F15 - Making Oil - Fuel Pump Diapharagm?

[haydensimons]

Hi,
New to the forum. I have an Yamaha F15 that is "making oil". At one point, it looked like oil and gas was coming out of the air intake that I believe draws air into the carb. It wouldn't run over about 5 minutes without "choking" out.

When I saw the oil come out of the air intake, I thought to check the oil to see how low it was. To my surprise, it was to the top of the dipstick and smelled like fuel.

I drained all of the oil out and filled it back up. After that, I ran at varying RPM's for about an hour. It ran fine, but the oil level did increase a little and it smells like fuel again.

After looking online, it appears that a bad fuel pump diagram could be the culprit. I have a manual for this motor and see that there are actually 2 diaphragms in the fuel pump. One is round, the other is more square shaped. Which one would cause the issue? The more square shaped one (the one that you get to after removing the four outer screws from the fuel pump) isn't very pliable. It seems to have more the consitency of vinyl than rubber. Is that how it should be?

Any help is appreciated.
Hayden

 

[99yam40]

Re: F15 - Making Oil - Fuel Pump Diapharagm?

replace them both or tear it apart and see what needs replacing, or replace the whole fuel pump and hope that was the problem

 

[haydensimons]

Re: F15 - Making Oil - Fuel Pump Diapharagm?

Thanks! I would take it to someone, but unfortunately, there's only one certified repair shop within an hour of me and they are closed until the middle of next week.

Where could I order parts for this? And any feedback on how flexible the diaphragm should be?

 

[99yam40]

Re: F15 - Making Oil - Fuel Pump Diapharagm?

lots of places to order parts on line if you look.
This site sells aftermarket parts and maybe Yamaha ones too
http://www.iboats.com/Yamaha-Outboa...4271280--**********.699329018--view_id.268703

You never posted your model # or year so you can look up the part # needed here http://www.boats.net/parts/search/Yamaha/Outboard/parts.html

 

[haydensimons]

Re: F15 - Making Oil - Fuel Pump Diapharagm?

Thanks, Yam! I'd called myself looking for sites that sold parts, but I guess I didn't look hard enough.

It is a 2002 F15 ESHA. The fact that gas/oil was coming out of the air intake has now got me questioning whether it is the fuel pump...maybe the carb is the issue?

 

[Silvertip]

Re: F15 - Making Oil - Fuel Pump Diapharagm?

Oil on a four stroke does not pass through the carburetors so the carb is not the problem. Leaking fuel pump diaphrams can pump fuel directly into the crankcase which is where the oil lives in a four stroke. Here are things that generally cause making oil in a four stroke motor: Wrong prop meaning the engine is lugging, long extended periods of trolling/idling, a bad fuel pump, or an engine that does not get hot enough (running too cool). You apparently do not check engine oil very regularly so it is very possible you have shortened the life of this engine running it with oil heavily diluted with gasoline. Gas is not a good lubricant so engine bearings suffer. Check engine oil before every trip so you know before leaving the dock whether or not there is a problem.

 

[99yam40]

Re: F15 - Making Oil - Fuel Pump Diapharagm?

never looked at that motor but I feel it would have a crankcase vent like automotive PCV leading to air box that the over fill could get through.
Just a thought