Johnson Evinrude 9.9/15 lower unit interchange

[fleetwin]

Well, I guess I better save any old housings I have. I could surely see me adding the oring on a unit I was not familiar with and getting the driveshaft stuck up there or ripping out the seal…

[Mumbles]

If you try installing an early shaft with an O ring on it thru the later double seals, you’ll know right away something isn’t right as the O ring doesn’t want to fit thru the small lower seal very easily. I’ve been caught on this before and it would take a big grunt to get the O ring thru the seal! If I remember correctly, the lip on the lower seal faces out, towards the water pump, to keep water and exhaust out while the lip on the larger upper seal faces in to keep crankcase pressure/vacuum where it should be.

[PugetSoundBoater]

All very good information! I bring up topics and questions every now and then that seem to get a lot of interest and responses and seem to need discussing.I could have spent several hours on ME ,looking at parts diagrams and parts #’s for all these years trying to sort it all out.
Thanks so much to all of you, Jim PSB

"Some people want to know how a watch works, others just want to know what time it is"
Robbie Robertson

[PugetSoundBoater]

quote Mumbles:

If you try installing an early shaft with an O ring on it thru the later double seals, you’ll know right away something isn’t right as the O ring doesn’t want to fit thru the small lower seal very easily. I’ve been caught on this before and it would take a big grunt to get the O ring thru the seal! If I remember correctly, the lip on the lower seal faces out, towards the water pump, to keep water and exhaust out while the lip on the larger upper seal faces in to keep crankcase pressure/vacuum where it should be.

If that seals lower lip faced down, wouldn’t it get smashed and messed up by trying to fit the end of the driveshaft through the seal when installing the driveshaft while installing the LU. I had assumed that seal lip would face up. I do see and agree with Mumbles reasoning for the seal to face down keeping the water and exhaust out. There is a bevel on the top of the driveshaft, must be enough to let the shaft enter through the seal. Wish i had taken a look at the seals when i had the powerhead off my ’89 9.9 and made a note of the seals orientation.
Good info here! 😀

"Some people want to know how a watch works, others just want to know what time it is"
Robbie Robertson

[PugetSoundBoater]

Here is a screen grab of the crankshaft head for a 1976 9.9 of the M E site.
Shows the top one which i would assume is the original 0385971 (1 seal)and the lower one as the
2 seal unit (same as on a ’89 9.9) I think they have their wires crossed and have the parts listed wrong as it says the 0394327 is obsolete, they have 1 in stock ,they have 6 of the 0385971 in stock at a 1/3 the price. if you look at their site for the 1976 9.9 and click on the "more info" on the part, you will see what i am talking about. Somethings weird here or it is too late at night to be doing "research"

"Some people want to know how a watch works, others just want to know what time it is"
Robbie Robertson

[Mumbles]

quote PugetSoundBoater:

If that seals lower lip faced down, wouldn’t it get smashed and messed up by trying to fit the end of the driveshaft through the seal when installing the driveshaft while installing the LU. I had assumed that seal lip would face up.

Both seals are installed from the top of the carrier so the bottom part of the casting should act like a guide. The bottom seal might face up but it’s been a couple years since I worked on one. That’s why I said ‘If I remember correctly’. Now I gotta find one of those double seal units in my stash so I’ll be able to sleep tonight!

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