# 2018 yamaha needs lower unit seal(s)



## sjrobin (Jul 13, 2015)

mwolaver said:


> Just wanted to share a bit of operating experience on my 2018 yamaha F40la, tiller. At just over 200 hours I completed my full maintenance today including: water pump full kit, thermostat, engine oil, lower unit lube, greasing, fuel filter replacement, anode inspection, spark plug inspection.
> 
> Unfortunately, the lower unit fluid was butterscotch, so I will be needing a pressure test and seal(s) now. This is a relatively young engine with a factory water pump and seals. I'm very careful with it. It has never had a temperature alarm incident of any kind. Pump was in very good condition when I replaced it. The lower unit lube was replaced at 10 hours and 100 hours, prior to today.
> 
> ...


Run it until a little water drains on the 100 hr lubricant change. Or check again and change at 50 hr. Modern lubricants still do the job with an emulsion. Very common.


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## mwolaver (Feb 6, 2014)

Thanks for that. Yes, I agree, there should be no lasting damage. Doing a family vacation in June, so want it solved within the next month. May run it for an hour, then drain and look again.


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## Frank Ucci (Jan 20, 2019)

Make sure the little gasket is in place on the drain and filler screws on the lower unit. I inadvertently dropped one after a fluid change and ended up with some water in the lower unit. Also, I have had fishing line wrap around my prop shaft and displace the shaft seal enough to allow water into the lower unit but without cutting the seal. Once I removed the line everything was back to normal.


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## mwolaver (Feb 6, 2014)

Thanks, Frank. Yes, I know those fill and drain screw gaskets. Mine were in place. Recently replaced my prop and inspected and lubed the shaft...no issues. Appreciate your ideas.

Mark


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## ek02 (May 8, 2012)

The upper driveshaft seals are a common source of water in the lower unit, the plastic seal housing usually needs to be replaced when doing the seals. Yamaha now sells black filler and drain plug gaskets. The red gaskets are not recommended by dealers. The prop shaft seals are more difficult to replace. You need the factory puller to get the housing off. They are usually frozen and may need heat to get it to come out. Corrosion builds at the very rear of the lower unit and that’s where the heat is needed. If you can get the housing out the seals are easy to replace. I would try the upper seals first.


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## mwolaver (Feb 6, 2014)

Great info, EK. Yes, the double lip seal under the water pump has always been the issue on the other boats. Ticks me off that I just had the LU off to rebuild the pump. 😢 Still think 200 hours is rediculously short service.


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## ek02 (May 8, 2012)

The shop manual shows the lips on all seals go toward the water. Evinrude seals used to be installed one toward water and one toward the oil. I know how you feel after just doing the pump. Now you will need more gaskets for the pump. 200 hrs is not very many to have water in the lu oil. I put all the seals in our F40 and it still gets a trace of water in the oil. Also, there is a rubber encased bushing in a plastic or Teflon insert that the driveshaft rides in. It’s held in with a snap ring in the mid section. It gets so much corrosion around it if used in salt water that I had to cut it out with a hack saw blade. I keep one in stock and replace it when I do the water pump. The thermostat gets plugged too if you run in shallow water and kick up mud and grass. I clean the housing with a plumbers wire brush and flush it out with the flush port. My 90 2 stroke never gets water in the lu oil and the thermostat always looks like new. The F40 has some quirks about it. Hope you get yours fixed.


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## mwolaver (Feb 6, 2014)

Getting it pressure tested tomorrow...then the seal replaced. I did the thermostat...amazing how cruddy it was behind the old one. That area is a VERY LOW flow passage, except when the thermostat opens. So when we flush with fresh water at the house, hardly any flushing takes place right there. It's good advice to replace the thermostat each time you do the pump.


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## mwolaver (Feb 6, 2014)

I just dropped the lower unit again. I saw that grommet and snap ring. Mine looked pretty good. I sprayed it with T-9 and moved the snap ring around some to get the T-9 behind it some. I'll leave it alone until next time. Thanks for the head up.


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## mwolaver (Feb 6, 2014)

Pressure test confirms upper (driveshaft) seals. Plastic carrier will get replaced due to damage upon disassembly.


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