F80 lower unit leak behind prop

[yamahf80]

Have a slow leak behind the prop on the lower unit. Guessing the seal may be leaking. Do not have a pressure tester. Am wondering if anyone has had success with any of the "stop leak" products sealing older seals?

Something like Bardahl 3119 Gear Oil Additive Plus Stop, or Bar's Leaks 1040 Grey Rear Main Seal. Maybe one of the transmission or power steering stop leak products?

Have removed the prop and cleaned the shaft as much as possible without teardown. Looking for a short term emergency fix until it can be serviced properly.

Thxs.

[robert graham]

Look carefully for fishing line wrapped around prop shaft and under the seal causing seal damage/leakage/both....remove any fishing line. If seal is damaged you may refill lower unit with fresh oil and run it day to day for the short term, refilling as needed until seal repair can be done....freshwater this may be done, but saltwater is not so good even in small amounts. It's very doubtful any additives would repair a damaged seal....

[yamahf80]

Thxs for the reply Bob.

No fishing line or other cause for the leak is obvious. The seal appears to be all rubber. Is this something simple to change? Looks like it can be dug out with a sharp screwdriver.

Or does the prop shaft need to be removed? That would be above my skill level

[TownsendsFJR1300]

There's two prop shaft seals (likely your issue) and a much larger O-ring that
seals the main prop shaft "support" .

Technically, by the book, you should pull that center support out, use the Yamaha tool and knock the two shaft seals out. Again, there's another tool to push the new seals back in.

If your carefull, you can drill, then put a very small sheet metal screw into the seal. Once in tight, you should be able to pry it out. Repeat with the inner seal. **I would put a thin piece of sheet metal wrapped around the shaft just so you DO NOT DAMAGE IT..

The new seals should be re-installed with the SS spring (on both seals) facing outwards(see below pic). The circled part, #62 shows the direction of the seals. A correct size of PVC piping can carefully be used to get the seals in straight...

Parts #62 is what your after. Please pay attention to the direction of the seals..

[yamahf80]

Arggggg...I can clearly see the existing seal is in backwards. The spring is visible when the inner lip of the seal is raised, after the prop and thrust washer are removed. Hopefully that is the root cause and nothing more serious, as you mentioned.

Appreciate the diagram and the narrative! Not sure I want to tackle this but you give food for thought. Thxs.

[TownsendsFJR1300]

There's usually a stainless steel spring (very thin) that wraps around the inside of the seal and keep tension between the seal lip and the shaft. That spring goes away(breaks) with time.

Obviously the outside one appears ok.

Part #63, is the larger O-ring I was referrring to. If you can narrow down EXACTLY where the oil is coming from, it could be that o-ring. They do tend to flatten out with time. Of course, that'd (part #60) would have to come out..

Also, depending on who you talk to, that seal can go back in as yours is, I suspect to keep water from settling in there.


As a side note, I had the two UPPER drive shaft seals replaced (under the water pump plate) recently on my 06, F150.

Apparently its normal for the seals to go after time, even with flushing, etc. One of my seals was indeed bad, #2 was still fine but I had the both replaced. They did NOT pull the LU apart but picked out the seals.

[rodbolt17]

please DO NOT attempt to remove the seals without removing the housing.
it usually leads to a damaged shaft or a damaged housing.

when installing the seals ALL springs face OUT.
they face AWAY from the oil side.

most likely townsends drive shaft bearing carrier was removed for seal replacement.
I do 4 or 5 a week.
its a typical part of a pump job.

[TownsendsFJR1300]

Just as an FYI re seal removal W/O pulling the lower unit apart (as referred to in post #4):

Lower unit seal replacement pt 2 of 3 - lower seal removal - YouTube

[robert graham]

Just as an FYI re seal removal W/O pulling the lower unit apart (as referred to in post #4):

Lower unit seal replacement pt 2 of 3 - lower seal removal - YouTube

That's an interesting, almost backyard looking procedure....quite a trick...Any chance metal shavings from the drilling might find their way down into the bearings?.....

[yamahf80]

Watched the video a couple days ago before I posted here. "Messed Up But Useful" came to mind.

The diagram shows the springs facing outward...in the highlight circle. 99% sure I do not want to drop the lower unit. But you guys keep giving me knowledge which equals power...

Wonder if a self tapping screw would work using the backyard approach?

Am trying to get this boat cleaned up and sold. Would you buy a boat/motor with a know leak in this area?

How many hrs should a shop spend on making this repair?

Can't thank you all enough for the discussion

[TownsendsFJR1300]

That's an interesting, almost backyard looking procedure....quite a trick...Any chance metal shavings from the drilling might find their way down into the bearings?.....

Drilling the first seal, #2 is pretty much keeping any crap from getting deeper.

As for doing #2, should I attempt it (and it CAN INDEED, obviously be done), I would likely have a shop vac right in there as I'm drilling. That seal isn't terribly thick and the the bit is pulling debris upward.

Yes, its very "back yard mechainic" but for those talented enough, don't have the $ or a shop nearby, its an option.


I equate it to a very recent thread with water in the VST/lines.

In this thread: http://www.yamahaoutboardparts.com/f...g-th23655.html It was suggested spend 2 hours (that's if you know what your doing) pulling the VST apart, ALL the lines, flushing won't clean out the VST.

The owner ended up removing the fuel line to the fuel rail and pumping out a bunch of water. He did clean out the injectors as well. It was posted IT WOULD NOT WORK, it had to come apart. The guys engine now runs GREAT W/O pulling the VST pump, etc...

Is it the absolute, by the book, correct way, no... But it worked great, saved some work and the guys got a running boat again... I have NO problem keeping cash in my wallet vs dropping several hundred at the marina..

[TownsendsFJR1300]

Watched the video a couple days ago before I posted here. "Messed Up But Useful" came to mind.

The diagram shows the springs facing outward...in the highlight circle. 99% sure I do not want to drop the lower unit. But you guys keep giving me knowledge which equals power...

Wonder if a self tapping screw would work using the backyard approach?

Am trying to get this boat cleaned up and sold. Would you buy a boat/motor with a know leak in this area?

How many hrs should a shop spend on making this repair?

Can't thank you all enough for the discussion

Dropping the lower unit isn't that difficult. Two people make it easier, especially for re-assembly.. You saw the video, did it work, I saw that it did..

Would I buy a boat with this problem? If I knew about it and the price was adjusted accordingly.

If I was selling the boat, IMO, I would let the potential buyer know about it and adjust the $ accordingly. That's just the right thing to do...

I wouldn't want to get screwed buying the headache, I wouldn't pass it on to some poor slob, it simply just isn't right. Don't want or need the phone calls, potential small claims court, etc...

Re the cost, IDK. I suspect a couple hours shop charge, new oil, etc. Rodbolt should be able to give you an idea as he does them all the time. If its the prop seal, the main carrier would have to come out, (to do it by the book correctly). Wether the lower unit needs to be dropped, I suspect it would depend on the particular engine...

A phone call to your local Yamaha' service department should give you a good idea of the cost.

[99yam40]

If you do not want to drop the lower unit,What is the reason?

does this mean it has not been dropped in the last few years?
Or that it cannot be dropped, because of frozen bolts? Stuck drive shaft?
Seen a few of them and I would never buy a motor leaking seals or bad water pump with owner saying it is a cheap fix or discounting the price for a regular fix and then it ends up with a major expense with the other problems found taking it apart.

Fix it right and get top dollar for it or sell a broke motor.

As Rodbolt said, seals go with springs outward .
pay attention to the parts diagrams, do not take someones word for which way the seals go if the diagrams do not match what they say

[TownsendsFJR1300]

Just to add to the above.

In several Genuine Yamaha service manuals (for a certain Yamaha motorcycle (FZ6), there are some very incorrect torque #'s for various parts (oil drain plug-30' lbs SAME EXACT BOLT/aluminum block as the F150-20' lbs), etc.

More importantly, for doing a valve clearance check (shim set up, 4 valves per cylinder). It has you rotating the engine BACKWARDS, (CCW from right side of the engine) AGAINST the cam chain tensioner (CCT), a BIG NO NO.

Should the cam chain jump a tooth, being an interference designed engine,
600cc's, 95HP, it WILL BEND SOME VALVES at the very least if not destroy the engine if run.

Point being, if something doesn't seem right, it may not be and may be worth your while to question it. There are also many shortcuts NOT in the manual, ie it has you removing the throttle bodies,fuel tank, etc to get the thermostat out. It is tight BUT, the thermostat WILL come out without pulling any of the parts noted in the manual.

[rodbolt17]

can those seals be removed and installed without removeing the carrier.
yes.
can you destroy a prop shaft or housing attempting its, most definantly.

I can do a complete reseal on that case in about 3 hours.

self inflicted wounds can be painfully expensive.