new 5ph 4stroke, gas in oil, what to do?

[porta-homer]

I bought my first outboard in April, a 2004 nissan 5hp 4 stroke. We have had it out less than 50 hours this summer and I have noticed that the oil smells like gas. What could be causing this, and is this anything I can fix without taking it to a dealer?

 

[JB]

Re: new 5ph 4stroke, gas in oil, what to do?

If it's a Nissan, why did you post in the Mercury forum?<br /><br />I will moved this to the Tohatsu/Nissan forum.

 

[porta-homer]

Re: new 5ph 4stroke, gas in oil, what to do?

Because as I don't know much about motors, one thing I do know is that the 5hp nissan is exactly the same motor as the mercury (except mercs are painted black)<br />I posted on the mercury board because there are 25 times as many posts there = better chance of response<br />thanks for the help

 

[TOHATSU GURU]

Re: new 5ph 4stroke, gas in oil, what to do?

If you have gas in the oil the most likely cause is that the engine is not reaching operating temperature, allowing fuel to seep into the oil. High altitude, cold water temperature, excessive idling and the wrong grade of oil could be the cause. Or, you could have a bad seal.

 

[JB]

Re: new 5ph 4stroke, gas in oil, what to do?

Actually, Homer, both the Nissan and the Merc are made by Tohatsu.<br /><br />The reason there are so many posts in the Merc forum is that there are many, many more Mercs with trouble than Tohatsu-made engines.<br /><br />The reason we have this forum is to serve users of the engine brands named. . .Honda, Tohatsu and Nissan. Smaller numbers of posts get more attention from helpers, anyway.<br /><br />Believe it or not, we do know what we are doing. <br /><br />Among other likely causes of gas contamination in the oil are incomplete seating of the rings during break-in, extended periods of idling or very slow operation, and other failures to reach full operating temperature.<br /><br />Run the engine hard for several hours, check actual engine operating temperature, and you might look into a higher temp thermostat.<br /><br />Good luck.

 

[Drowned Rat]

Re: new 5ph 4stroke, gas in oil, what to do?

I'm surprised you would have that problem on a new Nissan. Are you sure there is actually gas in the oil or does it just smell that way? I would check the viscosity of the oil first to see if there really is a problem. How many times have you changed the oil since new? A small amount of leakage could be considered normal during the break-in period. Good luck.

 

[porta-homer]

Re: new 5ph 4stroke, gas in oil, what to do?

thanks for the help. I'm not sure if there is actual gas in the oil but it sure smells that way. I haven't changed the oil since i bought it new in April and have had it out about 30 hours.

 

[Paul Moir]

Re: new 5ph 4stroke, gas in oil, what to do?

Sounds like you're 10 hours overdue for an oil change. Consult page 25 of your owners manual.<br /><br /> Owner's manual, click here

 

[radsrh]

Re: new 5ph 4stroke, gas in oil, what to do?

If you have that much time on the motor and you think you have gas in the oil, what is the oil level? With 30hrs on the motor and a noticeable gas leak into the oil the level should be well above the full mark, I would think that before the vescosity would change much you would have gas/oil out the top of the dipstick tube.

 

[Drowned Rat]

Re: new 5ph 4stroke, gas in oil, what to do?

Prota-homer. Definitely time for an oil change. If that is the original oil, then I would expect some gas leaked in during the break in period. Change the oil and I bet it solves the problem.<br /><br />Radsrh. An change in oil viscosity will be evident when checked with a visgauge even if the oil looks and feels completely normal. Very little fuel is needed to thin the oil.

 

[JJerry]

Re: new 5ph 4stroke, gas in oil, what to do?

Hello. My cousin and I recently bought a Nissan 9.8 4-stroke outboard. We are still in the break in period (currently at the 6hrs) We go fishing every week and use the motor any where from 30mins to 1hr total for the day. We have already changed the oil twice (from the 4hrs in the break in period) due to gas getting into the oil. We are using Castrol 10w30 oil and filling the oil just below the full mark on the dipstick (right below the half X on the dipstick). Yesterday after coming back from fishing, the oil level is above the full mark and there is a smell of fuel. The only idling we do is the initial warmup about 3-5min and then the rest of the time its below 3/4 throttle and a few sec. idling as we are dropping anchor. We also run the fuel out of the engine after we are done for the day. Does this sound normal to you guys like part of the breakin period as stated above? The water temps are in the upper 60s yesterday. Any info is gretly appreciated. Thanks,<br />Jerry

 

[TOHATSU GURU]

Re: new 5ph 4stroke, gas in oil, what to do?

As you have described it...it's not normal. While some fuel is to be expected to wind up in the oil during break-in, what your getting sounds way outside of normal. You need to get it into a dealer for warranty evaluation.

 

[JJerry]

Re: new 5ph 4stroke, gas in oil, what to do?

Thanks Elvin for replying.<br />After rereading my post I noticed that I did not include how much the oil level was on the dipstick after running it. So before I ran the motor I changed the oil and filled it just below the half X mark on the dipstick from full. After running it this past Saturday the oil level on the dipstick is now a half X above the full mark. I hope didn't imply that the oil level was completely filled to the top. Anyway my question is during breakin period, what would be considered normal amount of gas entering the oil tank? If I initally filled the oil to the full mark and the gas got in the oil tank, and the level was say half X above the full mark and remained there until the next oil change (the level never increasing) would that be normal? I will be calling the service center today to get more info on warranty evaluation. Thanks again Elvin for your quick response.<br />JJerry

 

[TOHATSU GURU]

Re: new 5ph 4stroke, gas in oil, what to do?

Jerry,<br /><br />First, it's really unlikely that there is a problem. As the series of above posts point out, their are a number of normal things that can cause the fuel to wind up in the oil. And there is no hard and fast rule about how much over what period of time would be normal. It's more a matter of it being obviously full of gas after some hours(meaning 10 hours) of running time. I have an idea that you are monitoring it a little too much. Here's what I would do...and it's what your local dealer will do if you take it in...Change the oil, run it...hard, for at least 5 hours without checking the oil. Then look at it and see if you have gained a lot or a little. If its a lot, then take it in to the local guy. I know that's not a great answer or a perfect solution, but that's the way we do it.

 

[AG]

Re: new 5ph 4stroke, gas in oil, what to do?

You may have the following problem.... Do you close the vent on your gas tank? On a warm day, the gas will expand. The gas has nowhere to go except back into the engine and into the crankase.

 

[TOHATSU GURU]

Re: new 5ph 4stroke, gas in oil, what to do?

I never thought about that...but I just checked with one of the techs and he agree's it's a possibility.

 

[JJerry]

Re: new 5ph 4stroke, gas in oil, what to do?

Thanks for replying. The vent on the gas cap is open when running. I will run it for the next 5hrs and check the level to see whats going on. Hopefully all will be well. Thanks again.

 

[TOHATSU GURU]

Re: new 5ph 4stroke, gas in oil, what to do?

AG was pointing out, correctly, that if you leave the fuel line attached to the engine when the engine is not running and the fuel vent is closed, that the fuel might be forced by the built up pressure into the oil. If you disconnect the fuel line each time you run it then that's not the problem.

 

[garyN]

Re: new 5ph 4stroke, gas in oil, what to do?

Why doesn't anyone suggest that this engine has a bad diaphram in the fuel pump. I had it and it ran OK - but pumped a lot of gas in to the engine. Also the dealer never even thought to suggest that - thay wanted to blame me for overfilling it - which I told them was not possible.<br /><br />This engine has a problem that is way beyond the folksey suggestions about leaving the gas line hooked up and "blow by".. Make the dealer remove and check the fuel pump, also you may now have seriously reduced the life of the engine due to diluting the oil. <br /><br />Don't take this lightly - your engine is broken and, even though it runs, it could leave you stranded in a dangerous situation if you use it in the open ocean.<br /><br />Gay N

 

[DJ]

Re: new 5ph 4stroke, gas in oil, what to do?

I would not make any decisions as to whether I had a problem or not until I changed the oil and ran it a while.