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View Full Version : Oil leak Mercury 125hp 2-stroke



Rolle85
07-23-2019, 03:34 PM
As many others I have an oil leak on my Mercury 125hp from 2002. It happens after I have been using it but I can not understand from where it comes.
Has someone actually managed to find the root cause for this?
br

fastjeff
07-23-2019, 07:02 PM
You can buy an oil additive that shows up brilliantly in ultra violent light. Finds the tiniest oil leak.

Jeff

Rolle85
07-24-2019, 02:51 AM
So noone has ever found the leak that so many suffers from?

Rolle85
07-24-2019, 08:39 AM
Is that so? :o

racerone
07-24-2019, 08:50 AM
The battery in my crystal ball is dead.-----I for one can not see where the oil is leaking on your motor.----Any pictures of this leak ?

bobbyc
07-24-2019, 10:18 AM
Leaks all the time??? Running only??? When tilted?

johnson110
07-24-2019, 11:17 AM
I had a leak in my 115 hp mercury 4 cylinder the leak was where the power head meets the lower unit, Bolts were all loose tighten them up leak gone!

Rolle85
07-24-2019, 11:34 AM
It only comes when tilting up after usage.
Can oil pore out through the carburetors?

fitz73222
07-25-2019, 01:33 PM
Its leaking from around the oil filler cap. They all did it. Take the cowling off, fill the oil tank about 3/4 full and mark a line on the tank where the oil is with a sharpie with the engine in normal running position. Next, tilt the engine up until the oil just reaches the filler neck on the oil tank below the cap o ring. Next take a piece of white masking tape and place it between the stern bracket where your steering cable enters the bracket and the bracket that actually swivels up and down as you tilt the engine. Cut the tape at the joint and this will become your visual reference as to how far you can tilt engine without it leaking. When the two pieces of tape line up when your tilting up that's where you stop. It was a stupid design that leaked almost from brand new. I have twin 115 's that did this from day one. Now when you go to fill your oil tank back up, only fill to your reference mark on the side of the tank and you wont have any more leaks.

Rolle85
07-25-2019, 03:36 PM
Its leaking from around the oil filler cap. They all did it. Take the cowling off, fill the oil tank about 3/4 full and mark a line on the tank where the oil is with a sharpie with the engine in normal running position. Next, tilt the engine up until the oil just reaches the filler neck on the oil tank below the cap o ring. Next take a piece of white masking tape and place it between the stern bracket where your steering cable enters the bracket and the bracket that actually swivels up and down as you tilt the engine. Cut the tape at the joint and this will become your visual reference as to how far you can tilt engine without it leaking. When the two pieces of tape line up when your tilting up that's where you stop. It was a stupid design that leaked almost from brand new. I have twin 115 's that did this from day one. Now when you go to fill your oil tank back up, only fill to your reference mark on the side of the tank and you wont have any more leaks.

I was just out with the boat, I see a oil film around the lower unit when I turn off the motor even before I tilt it up..😥

fitz73222
07-25-2019, 04:00 PM
Take the cowling off the engine and see if the insulating foam in the front of the cowling is soaked with oil. The oil could be leaking out of the lower pan and dripping into the water. Start looking for where it is coming from!

Rolle85
07-25-2019, 04:24 PM
Take the cowling off the engine and see if the insulating foam in the front of the cowling is soaked with oil. The oil could be leaking out of the lower pan and dripping into the water. Start looking for where it is coming from!
Ok will check.

Rolle85
07-27-2019, 05:13 PM
Ok will check.
the cowling has no oil, but I could today also see that it had leaked even when standing still for a day..At this time I had only tilted it up just slightly..
any clue?

fitz73222
07-27-2019, 08:20 PM
Ok,
So it sounds like the engine is leaking oil without it being tilted up. Do you see oil leaking out of the gearcase? Does the engine really smoke a lot when you first start it up? It's a clue. Typically this can be caused by a faulty oil check valve in the oil injection path. It's a small brass 2 psi check valve that prevents the oil from the oil tank gravity back feed into the engine, into the carbs and out into the engine block where it starts to dump oil onto the floor. Is this what you are seeing?

flyingscott
07-28-2019, 12:55 AM
Take the airbox off and look inside of that.

Rolle85
07-28-2019, 03:43 PM
Take the airbox off and look inside of that.
Yes theres oil laying in the carburetor intake visible behind the air filter. Is there a manual or film showing how to change the valve?

fitz73222
07-29-2019, 09:12 AM
http://www.marineengine.com/parts/mercury-outboard-parts/125-4-cyl/0g760300-thru-0t979999-usa/fuel-pump

item 26

Rolle85
07-29-2019, 10:47 AM
http://www.marineengine.com/parts/mercury-outboard-parts/125-4-cyl/0g760300-thru-0t979999-usa/fuel-pump

item 26

Great thanks! Will change once the boat is on land again!
thx!
One question, this is for the fuel pump, was it not oil pump issue?

fitz73222
07-29-2019, 11:05 AM
This is the check valve between the fuel pump and the oil pump. I have replaced this valve on every oil injected Merc I've had for the same issue you are having. One thing you will need to do after you replace that check valve is to remove your spark plugs and place a piece of cardboard behind the spark plug holes and turn the engine over to get excess oil that had accumulated in the bottom cylinders. Otherwise you are going to have a smoking mess when you fire it up for the first time because your engine is loaded with oil right now.

Rolle85
07-29-2019, 11:46 AM
This is the check valve between the fuel pump and the oil pump. I have replaced this valve on every oil injected Merc I've had for the same issue you are having. One thing you will need to do after you replace that check valve is to remove your spark plugs and place a piece of cardboard behind the spark plug holes and turn the engine over to get excess oil that had accumulated in the bottom cylinders. Otherwise you are going to have a smoking mess when you fire it up for the first time because your engine is loaded with oil right now.

Do you mean that by changing the valve a lot of oil will poor into the cylinders while I make the change?
So remove all sparkplugs and turn the startkey?

fitz73222
07-29-2019, 12:49 PM
Usually there is an excessive amount of oil in the engine when the valve goes bad and they smoke a lot when you start them. Yes, remove the spark plugs. Make sure you ground the coil leads; put the plugs back on the plug wire and make sure they touch the block to keep from harming the ignition system. Turn the key to start and turn the engine over for 5 seconds to make sure there is no residual oil in the engine. Also, since you are disturbing the oil system on the engine you may introduce air into it. When you start the engine for the first time after you replace the valve, make sure you start it on a remote tank with a 50-1 mixture of oil and gas so the engine is being lubricated while any potential air is bled through the oil injection system, 10 minutes should do it, then switch back to your normal fuel supply.

Rolle85
07-29-2019, 01:53 PM
But can I just start up without removing the plugs?
Do you by chance have a picture where to locate the check valve? ��

fitz73222
07-29-2019, 02:12 PM
Yes, you can start without removing the plugs. Use the parts diagram as reference for the location. I don't have a picture of it. It's inside the engine right behind where the fuel line enters the engine underneath the air silencer box. It's made of brass, you cant miss it.

Rolle85
07-29-2019, 02:40 PM
Yes, you can start without removing the plugs. Use the parts diagram as reference for the location. I don't have a picture of it. It's inside the engine right behind where the fuel line enters the engine underneath the air silencer box. It's made of brass, you cant miss it.

great, I will take pictures during autumn and show =)

Rolle85
08-01-2019, 02:20 AM
great, I will take pictures during autumn and show =)
Hi again, I was talking to a local outboard repair shop and he believed it was the reed valves who are the problem. This since oil shows itself on the water surface after usuage and before tilting the motor up. What you think?

fitz73222
08-01-2019, 07:29 AM
Reed valves have nothing to do with oil leakage. The engine has check valves that control puddled oil in the bottom of the crankcase at feed it to the upper main bearing in the engine. Since you are consulting with a repair shop I suggest you let them decide on what to do next and let them repair the engine.

Rolle85
08-01-2019, 12:45 PM
Reed valves have nothing to do with oil leakage. The engine has check valves that control puddled oil in the bottom of the crankcase at feed it to the upper main bearing in the engine. Since you are consulting with a repair shop I suggest you let them decide on what to do next and let them repair the engine.
Ok I will change the valve during autumn, thx

Rolle85
08-01-2019, 01:27 PM
Ok I will change the valve during autumn, thx
parts ordered on ebay from the US

Rolle85
08-05-2019, 02:59 PM
Hi, can you locate the area on this picture?
21324

fitz73222
08-05-2019, 03:18 PM
Yes, you can see it in the photo, Look down next to bottom air intake for the airbox. You see the brass fitting? its plugged into a molded fuel line and then into your fuel pump. It's very easy to change.

Rolle85
08-05-2019, 03:26 PM
Marked in red? Shall it be pulled out?
21325

Jhanratt
08-05-2019, 03:53 PM
TIMES TWO ON THIS POST!!!!

I own a 125 and They leak from the breather at the top of the tank when tilted full up!

Its leaking from around the oil filler cap. They all did it. Take the cowling off, fill the oil tank about 3/4 full and mark a line on the tank where the oil is with a sharpie with the engine in normal running position. Next, tilt the engine up until the oil just reaches the filler neck on the oil tank below the cap o ring. Next take a piece of white masking tape and place it between the stern bracket where your steering cable enters the bracket and the bracket that actually swivels up and down as you tilt the engine. Cut the tape at the joint and this will become your visual reference as to how far you can tilt engine without it leaking. When the two pieces of tape line up when your tilting up that's where you stop. It was a stupid design that leaked almost from brand new. I have twin 115 's that did this from day one. Now when you go to fill your oil tank back up, only fill to your reference mark on the side of the tank and you wont have any more leaks.[/QUOTE]

Rolle85
08-05-2019, 04:10 PM
TIMES TWO ON THIS POST!!!!

I own a 125 and They leak from the breather at the top of the tank when tilted full up!

Its leaking from around the oil filler cap. They all did it. Take the cowling off, fill the oil tank about 3/4 full and mark a line on the tank where the oil is with a sharpie with the engine in normal running position. Next, tilt the engine up until the oil just reaches the filler neck on the oil tank below the cap o ring. Next take a piece of white masking tape and place it between the stern bracket where your steering cable enters the bracket and the bracket that actually swivels up and down as you tilt the engine. Cut the tape at the joint and this will become your visual reference as to how far you can tilt engine without it leaking. When the two pieces of tape line up when your tilting up that's where you stop. It was a stupid design that leaked almost from brand new. I have twin 115 's that did this from day one. Now when you go to fill your oil tank back up, only fill to your reference mark on the side of the tank and you wont have any more leaks.[/QUOTE]
Mine leaks without tilting it up after being out driving. I have no traces of oil at the top of the oil tank.

Jhanratt
08-05-2019, 07:05 PM
I wish you the best of luck with it. My 150 HP mercury leaked constantly and everything under the cowl was oil covered until I started filling my oil tank half full. That was the end of my oil issues.

Rolle85
08-06-2019, 02:09 AM
I wish you the best of luck with it. My 150 HP mercury leaked constantly and everything under the cowl was oil covered until I started filling my oil tank half full. That was the end of my oil issues.
But theres no oil as you see on the picture all over the engine like you describe?

Jhanratt
08-06-2019, 12:10 PM
My oil leak was from the top of the oil tank at the breather. It would leak slowly while tilted up. The oil would cling to everything from the wiring harnesses to the engine to the insulation on the inside of the cowl and the cowl gasket. Then when I ran the engine it would get warm the oil would get thin and start running out everywhere. Mostly ending up in my motor well. Once I figured out not to fill the tank past about half my problem stopped.

Good luck with it!

Rolle85
08-06-2019, 01:38 PM
Marked in red? Shall it be pulled out?
21325
Can anyone confirm that it is the part marked in red on picture?

Rolle85
08-09-2019, 02:47 PM
Can anyone confirm that it is the part marked in red on picture?
Anyone?

Jhanratt
08-09-2019, 03:41 PM
http://www.marineengine.com/parts/mercury-outboard-parts/125-4-cyl/0t980000-thru-0t999999-usa/fuel-pump

use the link above or enter your own serial number in the engine diagram link above navigate to fuel pump.
Looks right to me based on the parts diagram and based on an inspection of my own 125 HP.

Good luck.

Rolle85
08-09-2019, 05:07 PM
http://www.marineengine.com/parts/mercury-outboard-parts/125-4-cyl/0t980000-thru-0t999999-usa/fuel-pump

use the link above or enter your own serial number in the engine diagram link above navigate to fuel pump.
Looks right to me based on the parts diagram and based on an inspection of my own 125 HP.

Good luck.
Did this solve your problem when you changed this valve?

Jhanratt
08-10-2019, 04:31 AM
http://www.marineengine.com/parts/mercury-outboard-parts/125-4-cyl/0t980000-thru-0t999999-usa/fuel-pump

use the link above or enter your own serial number in the engine diagram link above navigate to fuel pump.
Looks right to me based on the parts diagram and based on an inspection of my own 125 HP.

Good luck.

I did not have this problem nor have I ever changed this valve on my outboard.
My leak was from the air breather on the top of the tank or from the filler neck. My problem was solved by filling the tank no more than 1/2 - 3/4 full.
I was just trying to help. It looks like the valve discussed earlier the one is the same one in the image.

Jeff

Rolle85
08-10-2019, 12:03 PM
I did not have this problem nor have I ever changed this valve on my outboard.
My leak was from the air breather on the top of the tank or from the filler neck. My problem was solved by filling the tank no more than 1/2 - 3/4 full.
I was just trying to help. It looks like the valve discussed earlier the one is the same one in the image.

Jeff

can I put my fuel hose that goes from my fixed tank to a bottle of fuel mixed with oil after I have changed the valve? This to remove all airbubbles in the system before I plug it back to my fixed tank.
What mixing ratio shall it be?

Jhanratt
08-11-2019, 01:15 AM
I personally would try to make the swap quickly without losing oil from the line.
If I was not successful and lost oil or introduced bubbles then I would hook the motor to a portable tank of 50:1 and idle it until all the bubbles are bled from the line.
I have never worked on the oil injection system of these outboards but I have worked on the injector systems on my snowmobiles.
You can drive the oil pump on a skidoo by running the pump on a cordless drill to remove bubbles.
Not saying that would it work on this system because I don't know what drives it.

The above is just my opinion!

Be careful! 2 strokes require oil at all times.

Good luck.

fitz73222
08-12-2019, 02:24 PM
I gave you these instructions over a week ago as to what to do when you replace the valve...

Usually there is an excessive amount of oil in the engine when the valve goes bad and they smoke a lot when you start them. Yes, remove the spark plugs. Make sure you ground the coil leads; put the plugs back on the plug wire and make sure they touch the block to keep from harming the ignition system. Turn the key to start and turn the engine over for 5 seconds to make sure there is no residual oil in the engine. Also, since you are disturbing the oil system on the engine you may introduce air into it. When you start the engine for the first time after you replace the valve, make sure you start it on a remote tank with a 50-1 mixture of oil and gas so the engine is being lubricated while any potential air is bled through the oil injection system, 10 minutes should do it, then switch back to your normal fuel supply.