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Loosing Oil from 40hp 2 Stroke Oil Resevoir

C

Captain Tinnie

New member
I have a 2005 2 cylinder 2 stroke 40hp Mercury outboard which is loosing oil from it's resevoir. I have unassembled and inspected the plastic tank and there are no leaks from the bottom outet or sight tube sites, the outlet hose to the oil pump is not leaking but have not yet pulled the oil pump off. The motor is in the down position and I have not noticed aoil oil leaking from the bottom cowling or parts of the leg, but the oil must be going somewhere. Are there some valves in the lines or oil pump? Parts for these older models are harder to find (in Australia) so what are you thoghts on removing the oil injection system all together and using a pre-mix. Thanks in advance for any help, Fred.
 
There are typically 2 causes other than an obvious leak include a stuck open oil checkvalve or an internal leak in the oil pump, I have repaired both conditions. A bad checkvalve can show up as excess oil back feeding oil into the fuel line causing very smoky starts. A faulty oil pump seal will start to drain the oil tank and the oil starts to fill into the engine block and eventually you see the oil leaking out of the engine on to the floor which makes quite a mess. A quick check for the oil pump issue is to remove the spark plugs, hold a piece of cardboard up behind the openings and turn the engine over with the key and see if it belches oil out of the bottom cylinder, there's your sign.
 
Thank your for your prompt reply. That sounds like a logical way to diagnose the cause of the problem. Will follow the steps and see what the result is. Your help is much appreciated, regards Fred
 
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