fuel in the oil?

[dport]

I have a Nissan 25hp 4 stroke EFI, and without looking I think it is a 2002. I purchased it used last year and this will be my first full season with it. I believe it has seen a good deal of sitting until late last year. The previous owner said he was the original owner and claimed he had less than 40 hours on the engine. I have replaced the water pump, the lower gear box oil(last year and this year), spark plugs, fuel filter, and I changed out the oil last year when I first got it, but I had not yet changed the oil this year. I had put about 20 hours on it last year, and was going to change after another 20 hours.

So I went to check my oil before I set out for the first time this season. (I know, I know, I'm very late.)

I took the dipstick out the oil started gushing out. As I was cleaning up the mess I noticed the oil had a strong smell of gasoline. I had never noticed that before, and while I'm an outboard newbie, I know that that's not good for a 4 stroke engine. But, I checked the smell of new oil just to make sure it wasn't a smell characteristic of the oil itself. It wasn't. So I drained the oil, figuring at the very least that I'll need to change the oil.

Is there a most likely cause for something like this? Are there any known issues? I can't think of any common areas for fuel an oil other than where the fuel pump mounts. Any ideas?

Thanks!

 

[TOHATSU GURU]

Re: fuel in the oil?

The first year for EFI is 2007 so........I'm sure you have a carburetored model. Fuel in the oil is common on all, four-stroke brands andmodels to some degree, depending on the environment and usage. Change the oil every 50 hours and don't worry about it.

 

[Skinnywater]

Re: fuel in the oil?

The first year for EFI is 2007 so........I'm sure you have a carburetored model. Fuel in the oil is common on all, four-stroke brands andmodels to some degree, depending on the environment and usage. Change the oil every 50 hours and don't worry about it.

"Oil gushing out the dipstick tube" is common?

 

[TOHATSU GURU]

Re: fuel in the oil?

Only when the engine has not had any care at all.

 

[Harker]

Re: fuel in the oil?

How would gas fill the crank case? Stuck floats? Bad pump? Bad valves? Sounds like it was under pressure too. Was too much oil put in when you changed it last?

 

[TGuy]

Re: fuel in the oil?

As the guru said, it's actually very common in today's 4-stroke outboards, regardless of brand. You see it more when people are using their motors at slow speeds for long periods of time because the engine does heat up enough to get the rings to seat which allows the gas to pass the rings and get into the oil pan.

It's so common in fact that the industry developed a new oil just for outboards called FC-W oil (four-cycle, watercooled). The new oil doesn't solve the problem, but rather it helps reduce the effect of the gas in the oil. The biggest problem of getting the gas in the oil is that it reduces the viscosity of the oil. The FC-W rated oils minimize that reduction of viscosity through various additives. So bottom line is, if you do a lot of slow speed cruising/trolling, you'll need to change your oil more often and use an FC-W rated outboard oil (instead of a car oil).

Or go faster...

 

[dport]

Re: fuel in the oil?

The first year for EFI is 2007 so........I'm sure you have a carburetored model. Fuel in the oil is common on all, four-stroke brands andmodels to some degree, depending on the environment and usage. Change the oil every 50 hours and don't worry about it.

You're right it is a carb model. My mistake.

Thanks all.

 

[Harker]

Re: fuel in the oil?

Well now, that makes sense. It seems they would reccomend a hotter plug or a warmer thermostat rather than develop a new oil. I have a 25 Honda on my pontoon and do a lot more "putting" than going fast (relative term for 13mph wot). I haven't "made" oil yet with it.

 

[dport]

Re: fuel in the oil?

How would gas fill the crank case? Stuck floats? Bad pump? Bad valves? Sounds like it was under pressure too. Was too much oil put in when you changed it last?

I didn't overfill it. I'm very paranoid and thus careful about these things.

Under pressure? I would say it was consistent with it being overfilled to the point that the dipstick was below the oil level.

 

[dport]

Re: fuel in the oil?

Only when the engine has not had any care at all.

I'm curious if I should be doing more to care for the engine.

 

[eipeldau]

Re: fuel in the oil?

I'm not sure this applies to your issue, but maybe check your fuel pump diaphragm. I lost a BF100 years ago, because this diaphragm broke and LOTS of fuel suddenly mixed into the oil.
Best wishes!

 

[Harker]

Re: fuel in the oil?

Seems like the entire block would have to be full to "gush" out. Wouldn't that make it hard to crank over?

 

[TGuy]

Re: fuel in the oil?

came across an interesting article that was written back when FC-W was still under consideration / development (below was copied/pasted from the website):
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According to NMMA's Schultz, some issues need to be addressed before official licensing begins. "First, is the problem of viscosity dilution," he says. "Four stroke outboard engines often have long periods of idle, and in cooler water the oil tends to accumulate enough fuel which then dilutes the viscosity and may lead to excess wear unless the additive package is fortified with extra surface active ingredients, like ZDDP, which contains phosphorous and zinc. In cars, the operating temperature is high enough, around 220 degrees Fahrenheit, to 'cook off' the fuel but in marine engines the operating temperature is between 120 and 145 and at that temperature the fuel does not get vaporized as easily.

"Automotive additive packages in API SJ oils, which is the category currently recommended for most of today's marine four stroke engines, can handle the oil dilution issue. But with substantial reductions in the percentage of ZDDP in future automotive engine oil categories under active consideration by the auto industry, marine applications may be placed at risk," says Schultz.

"And we can't simply increase the thermostat temperature because that will cause the second problem," continues Schultz. "At about 160 degrees F. salt water starts to recrystalize inside the cooling system and begins to form stalactites and stalagmites and impede the flow of coolant. Some ingenious technological solutions have been devised, such as rerouting the oil through engine hot spots to give it the ability to shed fuel. But cooling system problems can be a major issue."
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And now you know why they don't put hotter t-stats in the motors. Every action causes a reaction

If you want to read the full article, I found it here:
http://www.smartsynthetics.com/articles/future_of_two_stroke_four_stroke_outboardmotors.htm

 

[Harker]

Re: fuel in the oil?

Hmmm..never thought about saltwater..I live and breathe in Michigan. I just put synthetic oil in my 2004 Honda..now I have to try and find the one for marine use? I'll just make sure I go wot all the time...

 

[dport]

Re: fuel in the oil?

I'm not sure this applies to your issue, but maybe check your fuel pump diaphragm. I lost a BF100 years ago, because this diaphragm broke and LOTS of fuel suddenly mixed into the oil.
Best wishes!

I had thought about replacing the fuel pump just in case.

 

[eipeldau]

Re: fuel in the oil?

I'd encourage you to just visually check the diaphragm. If it's cracked, this could be the cause to your problem. If you have a shop manual, it will be pretty simple for you to perform the task.
Good luck!