Johnson lower unit question

[cajun/johnson 74]

I have a 74 johnson 70 hp and i need to know if my lower unit is supose to have pressure. I went to check the level of the fluid and i unscrewed the top screw and it had pressure on it. then i took it out on the lake and decided to change the fluid when i got home and it had the pressure back on it. Is this normal or is this something to worry about. thanks for all the help.

 

[F_R]

Re: Johnson lower unit question

Well not a requirement, but not too unusual either. I think some oils do that more than others. Lets just say my work shirts usually had little black dots all over them.

One thing about it, you know it's not leaking under pressure.

 

[Randybeall]

Re: Johnson lower unit question

Not very common, but if there is slight pressure you can be sure no water can get in. Did you drain the lower unit, and did the fluid come out milky? If it was getting water forced in by the pump it would have pressure and be milky. If it was clear to black your doing great. Fill it with fresh oil, replace the seals on the fill and drain plugs and go back to having fun.

 

[ezeke]

Re: Johnson lower unit question

When you fill the lower unit, fill from the bottom and stop when the fluid flows out of the vent. The extra room above that is to compensate for pressure when running and filling it can blow the seals.

 

[cajun/johnson 74]

Re: Johnson lower unit question

yes it was a little milky but it look like it was just old and bad. thanks for all the help guys its much appreciated.

 

[baiwan]

Re: Johnson lower unit question

Milky doesn't mean old and bad; it means there is water in it, and oil seals have to be changed.
That's what I'm trying to do now.

 

[tashasdaddy]

Re: Johnson lower unit question

first replace the seal washers on the fill and vent plugs, they are one time use only, also the #1 place for leaks, if not replaced. then if it is milky next time, time for a lower reseal.

 

[baiwan]

Re: Johnson lower unit question

That's exactly what I did last year, I replaced the o-ring on the gear shift lever as well and had to change oil ever day after boating.
I am changing the oil seals on the propeller shaft now and having "hard times" removing the gear casing, but I don't hurry, I"ll manage by May.
I hate water in the oil, it's bad for the wallet.