1996 9.9 4 Stroke: Gas in Oil

[FordF100]

Purchased boat with 1996 4 Stroke 9.9. Engine ran fine for 20-30 minutes then seemed to overload, overheat or something but would die. When trying to start it (pull rope) seemed like it was flooded but it may have overheated, not certain. Replaced plugs, installed new impeller and changed to a non alcohol type fuel. Then it ran great during two separate outings. We used it for trolling only. Went to change out the oil and when I pulled the stick out it oil flowed out and smelled strongly of gas. In discussion with local mechanic he said the gas in oil was a problem with 4 stroke when used for trolling only. After reading common questions on this site water in oil seems to be what is common because these engines don't get hot enough. The oil I took out smelled strongly of fuel and seemed very fluid as if very deluted by fule. The local mechanic said I just needed to change oil possibly after every outing. What are possible resolutions if there are some? Thanks, Jerry

 

[tx1961whaler]

Re: 1996 9.9 4 Stroke: Gas in Oil

It's in this post:
http://forums.iboats.com/showthread.php?t=158085

 

[FordF100]

Re: 1996 9.9 4 Stroke: Gas in Oil

Yes I know I read the thread. It just seems there is too much gas in the oil so I'm suspecting more to the issue then what is mentioned in the article. I'm looking for further guidance on making sure it isn't. If anybody can provide some guidance that would be great.

Thanks,
Jerry

 

[Silvertip]

Re: 1996 9.9 4 Stroke: Gas in Oil

I am not familiar with this engine but will assume it is carbureted. As such, the carb may need rebuilding or at least inspection to make sure the float level isn't set too high or that the inlet needle and seat are functioning properly. If this were my engine, I would change oil and filter, run the boat at moderate speed for a mile or two and then change the oil again. Now run the boat at speeds above half throttle, preferably near wide open for several miles. In other words, run the "be jeepers" out of it. Head back to the dock and immediately check the oil. If there is again evidence of fuel you have a fuel pump or carburetion issue. When out trolling, you need to run the engine at faster speeds periodically, especially on the way back to the dock to burn off the excess fuel. If this is a serious problem (meaning the oil level rises significantly after even a short fishing session) this engine needs help. Continuing to run it with fuel diluted oil will damage the bearings as they are not being lubricated properly. (They will however be very clean!)

 

[boobie]

Re: 1996 9.9 4 Stroke: Gas in Oil

Could be you have a cold running mtr, bad thermostst, or a leaking fuel pump diaphram.

 

[ondarvr]

Re: 1996 9.9 4 Stroke: Gas in Oil

I think there is a sticky on this.

4 strokes that are used for trolling frequently contaminate the oil with gas and once the oil is in there the motors are rarely run hard enough for it to evaporate quickly. Installing a higher temp thermostat can help.

 

[Jim311]

Re: 1996 9.9 4 Stroke: Gas in Oil

Bad rings can lead to this as well, but if I were you I'd just check the oil frequently and change it frequently.

 

[JB]

Re: 1996 9.9 4 Stroke: Gas in Oil

I had a 1997 9.9 Johnny 4 stroke. Pretty much the same as the '96. I followed my firm rule. . .I bought a Factory Service Manual.

It has been a few years since I sold her, but I do recall that the mixture control sensors were pretty complex and involved temperature and vacuum sensing and mixture changing. I think more than one of them had the potential to leak fuel directly into the crankcase if ruptured or worn.

You need a factory Service Manual. That is not a Plain Jane fuel system.