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Author Topic:   Yamaha Propeller Shaft Seal Orientation

pcrussell50 posted 10-08-2012 03:53 PM ET (US)
When changing the propeller shaft seals on a 1985 Yamaha 40 ELK, I removed the two that are in the bearing carrier and saw that they were NOT arranged back-to-back or smooth side against smooth side. Instead, I found both fore and aft seals with the spring side facing aft. I thought it was supposed to be the rearmost seal's spring side facing aft toward the propeller end and the frontmost seal with the spring side facing forward into the nose cone, as OMC and BRP do it.
Which way SHOULD they be: [I moved this sentence fragment from a separate posting were it was buried in a lengthy paragraph of unrelated text, to here--jimh] lips facing aft for BOTH seals, or forward seal with lips forward and aft seal with lips aft?
I wonder if some mechanic in the past did a hurry-up job and put them in wrong--should have been back to back--or does Yamaha use a different oil sealing logic where they are both supposed to face with the spring side outward in the direction of exhaust?
-Peter
outragesteve posted 10-08-2012 11:16 PM ET (US)
Peter: I just had the same thought when I resealed the unit on my F90. According to the Yamaha manual, the "lips" indeed face aft! I was going to take a look at a new engine at my local dealer, just have not had the time. Maybe another CW'er will respond. This is not the first time I've had the unit apart: I started questioning which way they go in. It just seems unconventional.
pcrussell50 posted 10-09-2012 02:19 AM ET (US)
Steve-O, got the manual safe and sound (and quickly)[ thanks.
According to the Yamaha contingent over on the "go-fast" forums, you do indeed arrange both propeller shaft seals with the lips facing aft. Also leave about a 5-mm gap between them, instead of pressing them in so the second one is touching the first. It seems like a "design-philosophy" thing. The lips in this type of seal are to keep out liquid from the side interfacing with the lip. OMC uses the same kind of seals back to back: one to keep the oil from getting out, the other to keep water from getting in. Yamaha apparently puts double-emphasis on keeping water out.
-Peter

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Author	Topic: Yamaha Propeller Shaft Seal Orientation
pcrussell50	posted 10-08-2012 03:53 PM ET (US) When changing the propeller shaft seals on a 1985 Yamaha 40 ELK, I removed the two that are in the bearing carrier and saw that they were NOT arranged back-to-back or smooth side against smooth side. Instead, I found both fore and aft seals with the spring side facing aft. I thought it was supposed to be the rearmost seal's spring side facing aft toward the propeller end and the frontmost seal with the spring side facing forward into the nose cone, as OMC and BRP do it. Which way SHOULD they be: [I moved this sentence fragment from a separate posting were it was buried in a lengthy paragraph of unrelated text, to here--jimh] lips facing aft for BOTH seals, or forward seal with lips forward and aft seal with lips aft? I wonder if some mechanic in the past did a hurry-up job and put them in wrong--should have been back to back--or does Yamaha use a different oil sealing logic where they are both supposed to face with the spring side outward in the direction of exhaust? -Peter
outragesteve	posted 10-08-2012 11:16 PM ET (US) Peter: I just had the same thought when I resealed the unit on my F90. According to the Yamaha manual, the "lips" indeed face aft! I was going to take a look at a new engine at my local dealer, just have not had the time. Maybe another CW'er will respond. This is not the first time I've had the unit apart: I started questioning which way they go in. It just seems unconventional.
pcrussell50	posted 10-09-2012 02:19 AM ET (US) Steve-O, got the manual safe and sound (and quickly)[ thanks. According to the Yamaha contingent over on the "go-fast" forums, you do indeed arrange both propeller shaft seals with the lips facing aft. Also leave about a 5-mm gap between them, instead of pressing them in so the second one is touching the first. It seems like a "design-philosophy" thing. The lips in this type of seal are to keep out liquid from the side interfacing with the lip. OMC uses the same kind of seals back to back: one to keep the oil from getting out, the other to keep water from getting in. Yamaha apparently puts double-emphasis on keeping water out. -Peter