# 2015 Mercury 20hp water in oil



## seapro17sv (Feb 3, 2015)

Overheated 15 miles from Chokoloskee and limped back to the island at 6-8 mph at full throttle. Didn't want to ruin someone's day asking for a tow and didn't see another boat anyway. Had a nice milk shake when I checked the oil of course, so assuming a possible blown head gasket. Am I correct, or are there any other possible issues, and did I do enough damage that it would be best to trash it and get another motor? The motor has 200 hours, flushed and garage kept since new, and oil changed approximately every 50 hours. Side note. When I noticed the overheating, I also saw what appeared to be about a 3" piece of an oily rubber gasket or seal hanging somewhere off the motor, can't recall where exactly. Could be something picked up off the water, but wondering if there is another seal somewhere that could allow water entry other than the head gasket? Either way, how big of a job is it for a mechanic to tear it down just to evaluate the problem and possibly do a repair. Any thoughts on how much the motor would be worth, selling it without doing a repair? Any advice or suggestions would be appreciated, thanks. Mike


----------



## Smackdaddy53 (Dec 31, 2012)

Overheating possibly caused the head gasket failure. Before scrapping it I’d replace the head gasket and run it again.


----------



## lemaymiami (Feb 9, 2007)

That "overheating" means you've got more than one problem to deal with (along with needing to have your lower unit re-habbed....). Before you do anything get that motor to a solid mechanic that works on that brand daily... and have it evaluated from top to bottom - and be willing to pay to find out exactly where you stand. You might not be in as much trouble as you believe - or it could be enough to total the motor, sell it for parts, and replace it...

At least that's exactly how I'd deal with it...


----------



## southerncannuck (Jun 27, 2016)

Water in the oil is almost always the result of a bad head gasket which is almost always the result of overheating. Unless something got so hot that it cracked or warped beyond repair it’s a fairly easy fix.
What caused the overheating is another thing.


----------



## Mike Haydon (Dec 19, 2019)

What ever you do get the old milkshake out and at the very least shoot wd40 in the cylinders and get some fresh oil in it. If not you will trash the bearings in a matter of no time.


----------



## Silent Drifter (Apr 29, 2021)

The guys already gave you solid advice 👍 you don't say anything about the pee stream ? I know if it was running hot you checked the pee stream was it strong ? Just wondering about the pump or blockage ,dont take long to over heat and blow gasket...other thought is thermostat malfunction? At 200 hrs id think the impeller would still be in good shape unless you run in sand a lot ....


----------



## Smackdaddy53 (Dec 31, 2012)

Silent Drifter said:


> The guys already gave you solid advice 👍 you don't say anything about the pee stream ? I know if it was running hot you checked the pee stream was it strong ? Just wondering about the pump or blockage ,dont take long to over heat and blow gasket...other thought is thermostat malfunction? At 200 hrs id think the impeller would still be in good shape unless you run in sand a lot ....


Could also be the opposite, if the head gasket was compromised it could have allowed water into the combustion chamber and or oil and caused the overheating due to loss of lubrication and the cylinder wall/walls could be badly scored. It’s all speculation without being able to inspect in person.


----------



## Capnredfish (Feb 1, 2012)

Smackdaddy is right. Just speculation and online entertainment for others at this point. But do follow some of the info and crack it open. Get the goop out in case it’s salvageable. Doing nothing but waiting almost guarantees it will be trashed.


----------



## flysalt060 (Aug 5, 2012)

Silent Drifter said:


> The guys already gave you solid advice 👍 you don't say anything about the pee stream ? I know if it was running hot you checked the pee stream was it strong ? Just wondering about the pump or blockage ,dont take long to over heat and blow gasket...other thought is thermostat malfunction? At 200 hrs id think the impeller would still be in good shape unless you run in sand a lot ....


Also what I was thinking. Either impeller bad or more likely you sucked up something. Take some 40 lb leader or weed wacker mono and clear the pee hole.


----------



## seapro17sv (Feb 3, 2015)

Capnredfish said:


> Smackdaddy is right. Just speculation and online entertainment for others at this point. But do follow some of the info and crack it open. Get the goop out in case it’s salvageable. Doing nothing but waiting almost guarantees it will be trashed.


Thanks for all of the great responses, I really appreciate everyone taking time to help out. A little more background info; Impellor is relatively new, I'd say less than 50 hours, and no previous problems pumping. When this happened we were pulling ourselves under and through some dense Mangroves in the Gopher Key Bay area. Had the motor idling so I could give it a little bump occasionally to help pull and push through the thick cover. Apparently the intake got clogged at some point, and I saw steaming hot water pissing out. Shut it down immediately, let it cool for quite a while, and when we were out in open water once again, fired it up and started back to the ramp. Ran about 5 miles when It lost power, so shut it down again briefly, but started it up again because it was pumping cool water and I wanted to make the 12-15 miles back to the ramp. Pissed like a racehorse the entire time, but full throttle only got 6-8 mph instead of my normal 25. Sounded like it was running on 1 cylinder. When I got back home a few days later, drained the oil, filled with new oil, and sprayed a bunch of CRC in the spark plug ports. Maybe too late on the preventative action of draining and replacing the oil. Anyway, that's where I'm at. I'll be telling a mechanic all of this sometime this week.


----------



## Mike Haydon (Dec 19, 2019)

Sounds like you clogged up the intakes and then it ran hot on you. You let it cool but didnt clear the obstruction so then you ran it and sounds like this is when you blew the head gasket. No top end after that because of loss of compression. If you drained it fast enough you will be fine. 

First I would change water pump and thermostat. Run it to make sure its pumping good again. Then your gonna have to drain the oil. Soak the parts down with fresh oil, marvel, wf-40, something. Now it's time to change the head gasket. Shouldn't be hard if you have a Haynes manual. Good luck bud. As everyone else said it's more if speculation but I'd be willing to bet this is your problem. And I'm not a gambling man.


----------



## Silent Drifter (Apr 29, 2021)

^^^^^^Well he sayed "Apparently the intake got clogged at some point," So 🤔 he needs to do as Smack suggested and change the gasket refill it with oil and see what hes got meaning how it runs and what the compression tells him 👍😎 if the rings didnt get messed up or the piston walls scored hes good to go i believe as they would be first to go then bearings....if all checks out then change oil again to remove anything left ....


----------



## 17376 (May 5, 2017)

Mike get all of that oil/ water out of there and fill it completely to the brim with marvel mystery oil.. pull plugs and fill them too.. I would say head gasket..


----------



## seapro17sv (Feb 3, 2015)

Northfl89 said:


> Mike get all of that oil/ water out of there and fill it completely to the brim with marvel mystery oil.. pull plugs and fill them too.. I would say head gasket..


Thanks to all you guys for your advice. Time for a mechanic to tear it down, don't think I want to attempt it myself. I'm sure it would come apart easy enough, putting everything back together again properly looks a bit intimidating.


----------



## southerncannuck (Jun 27, 2016)

Please share updates


----------

