F115 Water in Oil

[Deltatango]

Hi,

I notice lost of posts on this forum about water in the engine oil, well, here's another one.
2003 Yamaha F115, 7-800hours.

Carried out a scheduled oil change around 2 months ago, noticed that the oil was just slightly opaque. Ran the motor for around 4-6 hours over 3-4 seperate occasions, mix of idling and high speed. Parked the boat up for a month.
Checked the oil before heading out for a dive on the weekend and found it to be emulsified mid brown latte colour. Changed the oil and filter and ran for 15min on the earmuffs.
The oil was starting to appear very slightly opaque so I figured ongoing problem and shut it down, although now I guess it is possible that this was residual emulsion being picked up in the oil.
compression test 190-195psi at cranking speed.

Pulled the lower unit to have a look at the shaft, appears to be the model with the two seals on base of oil pump as i can see two very shallow grooves polished in the shaft just below the spline, the lower slightly deeper.

No noticeable oil fling in the lower leg or on the shaft, no noticeable dribble of oil from drain in lower unit.

Pulled the powerhead to have a look at the top of the oil pump/underside of the powerhead.

No noticeable sign of water having travelled up through the oil pump. Presumably the path that water takes is up the shaft, through the oil seals noted above, through the shaft spline and cascade/flung out across the top of the the oil pump housing and down into the sump? Presumably not physically entering the oil pump? Please correct me if im wrong here.

No sign of damage to the powerhead base gasket or mating surfaces.

Large blob of emulsified oil sitting on top of the powerhead base gasket in the aft, port side. See picture attached.
Heavily emulsified oil seeping down from the powerhead on the aft, port side. Note only from the aft of the two ports See picture attached.

Strip down the powerhead, go looking for corrosion or head gasket damage? No sign of corrosion in waterways in base of head/midsection. Is run in salt water but always washed out.

Thanks in advance for help.

Phil

[Deltatango]

Bounce........

[bajakeith]

water in oil

Check and replace the thermastats !! it's called Wicking and I see it a lot !! when you open the therm cover's and one or both are stuck open,, that's your problem ...also see guys turn off motor and start tilting without waiting a min for water to drain from pwr head..not good !!! and if it got HOT,, possible head gaskets......keith & the famous lil Tasha

[Deltatango]

Thanks for the advice.

I seem to recall that in the past i have had an error code for running over cool when a thermostat has failed open. Didn't get any error codes on this motor, plus the change in the oil was very sudden, basically in the space of a couple of hours running time.

Phil

[Deltatango]

Checked the thermostat this evening, operating normally. No sign of corrosion/salt build up.
Phil

[Deltatango]

Cannot say I have recieved a flood of reponses on this...?

Thermostat tested all good.

So,

I have stripped down the power head (as the motor is 10yo and 700hours plus I figured a regasket and general 'birthday' was probably in order anyhow). Head gasket in good condition, salt build up minimal, corrosion minimal ie leak not here. So have ordered a new oil pump assy and will look at either sleeving the shaft or shimming the oil/water seals on the shaft as it seems the only likely culprit.

Phil

[ausnoelm]

not 100% sure stripping it down was the right way to go about this, I reckon (and my opinion only) that better trouble shooting first would have been in order, you may re-assemble it and not fix the proble, or indeed, you may fix it, but you will not know what you fixed.

[Deltatango]

Hi,

Thanks for the response.

Some advice on better troubleshooting would be very useful, in case, when I reassemble and run, the motor continues to have problems with oil contamination.

So you can be specific, please note the following 'history':

The motor has no prior history of water contamination of the oil, has been operated in a consistent manner on the same boat for the 6 years I have owned it, that the compressions are good and the thermostat operates as per spec.


Phil

[rodbolt17]

its actually fairly easy.
if the plugs show no signs of water burn then most likly the head gasket is good.

odds are high its not an oil pump sealing issue or you would be posting about oil leaks.

remember the oil pan and ex stack is also water cooled and not pressurized.

[bajakeith]

water issue

and if/when water is passing in the cylinder,, it will be a very clean looking spark plug....not rusty unless happening for a long time....the most common reason for water in the oil on a four stroke is stuck open therms..........

[Deltatango]

So,
Have replaced oil pump and sleeved slight groove in prop shaft. Replaced head gasket. Replaced thermostat. Absolutely no sign of water in cylinders. Several oil changes later still rapidly becoming emulsified.
Have run water through flush with motor stopped and sump drained and sump plug out. No evidence of water getting in while on flush.
Short of stripping down again and pressure testing head and block and leg I'm not sure of what should be next step.
Anyone got any bright ideas?
Phil C

[Deltatango]

Bounce
Bounce

[rodbolt17]

once a leakdown test is done to eliminate a cyl head gasket I would check the ex cover for leaks.
then strip down the oil pan assy and check the gasket surfaces with a straight edge.
we do see the occasional warped surface.

[Deltatango]

Logged back into this forum to see if there was any help available on another problem on my f115. Noticed that I hadn't posted on the resolution of the making water problem.

So, here it is: The thermostat was the problem. I tested that it opened in hot water. What I didn't do was check that the thermostat was actually opening at precisely the correct temperature. It 'failed' by opening at less than 10degrees too cold.

bajakeith you were right. Seems that this model maybe doesn't throw an 'over cold' error message.

[boscoe99]

Thanks for the feed back.

F115's were known to run on the cold side even in the best of conditions. Later model F115's were delivered with a thermostat that opened at a higher temperature to get the motor to run hotter.

You might want to consider the later part number thermostat if your replacement was the original thermostat.