# Did I overfill my lower unit?!?!



## Phil_the_fisch (Dec 22, 2013)

I was trying to save money by doing my own maintenance on my 2008 Yamaha 150 OB. Changed plugs, oil, oil and gas filters. Then went to lower unit. Took off both screws, changed the washers while the oil drained. Cleaned lower plug of metal shavings and then started to fill from the bottom with a Yamaha hand pump. Filled until oil came out top. Then I put on top plug and gave another pump. At that point oil started coming from the prop shaft area and from a small hole above the intake for the impeller. 


My question, did I break a seal or did the seal just release the pressure. The oil stopped coming out after I cleaned up. I hope I didn't just take all of my self maintenance savings and throw them away.


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## The Maintenance Shoppe (Nov 5, 2007)

you may have over pressurized the prop shaft seals. you need to take the lower unit to a shop and have them do a compression / vacuum test to reveal any seal problems.

if you skip this test, then you could blow the gearcase and cost yourself 1,500 dollars.


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## Phil_the_fisch (Dec 22, 2013)

How much does a shop charge to pressure test it. I'm going out on it sat/sun.


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## RMS (Dec 9, 2008)

If it were mine, and I own multiple yamaha outboards, I would go ahead and run the boat one day, as long as it's not a rig trip, and check a sample by pulling the lower plug at the end of the day. If the oil is milky then you have a seal problem, if not run it again and check it. If oil is still pure then you are good to go. 
I check my offshore boat lower units every 3 or 4 trips , my bass boat gets check once a year. I can put more miles on the offshore in two trips than the bass boat in a year.

A trip or two depending on miles per trip, with minor water instrusion isn't going to hurt the lower, but it needs to be remedied once discovered.

I've done the pressure test thing and it is an indicator, but it doesn't always equal reality.

My opinion is based on real experience over 40+ years of dealing with water in lower units.


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## Phil_the_fisch (Dec 22, 2013)

Thanks! I was planning a trip from boggy bayou to crab island. So maybe 20 or less miles. 

That's the idea a friend had given me as well. Will check when I start cleaning


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## floater1 (Oct 31, 2007)

Getting it resealed will be a whole lot cheaper then buying a new or having yours rebuilt if oil is coming out I will almost guarantee water can get in


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## RMS (Dec 9, 2008)

floater said:


> Getting it resealed will be a whole lot cheaper then buying a new or having yours rebuilt if oil is coming out I will almost guarantee water can get in


If you read his OP in detail he forced it to leak under pressure because he tried pump more oil in through the lower plug after he put the top plug in. He may or may not have permanently damaged a seal.

Any seal will leak if over pressurized, but isn't necessarily damaged.


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## Five Prongs Of Fury (Apr 15, 2008)

I also think you over pressurized both seals. Full is full, when it runs out the top hole, no extra is needed. As some others have said, make your trip and check it for water as soon as you get back.


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## floater1 (Oct 31, 2007)

I have resealed many what happens 95% of the time is that the inner seal spring comes off wich is the oil seal the out seal is more of a design to keep water out not oil in the inner seal is the main oil seal


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## Five Prongs Of Fury (Apr 15, 2008)

floater said:


> I have resealed many what happens 95% of the time is that the inner seal spring comes off wich is the oil seal the out seal is more of a design to keep water out not oil in the inner seal is the main oil seal


I can agree with you on this too. Pressure test is the only definitive way to test it. I would idle around in gear for a bit to see if any oil was coming out before the run across the bay.


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## sniperpeeps (Mar 5, 2011)

My buddy busted his seal doing the exact same thing on the same engine.


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## pdsw60 (Aug 12, 2010)

I wouldn't take the chance of burning it up. Take it to a shop before you put in the water. Better safe than sorry.


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## Phil_the_fisch (Dec 22, 2013)

sniperpeeps said:


> My buddy busted his seal doing the exact same thing on the same engine.
> 
> 
> Sent from my iPhone using Tapatalk


What did he do to fix it?


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## floater1 (Oct 31, 2007)

The only way to fix it is reseal the lower unit


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## sniperpeeps (Mar 5, 2011)

Phil_the_fisch said:


> What did he do to fix it?



He had it resealed


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## Snagged Line (Sep 30, 2007)

I did not watch the entire thing, but there is a lot of info on Youtube "How to Reseal Lower unit Yamaha Outboard"..............To give you an idea of what you are up against, and whether you want to give it an attempt or bring it to someone...


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## Sequoiha (Sep 28, 2007)

I'm gonna chime in now, there is no way a gear lube hand pump is gonna over pressurize the lower unit and make it leak, you have a bad seal and it needs to be fixed.


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## Sirhc (Sep 23, 2014)

Sequoiha said:


> I'm gonna chime in now, there is no way a gear lube hand pump is gonna over pressurize the lower unit and make it leak, you have a bad seal and it needs to be fixed.


Agreed.


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