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2004 Mercury 25 hp oil leak

T

TiEnv

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I have a 2004 mercury 25 hp 2 stroke outboard that appears to have an oil leak coming from somewhere under the powerhead. The motor starts and runs perfectly. I am wondering if this is a major issue and if it needs to be repaired how costly will it be? Does any have experience with this type of thing?
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Oil in the lower cowl can come from a number of sources.

If the oil appears/smells burnt it could be coming from a bad powerhead base gasket or an exhaust cover gasket.

If it's just kinda "goopy" oil residue it could be coming from a fuel leak (gas evaporates and leaves the oil behind), a disconnected bleed line, bad carb gasket, bad intake transfer cover gasket, bad powerhead base gasket, bad upper or lower crank seal, chipped or broken reed and probably a few other things I'm over looking.

You need to try and find the "source" - the result is that mess in the lower cowl.

Once you find "where" it's coming from then you can get a better idea of the cost to repair.

If you can do the work yourself it may be a simple as a 2 dollar gasket - if you need a shop, count on 100 bucks an hour plus parts - a couple hours if you need "them" to track down the issue...
 
The motor is on a boat I use for duck hunting. Early teal season is starting in two weeks. Is there any harm in running the motor through the season (2 weekends) then getting it looked it or does the issue need to be addressed ASAP?
 
If it seems to be running ok (not bogging, quitting on you etc) then it may not hurt anything in the short term.

As long as some of your gas/oil mix is getting into the crankcase/cylinders (which would be indicated by the motor running ok) then you shouldn't be in danger of killing anything quickly.

But, since I don't know if that mess in your cowl occurred after an hour of running, running all season (or two seasons), just started or has been "chronic" for a while, I can't give you a definitive answer.

I had a leaky upper crank seal that I took two years to get to. It left an oily film all over the motor (like it was sprayed with fogging oil or WD-40) - didn't hurt anything but the gas mileage and power of the motor.

It might be minor and all will be well, it could be serious and cause an issue - if it runs like crap I would address it sooner rather than later...
 
Thanks for the info. I will try to degrease the area and clean it all out then see how it re-accumulates and go from there.
 
The motor runs 26 mph on GPS with 500 pounds worth of guys in a 1648 weldbilt flat bottom boat which seems ok as far as power goes. I got the motor used and the oily residue was there when I got it home (didn't notice it when I have the motor a once over at the time of purchase). I will definitely clean it up and see what happens.
 
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