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Author Topic:   Gas in my oil
Mississippi posted 09-18-2003 10:58 PM ET (US)   Profile for Mississippi   Send Email to Mississippi  
I purchased a new 2003 30hp 4-stroke Nissan for my 13' Sport. The engine is quiet, smooth and has plenty of power for my purposes. During the break-in period I closely followed Nissan's recommendations regarding RPMs -- basically, take it easy for 10 hours. This was not much of a problem because we mostly use the Whaler in the backwater areas of the upper Mississippi. The one problem I noticed was that the motor seemed a little difficult to start when it was cold, but it always started eventually.

After running about 15 or 20 hours I checked the oil and found that it was completely mixed with gasoline. Oil and gas literally squirted out when I opened the plug! I brought it back to the dealer and he found that the fuel pump was bad. He also called Nissan about the gas in the oil. Nissan told him the problem was caused by the engine not reaching a hot enough temperature to seat the rings. To solve the problem, I am supposed to initially run the motor at 3,500 RPM for 5 or 10 minutes after which I can then cut it back to the slower RPMs we need in backwater areas. The dealer also handles Suzuki 4-strokes and said these motors and other 4-strokes have been having the same problem. I am a bit nervous about having difficulties this soon with the motor and was hoping somebody could offer advice as whether the story I have been told is reasonable.


Jamie 20 outrage posted 09-18-2003 11:38 PM ET (US)     Profile for Jamie 20 outrage  Send Email to Jamie 20 outrage     
I have heard about warming the engine up before using it and I have had bad fuel pumps dump fuel in the oil. And I have heard about putting hotter thermostats in to reduce this problem. Never, have I heard about telling you how to boat and I find that unacceptable. If I were you I would use it how is convenient for you, and if the engine screws up, have them fix it or buy it back, or give you a good trade in. I think 4 strokes have a few years before they get all the bugs out.
JBCornwell posted 09-19-2003 12:21 AM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
This is the first I have heard of this happening in a Tohatsu-made engine, but it has commonly happened to Yamaha made (including Merc) 80 to 115 engines. I did hear of one Suzuki that had it.

Yamaha's diagnosis is the same as the Tohatsu: engine running too cool and therefore over-rich during break-in period. They have recommended getting the engine hot before going into the break-in cycle, and they have also recommended replacing the thermostat with a new 140* T-stat.

I really don't remember why, but I broke the printed rules of break-in on my Suzuki DF70 and ran her up to 5,000 for a few minutes before entering the break-in cycle every time I had her out for the first 20 hours. My wrench may have told me to do that. I had no "making oil" problems.

I think periodic runs at 3/4 or greater throttle for a few minutes during break-in is the solution to seating the rings well and avoiding running under load at below optimum temp.

Red sky at night. . .

jimh posted 09-19-2003 04:59 AM ET (US)     Profile for jimh  Send Email to jimh     
There was some good discussion of this topic in March, 2003. See this older thread:

Also see this discussion on another web site's forum:

(By the way, there are plenty of upset Yamaha owners posting in that thread. Interesting reading, to say the least.)

Apparently, this is a fairly common problem among smaller 4-stroke engines that are run at low speeds.

I guess you can look at it like this: you'll have to change the oil in the sump of your 4-stroke every 50 hours, anyways. What's a little gasoline diluting it gonna harm?

Peter posted 09-19-2003 07:49 AM ET (US)     Profile for Peter  Send Email to Peter     
I have a silly somewhat related question. Can you change the oil on a 4 stroke while its in the water? I think the answer is of more interest to those who would have the big 4-strokes on big boats that are not easy to haul without the aid of a local boat yard.
Barney posted 09-19-2003 08:59 AM ET (US)     Profile for Barney  Send Email to Barney     
Peter, There are pumps that can do it. Drill mounted etc. My 4 stroke manual mentions using a pump as an option. Jim
Bigshot posted 09-19-2003 10:50 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I have heard of the gas/oil issues here but hanging within a circle of about 100 4 stroke engine owners, none have actually experienced it.
Dr T posted 09-19-2003 12:20 PM ET (US)     Profile for Dr T  Send Email to Dr T     
I suspect that the water temperature is a factor. I heard about the problem in Yamahas from a fishing guide while fishing on the Nushugak in SW Alaska last summer. While these engines get run at high speed going up the river, they drift down at idle/low speed. The water was cold enough to have this problem show up.
Barney posted 09-19-2003 07:22 PM ET (US)     Profile for Barney  Send Email to Barney     
I would imagine that the river water is pretty cold. Our gulf water temperature has been 87 degrees up until recently. Jim
jimh posted 09-19-2003 08:07 PM ET (US)     Profile for jimh  Send Email to jimh     
I would caution against buying a cheap drill motor mounted pump. These seldom work well for pumping dirty oil from crankcase sumps.

Our sailing club had one of these to change the oil on our diesel auxillary motor. It would work the first time, but after sitting around for a few months with filthy contaminated oil in the pump, it never worked well again.

I think I ruined about $100 of clothing trying to pump contaminated oil with a cheap, $15, drill-mounted pump. It was a disaster. Better to have paid the marina $75 to do it than to have gotten filthy and ruined all my clothes with that awful cheap drill-motor pump. And that is not including the mess on the drill, the cabin sole, the deck, the containers, etc., that had to be cleaned up.

It has been my experience that changing oil using a pump will require a rather expensive and high quality pump, probably on the order of $200 or more. That is what the mechanics use, and there is a reason for it.

Contaminated oil is nasty stuff, both on your hands and on the hoses, pumps, and containers being used to extract and store it.

Bigshot posted 09-19-2003 10:23 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Actually I use a brass hand pump available anywhere for like $40. I have been using it for years but I do clean it after each use. They are VERY popular among mechanics. Takes me maybe 10-15 minutes to drain 6qts from my 454 using the dipstick hole. If you drop the plug after pumping it, I bet you don't get 2 oz, so they do a good job. Mercedes now does not even have useable drain plugs, cars must be pumped......unless you know a good trick:)
Barney posted 09-20-2003 07:22 AM ET (US)     Profile for Barney  Send Email to Barney     
I agree with you on the drill pump it is nasty. Mine went with the other boat when it sold. I'm sure like Big Shot says there are better ones. There are lots of them in the catalogs. Jim
dgp posted 09-20-2003 04:14 PM ET (US)     Profile for dgp  Send Email to dgp     
The best and cleanest way to do an oil drain on any four stroke engine is removal via the dipstick tube. The Topsider Big Boy vacuum-principle, oil removal device works very well and is normally on sale at one of the boating stores or websites.
I use it on my VW Jetta TDI diesel car, Mercury four stroke, Honda lawn mower and like Bigshot sez it's the approved method on all Mercedes cars.

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