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Proactively change lower unit oil seals?

Old 10-15-2019, 04:51 AM
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Default Proactively change lower unit oil seals?

I am thinking of having the oil seals replaced on my lower units just as a preventative maintenance measure even though there is no evidence of leaking. My 2002 150HPDIs have the original oil seals however, with ~1000 hours on each engine I am worried that I may be living on borrowed time. Just curious if anyone proactively changes their lower unit oil seals even if there is no evidence of leaking. If so how many hours were on the engine when replaced?
Thanks!
Old 10-15-2019, 06:31 AM
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On a motor of that year, I don't think it's bad practice to have them changed in the offseason.
Old 10-15-2019, 06:34 AM
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I would say definitely a good plan. Did it this spring on '06 motors- it was overdue but they were new-ish to me. Besides, the parts need to be loosened and exercised from time to time to avoid corrosion freeze. If you don't do it when you can, you may not be able to later.
Old 10-15-2019, 06:51 AM
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I think it's definitely a good idea, and after my prop seal was compromised this season, I'll probably do the same going forward. It's not only the oil seals, but also the o-rings on the gear housing. My engine is at about 500 hours for reference, but it was compromised due to fishing line. But when I initially drained it, it looked like coffee with cream in it. Lots of water in there. I removed the gear housing to replace the seals, and I saw no noticeable damage inside. So I wouldn't say you're on borrowed time yet. Once it leaks, THEN you're on borrowed time. I would still pressure-test the lower unit every time you change the gear oil though. That might expose a leak that's just beginning to start.

A few extra dollars spent on oil seals isn't going to make you regret replacing them more often than needed.
Old 10-15-2019, 09:17 AM
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You're talking about the little gaskets on the two screws on the lower unit? They're like 99 cents, I change them every time I change the lower unit oil.
Old 10-15-2019, 09:23 AM
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Not sure which seals you mean but my Yamaha mechanic recommends replacing the driveshaft seals any time you do a water pump change. Cheap job since everything's already apart.
Old 10-15-2019, 09:50 AM
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All watercraft maintenance should be proactive. Waiting for parts to fail is expensive.
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Old 10-15-2019, 09:56 AM
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A solid NO.

Originally Posted by Febtober View Post
You're talking about the little gaskets on the two screws on the lower unit? They're like 99 cents, I change them every time I change the lower unit oil.
Old 10-15-2019, 11:30 AM
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If you want to know if your seals need replacing you should pressure test them. I posted on the thread listed below a while back. Changing the main shaft seal isn't that bad, but changing the prop shaft seals can be a bear depending on how corroded things are.

Lower Unit Pressure Test
Old 10-15-2019, 11:40 AM
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You've gotten varied answers, possibly due to there being several seals in a lower unit. I think all of them were addressed except the seal on the prop shaft which you were probably referencing. I've never run an engine 1000 hours, but if I did I think having the prop shaft seal changed out, bearings checked, and the overall lower unit serviced at the same time would be a good decision. However, I should state, if you are using the engine or engines in saltwater the lower unit will be a bear to take apart, thus your mechanic might discourage you.
Old 10-15-2019, 12:35 PM
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Originally Posted by dward View Post
If you want to know if your seals need replacing you should pressure test them. I posted on the thread listed below a while back. Changing the main shaft seal isn't that bad, but changing the prop shaft seals can be a bear depending on how corroded things are.

Lower Unit Pressure Test
Good point. The shaft bearing carriage has never been pulled. I can see how that could be challenging.
Old 10-15-2019, 12:38 PM
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Originally Posted by Bayfly View Post
You've gotten varied answers, possibly due to there being several seals in a lower unit. I think all of them were addressed except the seal on the prop shaft which you were probably referencing. I've never run an engine 1000 hours, but if I did I think having the prop shaft seal changed out, bearings checked, and the overall lower unit serviced at the same time would be a good decision. However, I should state, if you are using the engine or engines in saltwater the lower unit will be a bear to take apart, thus your mechanic might discourage you.
Yep..I agree. These engines have been in salt all their life. Good point on the disassembling challenges.
Old 10-16-2019, 05:24 AM
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If there is no evidence of water leave it alone.
Old 10-16-2019, 09:14 AM
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I do the top seals on mine at ~1000 hours but I will wait for evidence of a problem on the prop seal. The top seals are easy when you are doing the water pump and the "deluxe" water pump kit comes with them for my F70.
The main shaft seal under the water pump is the on that will completely fill the gear case with water when it fails.
Old 10-16-2019, 09:16 AM
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if it aint broke don't fix it.
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