Gas in crankcase oil pro 9.9 kicker .

[008wagon]

My 9.9 merc pro kicker is getting gas in the oil . I use this to slow troll a lot but always give it 5 minutes of full throttle at the end of the day clean it out . Oil smells like gas and is rising . Any idea what is causing this ? Serial number is OR460451 . Thanks

[EuropeanAM]

Either the carb needle is sticking open, or the fuel pump diaphragm has ruptured.

Will need to determine WHICH is the case, correct, and change engine oil before running again. Good idea to disconnect the fuel from the engine until it's addressed.

Moving your thread to the 4-stroke forum for you.

[008wagon]

Thanks for the help . The oil is very black and smells somewhat of fuel but somewhat not . I removed the thermostat and it is pretty crusty and looks like it could be partly stuck open . Would this cause this issue not fully warming up ? I remember last fall I had to keep it at half throttle for 5-10 minutes before it would stay running in 45 degree water and 30 degree air temp . That seemed strange. Other wise it runs totally flawless. Would a fuel pump or carb issue show it self in running issues also or not ? Thanks

[620Ranger]

Don has your answers for fuel in the oil. The engine not coming up to temperature can cause condensation to add water to the oil. As a cold weather troller, my pro kicker makes some oil, due to condensation, with cold temperatures. I have dealt with everything brought up in this post with various Mercury kicker motors, fuel pump diaphragm, carb needle not sealing and thermostat replacement. It’s my opinion that the Mercury kickers are very temperature sensitive, when it’s real cold I need to high idle the motors for awhile and then they will slow troll fine. If you think it’s fuel, start with Dons suggestions, if you think it’s condensation, change the thermostat. Like Don says, change the oil before you run it again.

[008wagon]

If the thermostat was stuck open wouldn’t it cause a incomplete burn and let fuel wash past the piston rings ? I’m just curious what you guys think . Fuel pump is my next idea but wouldn’t that fill the crankcase up fairly quick and cause running issues ?

[SilverFox579]

Your crusty thermostat could BE the problem and, if this were my engine, I'd replace the thermostat before doing anything else. If engine doesn't reach normal operating temp it will "make oil", it will smell like fuel, and will contribute to accelerated engine wear due to internal parts not coming to temp.

I'm also a cold weather troller and spend many, many hours trolling in 38° - 45° degree water. Not sure if your 9.9 is same, so FWIW, my 8hp has over 450hrs and here's what I do - move to throttle only, crack open, close choke, pump primer bulb 3 or 4 times, then hit starter button. Always starts instantly, then I let it "high idle" a couple minutes while I get gear ready to deploy, push choke in, throttle down, put in gear, and I'm away.

[008wagon]

Really hoping it’s the thermostat. It’s really crusty and don’t look like it has been working . The stem of it is full of stuff .

[SilverFox579]

Replace thermostat and change engine oil. Try to run mine WOT 10mins after a several hour trolling session, takes me 5 - 10mins to stow gear and hose deck off so wife takes helm while I play deckhand.

[008wagon]

New thermostat. Still making oil . Thinking fuel pump now. if it was the carb wouldn’t I have running issues ?

[SilverFox579]

Check fuel pump diaphragm as Don suggested.

[EuropeanAM]

Could be either... might not necessarily notice a needle that leaks only under specific conditions.

One other potential cause: Connecting engine to a Pressurized Fuel System, WITHOUT a Fuel Demand Valve in place.

Are you using the 3 gallon portable tank and line that CAME WITH the engine, or some other fuel source?

Does the CAP on the tank "click" when you tighten it snugly? If so, is there a Fuel Demand Valve (FDV) in the fuel line?

[008wagon]

Could be either... might not necessarily notice a needle that leaks only under specific conditions.

One other potential cause: Connecting engine to a Pressurized Fuel System, WITHOUT a Fuel Demand Valve in place.

Are you using the 3 gallon portable tank and line that CAME WITH the engine, or some other fuel source?

Does the CAP on the tank "click" when you tighten it snugly? If so, is there a Fuel Demand Valve (FDV) in the fuel line?

It is connected by a t fitting to the main gas tank in my boat . The other motor is a 175 pro xs 2 stroke . It’s been plumbed like that for 8 years . There’s no valves to turn at all on it

[620Ranger]

Check fuel pump diaphragm as Don suggested.

This, is what I would check next.

[008wagon]

Is there anyway to test the fuel pump or just disassemble it ?

[620Ranger]

Disassemble it, when you take it apart if the diaphragm is torn you will have gas entering the crankcase.

[SilverFox579]

I would just get a diaphragm kit and replace the old one, have thing about those whether automotive or marine, and don't reuse any that can be easily and economically replaced.

EDIT: Guess I eat my words on that one, that little kit (same one for your 9.9 and my 8) is pricey.

[008wagon]

Ok I got a question. I shift my motor into reverse at full throttle to keep the prop from spinning when going down the road . Anyway this would cause this problem?

[008wagon]

Ok I got a question. I shift my motor into reverse at full throttle to keep the prop from spinning when going down the road . Anyway this would cause this problem?

or is it possible that running mercury premium plus at 150 to 1 in my tank would cause issues also . I always use Quickleen with it also . Thanks

[008wagon]

I run the premium plus for my optimax

[EuropeanAM]

Ok I got a question. I shift my motor into reverse at full throttle to keep the prop from spinning when going down the road . Anyway this would cause this problem?

As long as what you meant to say is that you place the CONTROL LEVER into REVERSE with the ENGINE OFF, then no, this is not causing the problem. Note that the engine should NOT be shifted unless it is RUNNING, or the prop is SPINNING.

150:1 Question: MAYBE, over a long period of idling (not seen enough testing to confirm or deny this one). Theoretically... the 150:1 is for ONLY Optimax models (not for 4-strokes).