Water in the Crankcase of a fourstroke?

[FishTy]

Want to get some advvise.

I have a 2005 90hp Mercury fourstroke, and I have a problem with water in the crankcase.
a local dealer has my boat, and they called me the this morning saying that a little bit ( up to 3 tablespoons) is normal if run in cold water.
Every time I go out fishing I check my oil and it seems like at the dipstick.
its always higher than last time!.
I'm just worried that they are not finding the problem, and making excuses!

Any one else have this problem?

should I be worried?
any advise would be GREAT!
Thank You

[Jedcraft]

Do you open it up much or run it slow like troll speed? I had an 8hp Honda that would build up fuel in the crankcase if I did nothing but run at troll speed for days on end. Did it good to run it wide open for awhile every now & then. The oil was not milky though.

[FishTy]

Do you open it up much or run it slow like troll speed? I had an 8hp Honda that would build up fuel in the crankcase if I did nothing but run at troll speed for days on end. Did it good to run it wide open for awhile every now & then. The oil was not milky though.
My 90hp is always almost half throttle or better! I use my 9.9 for trolling
My oil is not milky or anything. just seems like my oil is growing..
When I change the oil the water comes out of the drain hole first.. More than I would like to see, thats for sure!

[Two Ducks]

Check your thermostat. I had a Honda do the same and the thermo was stuck open. Easy fix. Good luck.

[FishTy]

Check your thermostat. I had a Honda do the same and the thermo was stuck open. Easy fix. Good luck.
Actually the first time it went in to the shop. that is what they said.
they replace it.. with no help!

[marys netter]

Don't know about big motors:(but have had two Honda BF100's[8 hp] trollers with that problem and now my T-8 has the same problem {1100 hrs mostly trolling} The bottom line was it was fuel dilution not water and if I changed oil occasionally I had no consequences. Hours on end of troll speeds even with the occasional throttle blips and unburnt fuel adds to crankcase volume.
Crankcase oil can only gain volume from two sources,either from the water jacket or the rings [If ya don't over fill:cool:]:twocents:
Dave

[ICHTHYDEMON]

Don't know about big motors:(but have had two Honda BF100's[8 hp] trollers with that problem and now my T-8 has the same problem {1100 hrs mostly trolling} The bottom line was it was fuel dilution not water and if I changed oil occasionally I had no consequences. Hours on end of troll speeds even with the occasional throttle blips and unburnt fuel adds to crankcase volume.
Crankcase oil can only gain volume from two sources,either from the water jacket or the rings [If ya don't over fill:cool:]:twocents:
Dave

I'd lean towards fuel dilution as well. Some 4 strokes are prone to "making oil".

Babying a 4 stroke won't make it any better either. You need to run the wee out of them on occasion. I try to run WOT for at least a few minutes every time I take the boat out.

[Lockjaw]

I had the same thing happen to my 00 Yamaha 100 hp, took it in to the shop and the first thing they checked was the thermosat.It was stuck open a little so we changed it. That did'nt stop the water getting in the oil. It was the lower gaskit leaking water. It was still under warranty at that time so I only payed for the new thermosat.


L J

[FishTy]

I had the same thing happen to my 00 Yamaha 100 hp, took it in to the shop and the first thing they checked was the thermosat.It was stuck open a little so we changed it. That did'nt stop the water getting in the oil. It was the lower gaskit leaking water. It was still under warranty at that time so I only payed for the new thermosat.


L J
Thats what there doing to mine, is pulling the power head to replace the lower gaskets..... I hope that works!!!

Water in the oil,, makes me think of car motors.. a crack in the head or head gasket...

Hoping that fixes it !!

[weekender]

Head Gasket, Base Gasket, Thermostat gasket can all get water into the oil. Is it enough water that the oil gets milky?

[Lockjaw]

Head Gasket, Base Gasket, Thermostat gasket can all get water into the oil. Is it enough water that the oil gets milky?
It was for mine. I changed the oil and made one trip and the oil was milky looking.
Weekender, when you first start a Yamaha 100 hp they rattle for a short time.I was told to exspet this when I first got mine.

L J

[Empire]

I had the exact same problem with my 2002 115HP Mercury.

The oil has chemicals in it to suspend the water molecules rather then keeping them seperate. When water is suspended, the oil turns milky.

I took my motor in for work. They changed a few gaskets in the leg but did not solve the problem. I believe the problem was from running the motor for short distances in cold temps and not letting the engine warm up and burn off the water that condensed in the crankcase.

Now I let the motor get completely warmed up each trip. I also changed to synthetic oil (Mobile EP10W30). No problems in the last two years.

[timinthegorge]

My '06 115 4stroke Merc did the same thing, and it started out with the Merc synthetic in it. I make sure it's good and warm before heading out, and I always run it full throttle for awhile on each trip. No problems since then (knock on wood). :twocents: