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Mercury 40 HP 2 Stroke 4 Cyl. Oil is everywhere!

E

eclipseguy

Member
I rebuilt this engine about a year ago. The problem I have has been an issue before the rebuild.
So you can run the engine (runs good) Shut it down for a few hours and is had to start once it starts smoke everywhere and a good oil slick on the water.
A few weeks ago I tried to stat (sitting a month trimmed down) it and would not turn over. I pulled the plugs and rolled it over now the side of my house is covered in oil!
Seems if the crank case is filling up with oil while sitting.
Its almost like the oil is being siphoning in the crank via the carbs... I checked the check valve at the fuel/oil line and seems good and the check valve on the block from the crank bearing that feeds oil to the top.
What am I missing?
Thanks
 
what year. maybe bypass oil injection and go to premix,put a shut off valve on the oil line and turn off when not being used. if this motor has an oil line going to the crank case, crank case seal possibly bad. Same problem with older Sea do skis. bad crank seal allows oil to enter by gravity and ends up with your symptoms
 
I have one of those engines in stock. I went out to the shop and took a look. Tight fit, but you should be able to remove the oil pump without having to remove the powerhead. What is your engine serial number? $375 for a new pump
 
faztbullet said:
Check the oil pump as the seal likes to back out.
Click to expand...
That really makes sense.
Looking at the service man I see two orings.
One seems to seal the pump to the block and the other looks like it seal the bearing to the pump. I will replace them anyway since they are from 1997!
I am just trying to figure out what seal is sealing what.
Thank you
 
fitz73222 said:
I have one of those engines in stock. I went out to the shop and took a look. Tight fit, but you should be able to remove the oil pump without having to remove the powerhead. What is your engine serial number? $375 for a new pump
Click to expand...
I would rather try to fix it than replace but, I will keep in mind .
Thank you
 
Where the shaft exits pump there is a oil seal
1740780440313.png
 
I pulled the pump off with the line connected. About 24 hrs later oil started leaking out between the shaft and the seal.
This problem has been bothering for so many years!
I ordered a new pump since the org one is about 30 years old.
Looks like the seal should be replaceable...
Thank you guys for the help! I was really thinking about buying a new engine.
 
Take care of that engine. It was one of the best engines Mercury ever produced; 4 cylinder 44 cu in, far better than any 4 stroke they produce today.
 
Just for fun question. The reason I did a rebuild was the reed block on 3 and 4 broke the dowel pin and moved so the rod hit the reed "stops".
I bought a new reed block and the dowel hole in the engine block had a nice grove from the reed block moving around.
Sometimes that engine did have a hard time turning over like a weak battery.
I wounder if the stress from the oil in #4 was working that reed block too much until it let go?
Doesn't make sense because I would think it would hurt the rod/bearings first.
 
I know the plastic dowel pins have been known to break in those reed blocks from incorrect assembly practice. I would have thought the connecting rod rubbing on the reed stop would have made a heck of a racket, lucky the engine didn't swallow any pieces from that collision of parts. I doubt excess oil had anything to do with the pin failure. My $.02
 
This engine only had metal dowel pins. With no bolts from the intake to hold everything together even the blocks are drilled and taped for a bolt.

I did finally took it out on the water after a starter issue.
No more hard starts that looks like the boat turned into a freight train!!
Power is better but, I still need to undo the adjustments I made while the engine way to full of oil!
 
eclipseguy said:
This engine only had metal dowel pins. With no bolts from the intake to hold everything together even the blocks are drilled and taped for a bolt.

I did finally took it out on the water after a starter issue.
No more hard starts that looks like the boat turned into a freight train!!
Power is better but, I still need to undo the adjustments I made while the engine way to full of oil!
Click to expand...
I'm talking about the reed block halves, not the pin that keeps the reed valve centered in the block.
 
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