Merc 4 Stroke - Gas in Crankcase

[Jud Hamblett]

Engine is a 2002, 115 HP four stroke. Reported this problem earlier to the forum. Just came back from a 250 miles run across the strait of Gibraltar from Morocco and up the coast of Spain. Am now at 150 hours and oil was waaaay high on the dipstick. Carefully measured the drained oil and came up with more than a whole extra quart! - 6 instead 5. Only added 5 at the last change. There was about 30 hours run time from the last oil change. <br /><br /> Definately not water, has slight fuel smell and was dirty. Could not burn it with a match though. Can someone out there shed some more light on this? How can fuel access the crankcase – fuel pump diaphragm or seal, unburned fuel at shutdown leaking past the rings….?? I’d say I run around 1,500 and 4000 rpm about half and half. Love to hear from Mercury on this…. Can’t find anybody here in my sandbox to help. <br /><br />Advice???

 

[skootter2]

Re: Merc 4 Stroke - Gas in Crankcase

I have a 2002 90hp 4-stroke, I am having same problem with gas in the oil. Any resolution for you? Please e-mail me. skootter2@hotmail.com

 

[JB]

Re: Merc 4 Stroke - Gas in Crankcase

Do a search. This has come up several times, and on the Yamaha version, too.<br /><br />The fix is to replace the thermostat with a new 140* TS.<br /><br />Good luck.

 

[The Marine Doctor]

Re: Merc 4 Stroke - Gas in Crankcase

Yes..that is the answer..the T-Stat is allowing the engine to run too cool.<br /><br />TMD

 

[Jud Hamblett]

Re: Merc 4 Stroke - Gas in Crankcase

Skooter, Am now at about 175 hours and the oil level issue appears to be stabilizing. I changed the oil and did another 300 mile trip up the coast of Spain running it as hard as I could given the sea conditions. I think the issue may be related to break in. I have changed my oil and filter 4 times since new. <br /><br />Recommendation: Break in the motor according to the manual. After that, get the revs up and the engine working hard whenever you can. Check the oil and change it as often as necessary - whenever it gets real dirty (meaning diluted) OR rises more than an inch above the Full line on the dipstick.<br /><br />If you go with the Thermostat recommendation, which certainly has merit (effectively burns off the gas), I would have the dealer install it in order to keep the warranty valid.<br /><br />Good luck, Back to my sandbox....

 

[Philip Marsteller]

Re: Merc 4 Stroke - Gas in Crankcase

I have a number of 2001/2002 Mercury 75/90/115 4 strokes. We are having serious problems with fuel in the oil, oil level rising, engine failure due to lack of lubrication of #1 rod end bearing. Is any one else experiencing these problems?

 

[The Marine Doctor]

Re: Merc 4 Stroke - Gas in Crankcase

The engine is running too cold. It stays in cold start mode and floods. This puts fuel into the crankcase. Washes away the lubricating qualities of the oil and aerates the oil as well. Causing premature wear.<br /><br />Change the T-stats<br /><br />TMD

 

[Jud Hamblett]

Re: Merc 4 Stroke - Gas in Crankcase

All, The factory manual shows thermostat opening operating temperature to be 140 degrees F. <br /><br />Is the suggestion to use a thermostat with a higher degree rating or make sure the original is working at the specification temperature?

 

[louchic1]

Re: Merc 4 Stroke - Gas in Crankcase

I just purchased a Hurricane SD 187 from a fella in Fargo ND. this spring, my first boat.
It's powered with a 2002 Mercury 115 Four Stroke EFI. It's getting (a lot) of fuel in the oil. I have changed the low pressure fuel pump and the thermostat. I did see that the new thermostat was a 50c same as the one i removed, (that's 122f) seems a little cool to me but i am not that familiar with outboard engines. One thing i do know is that i am falling out of love with this one in a hurry....
I am going to guess a quart of gas in the oil after maybe four hours of running.
Any one have any ideas?
This engine seems to run good, starts up nice and seems to have full power. I don't know anyone else with the same configuration as this but i read up on enough engine tests on the Mercury site to know my WOT, prop, top speed and RPM are in the ball park.

 

[Superdave66]

Check the fuel pump. Pull the pump out of the engine, clamp off lines to the carbs and pump the inline bulb. If gas flow out around the end that goes into the engine, you need a new pump. My 50hp 4-stroke will dump 2 quarts of gas in the oil overnight if I leave the gas line hooked up.

 

[GA_Boater]

Check the fuel pump. Pull the pump out of the engine, clamp off lines to the carbs and pump the inline bulb. If gas flow out around the end that goes into the engine, you need a new pump. My 50hp 4-stroke will dump 2 quarts of gas in the oil overnight if I leave the gas line hooked up.

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