2003 90hp 4stroke making oil

boating4fish

Recruit
Joined
Mar 8, 2010
Messages
4
When I found extra milky looking oil on the dip stick I was sure I had a water leak, but after reading some threads I think I was doing everything right(or wrong) to "Make oil". I was trolling on the motor for many hours in 50 degree water with a thermostat which I think was sticking open on a lake with a 5mph limit.

It seems like everyone correlates milky oil to water contamination I wonder can gas or something else also turn the oil milky?

This is why I ask, I changed the oil and filter three time to get rid of the old junk. I then ran the engine for an hour or so on the lake just like I was doing before and checked the oil when I got home. There was little more oil then when I started, started at 1/2 and it was 3/4 up the hashing. It was mostly clear but there was a small amount of white bubbles. I left the engine down and checked in the morning the oil was all milky and up over the hashing. The oil smells a little like gas, but I cant tell for sure. I would think if it was water being emulsified it would not continue without the motor running or am I wrong to think that?

I did not know about the thermostat yet, but I was pretty sure how I was operation the engine was causing the problem but before running that test I checked the compression and ran water through the flushing port for over an hour so I am pretty sure there was no obvious paths for water.

Changed the oil again three times, checked the thermostat, it got stuck open the first time in hot water, but started working after I pushed it closed so I replaced it. Checked the fuel pump and it was working OK. I changed the plugs as well.

I ran the engine again for a couple hours up on plane and the oil looks good.

While running I also checked the RPMs at WOT. ~5200 with the drive all the way down and 5600 trimmed up for max speed.

Besides sending the oil in for analysis is there anything else I can do to confirm it was fuel not water getting in?
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: 2003 90hp 4stroke making oil

This question is exactly the same as the thread you started a few minutes ago...

THIS ONE!
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,795
Re: 2003 90hp 4stroke making oil

Go to the archives. This subject has been addressed many times.....seems to be a normal occurrence.

Mark
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,931
Re: 2003 90hp 4stroke making oil

Go to a Yamaha dealer and get the 150 degree t-stat and and see if it cuts down your crankcase condensation and when trolling trim the engine level. If speed is to fast trimed level install a trolling plate behind prop.
 

boating4fish

Recruit
Joined
Mar 8, 2010
Messages
4
Re: 2003 90hp 4stroke making oil

sorry for the double posting, I got an error message that I was not logged in. when I logged it I was still at the edit screen so I did not think it posted.

Yes there are other posts regarding making oil, but the one I reviewed seems to all say milky = water. In the seconds to needed to log in I thought the title of the second post was a better title so that is why the name changed.

I had thought about the trolling plate as well. I am sure it would increase the RPMs but not enough to keep me from making a few laps around the lake.
 
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