# Seized Mercury 25 2 stroke



## Fernando Perez (May 7, 2021)

Jred said:


> Picked up a seized 2001 mercury 25 2 stroke, I love these engines and have had a few of them fixing any issue that ever comes around. I got a good deal on this one and my buddy and I are gonna see what we can do to bring it back to life.
> 
> With that being said, what’s the best way you’ve seen to help free the pistons? I’ve got a little 2 stroke oil soaking in the cflinders today but may add some Marvel Mystery Oil to it once it seeps through.
> 
> Worst case scenario I’ll have a parts motor as I have one in great running order already.


Just use any penetrating oil because it can seep into very small clearances. Watch some of thatboatguy’s videos on YouTube. He has freed up Several motors by hitting the crank gear with a soft punch like aluminum or brass and a hammer until it’s not seized and then he puts a ratchet and spins it until it’s loose. The only thing with that method if that you can break a rings or cause some other damage to the bores


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## Jred (Sep 22, 2013)

Fernando Perez said:


> Just use any penetrating oil because it can seep into very small clearances. Watch some of thatboatguy’s videos on YouTube. He has freed up Several motors by hitting the crank gear with a soft punch like aluminum or brass and a hammer until it’s not seized and then he puts a ratchet and spins it until it’s loose. The only thing with that method if that you can break a rings or cause some other damage to the bores


Yea that sounds like a last resort type of treatment haha. I’ll watch the videos thanks!


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## Smackdaddy53 (Dec 31, 2012)

Lay it horizontal and spray penetrating lubricant in the spark plug holes and let it sit then insert a hardwood dowel in each plug hole and tap the pistons a little then try to turn the flywheel or pull rope. Repeat until free.


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## Sdm111 (12 mo ago)

Atf is a good cheap penetrating lubricant


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## Jred (Sep 22, 2013)

Let the oil sit in cylinders overnight and added some Marvel Mystery oil today. Started working the fly wheel with a breaker bar and got it freed up. I took off the port side exhaust manifold and the pistons are un-damaged. next I’m gonna clean her up and add new gaskets/fuel lines and fuel pump lines


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## Sdm111 (12 mo ago)

Nice! Get it running and do a compression test to see how the cylinder walls and rings are. It's s a 2 stroke so a little low isn't that bad obviously to a point. You may be surprised


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## JC Designs (Apr 5, 2020)

Get a can of BRP engine tuner from an Evinrude dealer or online and use that as your “penetrating” lubricant. Trust me when I say… if that don’t free it up then it ain’t getting free’d up! Just spray it in the cylinder like mentioned above and walk away. You may have to spray them 3-4 times as the stuff foams up pretty good.


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## Jred (Sep 22, 2013)

on a side note, why does mercury make their bolt threads so short? It only took me about an hour and a half to get the rest of this [email protected]$tard out


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## JC Designs (Apr 5, 2020)

Jred said:


> on a side note, why does mercury make their bolt threads so short? It only took me about an hour and a half to get the rest of this [email protected]$tard out
> View attachment 195136


Looks like $150 bolt to me!😉


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## lemaymiami (Feb 9, 2007)

As a master mechanic explained to me years and years ago... Anyone can work on a two stroke when things are easy... When they're not you're going to be learning about heli-coils and other neat items - and most just aren't set up to drill out hardened frozen (or broken off) stainless steel bolts properly...

"Aren't boats fun?"


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## Jred (Sep 22, 2013)

lemaymiami said:


> As a master mechanic explained to me years and years ago... Anyone can work on a two stroke when things are easy... When they're not you're going to be learning about heli-coils and other neat items - and most just aren't set up to drill out hardened frozen (or broken off) stainless steel bolts properly...
> 
> "Aren't boats fun?"


Wasn’t looking for easy when I bought this motor as a project but thankfully it turned out to be Pretty easy. I love these motors due to the fact that they’re so simple and can be easily troubleshooted. the stainless bolt was _properly_ removed and original threads not damaged thankfully


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## Smackdaddy53 (Dec 31, 2012)

Jred said:


> on a side note, why does mercury make their bolt threads so short? It only took me about an hour and a half to get the rest of this [email protected]$tard out
> View attachment 195136


Probably not an OEM bolt.


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## Sdm111 (12 mo ago)

From building race dirtbike (3wheelers in my case) I've learned boy they can be finicky but when the planets align they run like a scalded dog. And run their best just before meltdown


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## Sdm111 (12 mo ago)

I dont know how it would do in the outboard world but I run Klotz super techniplate 2 stroke oil. My boats I've just ever used cheap 2 stroke but in the race engines I spend a little more on. And that smell mmmm.


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## bonitoman (May 20, 2021)

Sdm111 said:


> I dont know how it would do in the outboard world but I run Klotz super techniplate 2 stroke oil. My boats I've just ever used cheap 2 stroke but in the race engines I spend a little more on. And that smell mmmm.


I ran klotz 20 years ago when i could find it . It use to smell like soap dont know if it still does Great two stroke oil


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## Marshdweller08 (Aug 1, 2018)

Maxima Castor 927 is the sweetest smelling 2-stroke oil that i ran in all of my bikes. In fact i continue to hold onto my '97 KX250 just to get that aroma. Sold the rest of my newer 4-strokes.
I now use Maxima Marine Pro for my Merc 25 2-stroke which has been great. It doesn't have the aroma of the Castor 927 unfortunately.


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## sjrobin (Jul 13, 2015)

Jred said:


> on a side note, why does mercury make their bolt threads so short? It only took me about an hour and a half to get the rest of this [email protected]$tard out
> View attachment 195136


Because it is a Mercury


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## Hank (Jan 14, 2019)

I have to ask…

Are you sure its a good idea to break it loose and run it without looking inside? Doing that seems like a short trip to killing the motor when the remnants of the first seize create the final seize. I know sometimes a seized motor can just be run and it lasts but I would never count on that. And 2 strokes are too easy to take apart not to have a look.


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## Smackdaddy53 (Dec 31, 2012)

Hank said:


> I have to ask…
> 
> Are you sure its a good idea to break it loose and run it without looking inside? Doing that seems like a short trip to killing the motor when the remnants of the first seize create the final seize. I know sometimes a seized motor can just be run and it lasts but I would never count on that. And 2 strokes are too easy to take apart not to have a look.


Most that are seized are from sitting too long and the cylinder walls rust around the rings. Once they are freed up the rust will go into the crankcase and out the exhaust.


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## Jred (Sep 22, 2013)

Hank said:


> I have to ask…
> 
> Are you sure its a good idea to break it loose and run it without looking inside? Doing that seems like a short trip to killing the motor when the remnants of the first seize create the final seize. I know sometimes a seized motor can just be run and it lasts but I would never count on that. And 2 strokes are too easy to take apart not to have a look.


through the exhaust manifold I can see the sides and tops of pistons and the cylinder walls and nothing I’ve seen worries me what so ever so running it as is should be fine. If not then RIP


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## millerrep (Apr 14, 2014)

bonitoman said:


> I ran klotz 20 years ago when i could find it . It use to smell like soap dont know if it still does Great two stroke oil





bonitoman said:


> I ran klotz 20 years ago when i could find it . It use to smell like soap dont know if it still does Great two stroke oil


We ran Blendzall in the 70s in the flat trackers. Loved the smell!


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## Smackdaddy53 (Dec 31, 2012)

Jred said:


> through the exhaust manifold I can see the sides and tops of pistons and the cylinder walls and nothing I’ve seen worries me what so ever so running it as is should be fine. If not then RIP


How is this outboard running now? Just an update since it popped up.


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## Jred (Sep 22, 2013)

Smackdaddy53 said:


> How is this outboard running now? Just an update since it popped up.


Runs great, putting it on a spear legend kit I’m building


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## Smackdaddy53 (Dec 31, 2012)

Jred said:


> Runs great, putting it on a spear legend kit I’m building


Very nice!


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