4 stroke engine making oil?

[roujoh]

I have a 1999 Evinrude 70hp fuel injected 4 stroke outboard engine. I regularly change the synthetic oil twice a year. When I put the new oil in the level is right where it should be and by the time I change the oil it is over full. The oil smells like gasoline. If the fuel was getting by the rings while it is running it should be running very poorly, but it runs like a top. Any ideas?

 

[suzuki40]

Re: 4 stroke engine making oil?

I just had the same problem with my 125 mercury.<br />It was the diaphram that went bad in the ..I think they called it the "VRO" They told me it was a common problem. replacement cost me $350.00 parts and all.<br /><br />Hope this gives you an idea to check,If im calling the part the wrong name, please someone correct me.<br /><br />suzuki 40

 

[outboardjake]

Re: 4 stroke engine making oil?

I have seen a couple of bad low pressure fuel pump diaphrams. The pump is located on top of the valve cover.

 

[neumanns]

Re: 4 stroke engine making oil?

roujoh...I read your post with great intrest because we share the same engine, so I pulled out my service manuel and could find no logical explanation. Hopefully you will have a good diagnosis and will notify us of your results so that should i ever have same problem perhaps I will know where to look. I think I will go smell my oil before I take her out tomarrow Sorry I could not help you.

 

[hondon]

Re: 4 stroke engine making oil?

Yes your four stroke engine can "MAKE " oil under certain conditions.Trolling in exceptionally cold water for extended periods can do it.Short runs consistantly can also do it .By and large these engines will always make a little oil .Under ordinary conditions the fuel that is makeing that oil is evaporated in the oil pan and the fumes from that evaporation are fed back to the intake by various means.That is why all four stroke manufactures recommend an annual oil change and are not going nuts recommending synthetic oils.

 

[lakensea]

Re: 4 stroke engine making oil?

Too much low speed idling during the break-in period will also cause this. Get rid of the synthetic oil and change it more often.

 

[lakeman1999]

Re: 4 stroke engine making oil?

During the hot summer that I first purchased my latest lawn mower (tractor), When I went to mow my lawn, I made the regular before starting oil check, and found the oil level way too high, and exceptionally thin. When you live out of town (no gas stations near) at the lake, with two boats, two vehicles, a lawn mower, and other gas powered tools, as well as a sawmill, you keep a few 5/6 gallon cans of gas on hand. So I decided that after my last mowing session, and preparing to make a trip to town I filled the tank on the mower, so I would have another empty too fill in town and bring back to my fuel bank. I finally decided that as the day heated up (98+) the gasoline in the full tank expanded, and tank being full there was no place for it to go, except thru the carb and and into the crankcase of the engine. I never leave the mower tank full between mowing sessions after that. Is this a possibility with out boards? Possibly the engine on occaision comes to a stop with an intake valve or two partially open?

 

[JB]

Re: 4 stroke engine making oil?

Howdy Roujoh.<br /><br />This has been common in 4 stroke outboards, mostly EFI Yamahas, but yours is the second DF70 I have heard of.<br /><br />Nobody has come up with a definitive "fix", but Yamaha tells people to run their engines harder, particularly during break in. That seems to work.<br /><br />My DF70 hasn't done it. I use Mobil 1.<br /><br />I think Hondon's explanation is correct. The oil must get up to operating temp and evaporate any gas that gets into the crankcase. Cold operation and long idling periods wont do that.<br /><br />How does the fuel get there in the first place? Most people assume that it gets by the piston rings during operation. I don't think so. The high pressure pump/vapor seperator maintains about 30psi pressure after the engine is shut down and that pressure has to go somewhere. It may leak past injectors or some other excellent, but not perfect seal.<br /><br />You might get in the habit of draining the vapor seperator reservoir as explained in your Owner's Manual when you shut her down at the end of the day.

 

[roujoh]

Re: 4 stroke engine making oil?

I had talked to another friend of mine that has a Honda 40 hp 4 stroke and he was having the same problem. His dealer had no explanation for the problem either. I do a lot of cold weather trolling and short trips in the late winter and early spring when I go Steelie fishing. I have had the motor just over 3 years and that is the only complaint I can come up with after 320+ hours of run time. I usually change the oil about every 50 hours. Thankyou for your input.