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Lower unit oil screw stuck

Old 03-29-2021, 08:26 AM
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Default Lower unit oil screw stuck

Anyone have any tricks? Lower unit (top) oil screw won’t budge on 1993 Johnson 25hp
Old 03-29-2021, 08:36 AM
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PB Blaster and an impact screwdriver - Used this few times - no complaints
https://www.harborfreight.com/hand-t...ase-64812.html
Old 03-29-2021, 08:45 AM
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Yep, that impact driver and maybe some concentrated heat in the area of the screw. Once they are that tight it seems like PB blaster, Kroil, etc never seem to help...
Old 03-29-2021, 08:52 AM
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^^^^
Hand Impact Screwdriver & hammer with a good wide flat bit that fits screw is the ticket.
I've also had to heat the area with a hot air gun (till too hot to touch), then spray with good penetrating oil.
May have to repeat a few times. Patient persuasion is the key. Good luck.

Old 03-29-2021, 08:59 AM
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I have a screwdriver I ground the tip off to make it a bit wider so I really have to wedge it into the slot - that helps. Also, might be obvious but you've tried a wrench on the screwdriver shaft to give you leverage right? As mentioned above, tap the screwdriver with a hammer while you're turning.

Also, replace those screws when you service. Keep a sharp edge on the slot for next time.
Old 03-29-2021, 09:29 AM
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make sure it is a good beefy and properly sized screw driver so you dont round off that slot in the screw.
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Old 03-29-2021, 09:47 AM
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I bought the largest screwdriver that would fit and wrapped a towel around it and was able to loosen it.
Old 03-29-2021, 10:13 AM
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Old 03-29-2021, 10:39 AM
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Originally Posted by triumphrick View Post
Yep, that impact driver and maybe some concentrated heat in the area of the screw. Once they are that tight it seems like PB blaster, Kroil, etc never seem to help...
Maily because the the screw seals so the penetrating oil can't penetrate. Impact driver with a big bit.
Old 03-29-2021, 11:53 AM
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I have never used an impact driver to loosen that screw, but I did to free a ss screw into what I thought was a simple cover on my F115 Yamaha. It needed to come off to change the plugs.

One not very hard tap with the impact and the "cover" was cracked. It was part of the head and was about $500 to replace.
Old 03-29-2021, 11:11 PM
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Old 03-30-2021, 02:17 AM
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Originally Posted by Bob1957 View Post

NO! You need an impact screwdriver with a well-fitting blade like everyone is saying. You tap it with a hammer and it turns ever so slightly. It doesn't just have the turning action of an impact gun. You are driving it in while it turns slightly at the same time. 50/50 ATF/acetone, well mixed or PB blaster applied the day before. And like everyone says, replace the plugs every time or every few times so they stay sharp.
Old 03-30-2021, 03:18 AM
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Hello, I would also use the impact driver, usually if they´re that bad I get one of my huge mates to turn the screw whilst I tap the impact driver, the ATF/acetone penetrating fluid I've heard works well, brake fluid is nice and corrosive too. Patience is the key along with using the right size bit.
Old 03-30-2021, 04:33 AM
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When you are trying to work it, make sure you try and tighten it about 1/4 to 1/8 turn. Sometimes helps break the threads loose.
Old 03-30-2021, 08:15 AM
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Originally Posted by SeaPro48 View Post
NO! You need an impact screwdriver with a well-fitting blade like everyone is saying. You tap it with a hammer and it turns ever so slightly. It doesn't just have the turning action of an impact gun. You are driving it in while it turns slightly at the same time. 50/50 ATF/acetone, well mixed or PB blaster applied the day before. And like everyone says, replace the plugs every time or every few times so they stay sharp.
I probably change lower unit oil on 200 outboards every summer, ^ that's all I use. It "hammers" also, that's why they call it an impact.
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Old 03-30-2021, 11:50 AM
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Right tool helps
a standard screwdriver......is not the right tool


Old 03-31-2021, 06:36 AM
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Originally Posted by Bob1957 View Post
I probably change lower unit oil on 200 outboards every summer, ^ that's all I use. It "hammers" also, that's why they call it an impact.
He ( the OP) may not have quite the experience you do
Old 04-02-2021, 02:57 PM
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This is what I would use also. You need to make sure the flat blade fits snuggly in the slot and wide . I have ground the tip of one down so it’s tight in there.


Old 04-05-2021, 11:59 AM
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I use a dulled chisel just wide enough for the whole slot as a screwdriver.

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