pump. I'm really leaning heavily toward just mixing my gas and doing away with oil injection. Anyone think I shouldn't do that with this motor? If it is a good idea, can I use the current fuel pump, or do I have to get a different one? My Johnson manual recommends 50:1 ratio for idling for testing purposes, but would I want to go a little richer if I'm going to run it with mix gas all the time? Also, I have never fired the motor up after rebuilding it. Anything important I should do before I try it?

Thanks a lot!

 

[tashasdaddy]

Re: 1992 40HP Johnson

i have the same motor, only 1993, i premix my fuel, i removed the mixing fuel pump, but to save $$ there is nothing wrong with using the existing, until it craps out. just cut the oil line about 1 inch from the motor, and plug the line, remove the wiring harness to the oil thank, and unplug the wiring connector to the fuel pump. mix you gas, remove a fuel line at the carbs, pump the fuel line primer bulb, until you get premixed gas there. connect line and go fishing.

replace the impeller before taking it out. the existing one will fail on you.

 

[gimli1977]

Re: 1992 40HP Johnson

Thank you very much for the info...that helps me a lot. I do have a new impeller to go in it, so I will replace it. Supposing I was going to replace the fuel pump, would you have a recommendation on a particular one. Also, should I be going richer than 50:1??

Thanks again!

 

[Silvertip]

Re: 1992 40HP Johnson

Since you aren't sure whether or not it was the oil injection system that caused the failure, it may not help to pre-mix if the problem was caused by gummed up carbs that cause lean mixtures. After rebuilding an engine it is always a good idea to totally rebuild the carburetors as well. This avoids the possibility of another failure. The engine is designed to run on 50:1 so run it 50:1. No sense smoking up the lake any more than necessary.

 

[tashasdaddy]

Re: 1992 40HP Johnson

50:1 is all it needs, i use this one, and plug the pulse line to the old pump. http://www.iboats.com/Sierra_18_735...z.36857--**********.853287910--view_id.174141

there should be a 1/4 inch plug on the port side of the block with small bolt hole on each side.

 

[gimli1977]

Re: 1992 40HP Johnson

Thanks again for the info both of you! I should have mentioned that I did rebuild the carbs before I tore into the powerhead. Originally when I bought the boat, the previous owner told me they needed to be rebuilt, as the motor had a rough idle. To make a long story short, I rebuilt the carbs, the boat still ran pitiful, so I checked the compression (something I should have done first, but you live and learn) and I had 80 psi in the top and 15 in the bottom. When I pulled the cylinder head off, I could literally wiggle the bottom piston back and forth in the block it was so chewed. They don't make a sleeve for this block, so my fathers machine shop made one for me, and the machinist did a perfect job on it. So it's been bored 030 and put back together. I am making the assumption that it was the oil injection, but hopefully I've taken care of it either way.

Thanks a lot!!