2005 F250 4 stroke making oil

[wavetamer]

have a low hour Yamaha 250 which I just purchase on a Grady but have noticed it making oil. The outboard has gone from a warm water climate to a colder water climate and I suspect because its running cold its running rich. Spoke with Yamaha techs and they have been installing a hotter operating thermostat made by Suzuki that they say corrects the problem. Has any one else had this experience and what did you do to correct.

[rodbolt17]

first you do a leakdown test.
then you insure the t-stats are working.
and check that it can reach 5800 RPM.

[wavetamer]

all those pass and that is not the issue

[boscoe99]

Assuming that the rings are seated, the thermostats are working correctly, the motor is properly propped, etc., what about the fuel injectors? Have they been tested to ensure they are not flowing too much gasoline?

Has an air/fuel meter been installed to verify that the motor is indeed running too rich?

Have you tried a heavier weight oil to try and get the rings to seal any better?

If you are absolutely positively sure that everything is perfectly fine with the motor, and you are not willing to change the oil more frequently to combat the fuel dilution issue, then there is nothing stopping you from trying a hotter thermostat. If it works for you, or does not work, then let us know. That is how we all can learn.

I see that Suzuki has an optional thermostat that is 11 degrees C hotter than the standard thermostat. I am guessing that the optional thermostat is intended to solve a making oil problem. Yamaha used a different (hotter) thermostat in some models to combat the making oil issue.

We look forward to hearing your results.

[wavetamer]

thanks for all your reply's, its seems making oil to be more of an issue here on the pacific west coast. Yamaha actually stocks the Suzuki thermostat and most are going that way. I want to correct the problem but don't want to create a bigger problem or kill the life of the outboard by running it to hot so im trying to under stand what is going on. you make a valid point about the fuel system /injectors which haven't been checked.

[boscoe99]

If the hotter Suzuki thermostat does not adversely affect a Suzuki then I don't see it adversely affecting a Yamaha. And if your local mechanics have been using it with success in Yamaha's then what more evidence is needed?

I personally don't think it will be harming the motor. I would have no qualms about using it. Even with a Suzuki thermostat installed in your motor, in the conditions you are boating in, your motor might still actually run cooler than an F250, using regular Yamaha thermostats, that is being operated in 88 degree F water.

Think about big diesel trucks going down the highway in winter conditions. They are running so cool that they sometimes have to have big flaps over the radiator to try and get the engine temperature back up to optimum conditions. Think of the hotter thermostats as big flaps. Different requirements for different conditions.

Same with airplanes. In the winter time it is normal for oil coolers to be blocked off so that the oil temperatures will be hotter than they would otherwise be.

[wavetamer]

when I first noticed thought maybe reading it wrong, but was checking correctly, then did what Rodbolt17 also suggested everything checked out ok. So will install new stats and see if it changes. I don't mind changing the oil a little more often if I have to . On the injector issue is there something worth while to running through them to clean or better of to remove and insp

[99yam40]

Monitor fuel pressures to make sure they stay in spec.
as far as injectors, you can have then tested and cleaned .
they will give an as found and as left report

I am not sure if they do flow rates, but I think they do along with spray patterns and leak checks
if pressures are out of spec it can affect amount thru the injectors if low or over pressured

[wavetamer]

finally got to taking the stats out and replaced. both were found stuck open position, im really hoping this is what was causing engine to run cool and make oil.

[boscoe99]

That will do it.

Damn, I was really hoping for a report about Suzuki alternate thermostats being installed in a Yam F250.

[fairdeal]

Damn, I was really hoping for a report about Suzuki alternate thermostats being installed in a Yam F250.

yes, so often a disconnect between vague internet b.s. and tangible hard facts.

This is the SM spec on the stock thermostat in my F225



Now, in my minimum 75 F operating waters, that results in an "engine temperature" of up to 205 F

we need more data.....

[boscoe99]

yes, so often a disconnect between vague internet b.s. and tangible hard facts.

This is the SM spec on the stock thermostat in my F225



Now, in my minimum 75 F operating waters, that results in an "engine temperature" of up to 205 F

we need more data.....

Let's not go comparing water temperatures to engine temperatures. If your motor is connected to an NEMA 2000 device, which I think is the case, you are seeing block temperatures on the display. When you have some time on your hands maybe you will install a water temperature sensor to see how the water temperature correlates to the block temperature.

[wavetamer]

Did install the Suzuki thermostats so we will see how oil level performs. the thermostats had 350hrs and were defiantly failed open and probably caused the outboard to run to cool. Tried to up load pic of the STATS but not having any luck. Will put some hours on her and monitor oil level.

[fairdeal]

If your motor is connected to an NEMA 2000 device, which I think is the case, you are seeing block temperatures on the display.

correct.

When you have some time on your hands maybe you will install a water temperature sensor to see how the water temperature correlates to the block temperature.

On my to-do list; would love to have real-time "mapping" of the engine temps.
looking for an "inexpensive" way to do it via N2K.

[pstephens46]

Why does an engine make oil when running cooler than normal? If it was the fuel mixture, couldn't the ECU compensate? Do engines make oil at start up for a brief period of time until temp rises?