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Oil leak Mercury 125hp 2-stroke

R

Rolle85

Member
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
 
You can buy an oil additive that shows up brilliantly in ultra violent light. Finds the tiniest oil leak.

Jeff
 
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 ?
 
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!
 
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.
 
fitz73222 said:
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.
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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..😥
 
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,
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?
 
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.
 
fitz73222 said:
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.
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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?
 
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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.
 
But can I just start up without removing the plugs?
Do you by chance have a picture where to locate the check valve? ��
 
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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.
 
fitz73222 said:
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.
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great, I will take pictures during autumn and show =)
 
Rolle85 said:
great, I will take pictures during autumn and show =)
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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?
 
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.
 
fitz73222 said:
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.
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Ok I will change the valve during autumn, thx
 
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.
 
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