Johnson 20hp drain/fill gaskets

[psteurer]

I have a 1989 Johnson 20hp. I just order two new drain plug screws for my lower unit since my old ones were getting marred. I also ordered a half dozen drain plug gaskets. When I got my order I was confused. The new drain plugs I got had nylon washers already on them. The half dozen drain plug gaskets were rubber o-rings. I would think the nylon washer could be used many times but the rubber o-rings should be replaced each time you change the lower unit oil. Anyone have a recommendation on which type of gasket is better to use? Which type is OEM?

 

[wilde1j]

Re: Johnson 20hp drain/fill gaskets

The type you use is determined by the drain plug, not what you want to use. Stick with the nylon ones. The O ring is used with a drain plug having an O ring recess on the seating surface of the plug.

 

[Daviet]

Re: Johnson 20hp drain/fill gaskets

When looking up parts for your engine I found
PN 307551 - screw
PN 333572 - o-ring
If you go back a couple of years this is what I found
PN 307551 - screw and washer
PN 311598 - washer
I beleave there is a misprint in the parts manual.
I have replaced the o-ring type screws with the plastic washer type with no problems. If you keep the new screws, return the o-rings and get the 311598 washers.
Have you got the o-ring type screws in your lower unit now?

 

[psteurer]

Re: Johnson 20hp drain/fill gaskets

Thanks. That makes a lot of sense. Should the nylon ones be changed every year when you change the lower unit oil? If so, I wonder if iboats sells them.

 

[Daviet]

Re: Johnson 20hp drain/fill gaskets

Yes, whenever you remove the screw you should use a new gasket, they compress and loose some of the ability to seal.

 

[psteurer]

Re: Johnson 20hp drain/fill gaskets

Thanks again. I remember when I bought the engine in October 2008, I had a hard time getting the drain plugs out. When I got them out with an impact screwdriver, I put on new gaskets. I can't recall what was there before. But I know I put on the Sierra (SIE-18-7145) which are suppose to be o-rings. I seem to recall though that the new ones were flat gaskets. I will check the drain screws when I take them off.