Water in Oil - 2003 Mercury 4 Stroke 75hp Outboard

[scjakester]

Hello all... I purchased a 2003 Pontoon boat last week (fully knowing there was a small amount of water mixed in the oil). I basically purchased the boat and the owner gave me the outboard. He said it was running fine over the fall, he parked it on his boat lift and went to start it a few weeks ago, when he checked the oil there was some water mixed in.

He said there were no whistles or alarms going off and that he checked the oil the last day he took it out (in December), and it was fine. He said all he could figure is that it had to have happened either on the way back to his boat lift that day or somehow while it was up on the boat lift itself?!?!?! I'm not going to attempt to start it, I'm taking it straight to a Certified Mercury Service Center and get a technician to go through it for me next week. I am kinda hoping it can be repaired (instead of repowered) but like I said, the motor was just a freebee either way, I only paid for the boat itself.

Anyone have any ideas on what could be wrong with it?

-Jake
South Carolina

 

[woody66912]

Re: Water in Oil - 2003 Mercury 4 Stroke 75hp Outboard

I recall having a issue with that same model in 2003. What it ended up being was the oil pan was not sealing properly. I ended up having to pull the power head and reaming out the bolt holes on the oil pan so it would aline properly, hope this is not your issue. But it is one that can not be dismissed. If they can't find anything simple have them call merc-techservice I'm sure they will remember this issue. Not sure if there was ever a service bulletin.

 

[Jeep Man]

Re: Water in Oil - 2003 Mercury 4 Stroke 75hp Outboard

Even if you have to replace the head gaskets, it's worth it, as replacement of the same would set you back around 4 grand. Might not be a bad idea to do all the gaskets if your pulling it apart.

 

[scjakester]

Re: Water in Oil - 2003 Mercury 4 Stroke 75hp Outboard

Thanks for the reply, I'll be sure to let the tech know about that next week. I cannot find any really good info on the Internet about that particular motor -- either it isn't that popular or they are bullet proof and just don't tear up?!?!? I read that a faulty oil pump or oil pump gasket could cause it, and I also read that just simple winter condensation can cause it. It came out of southern Florida, it would be sweet (SUPER SWEET!) if that were the case, but I'm not going to hold my breath. Has anyone else ever seen condensation get into their 4-stroke outboard's engine oil?

 

[Jeep Man]

Re: Water in Oil - 2003 Mercury 4 Stroke 75hp Outboard

They are good engines, but the reason you probably think they are not popular is that the 90 hp wasn't much more money and many buyers went that way when buying new.

 

[Stephen_12]

Re: Water in Oil - 2003 Mercury 4 Stroke 75hp Outboard

This seems to be a very common issue with Mercury four strokes. A small amount of water accumulation in the oil is normal. I have replaced the head gasket, oil sump gaskets, drive-shaft housing gaskets, oil pump o rings, and various other parts. What made the most difference was cleaning the water pressure relief valve and replacing the thermostat. My pressure relief valve was not opening enough and my water pressure was running about 40 psi which is way too high. My thermostat was stuck wide open and when I replaced it, I started seeing the high water pressure. Once I cleaned the valve, everything went back to normal. But what is normal? If your oil level keeps going up or your dipstick blows out, that's cause for concern and is not normal!

The rest of the work that was performed did not change anything. If you have a blown head gasket, the engine will run poorly and this can be diagnosed with a compression test. Don't be too quick to spend tons of money trying to fix what can't be fixed. I just purchased a brand new Mercury 2012 90 hp four stroke and took it out for the very first test ride on a very cold day this January. Today I removed the drain plug and out came about 5 drops of water mixed with oil before the clean oil came out. No different than my 2005. Below are the current theories on the causes that I have been able to compile based on speaking with two Mercury dealers:

stuck thermostats
prolonged idling
cold weather operation
engine sitting very low on transom
Too much propeller pitch not allowing engine to reach rated RPM
blown head gaskets
damaged oil pump seals
stuck pressure relief valve

Hello all... I purchased a 2003 Pontoon boat last week (fully knowing there was a small amount of water mixed in the oil). I basically purchased the boat and the owner gave me the outboard. He said it was running fine over the fall, he parked it on his boat lift and went to start it a few weeks ago, when he checked the oil there was some water mixed in.

He said there were no whistles or alarms going off and that he checked the oil the last day he took it out (in December), and it was fine. He said all he could figure is that it had to have happened either on the way back to his boat lift that day or somehow while it was up on the boat lift itself?!?!?! I'm not going to attempt to start it, I'm taking it straight to a Certified Mercury Service Center and get a technician to go through it for me next week. I am kinda hoping it can be repaired (instead of repowered) but like I said, the motor was just a freebee either way, I only paid for the boat itself.

Anyone have any ideas on what could be wrong with it?

-Jake
South Carolina