The Boating Forum - Mercury Outboard Leaks Gas when Trimmed Up

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Key West
04-28-2004, 12:08 PM
I have just taken delivery of a Key West 1720CC with a 90HP Mercury Outboard. When I trim the motor up and out of the water (with the engine off), a gas/oil mix drips out of the engine and into the transom of the boat.

I took it back to the dealer and they say it is a common problem on this engine because when the motor is trimmed up, a float rolls up and allows the gas from the carborator to flow out. They called Mercury and they say there is no fix for it.

Is this anything others have experienced? Does it get better or worse over time? I have only run the engine about 2 hour thus far and it seems to let a considerable amount of gas come out. I am planning on taking a can or something and try to determine the exact amount that comes out. It does eventually stop. It makes a mess in the transom and obviously finds its way out the drains and into the water causing a noticeable slick.

This boat will be used for transportation back and fourth to our island cottage, so it will stay in the water most of the summer, so the need to trim the engine up and out of the water is obvious so I avoid corrosion. I do plan on getting a lift for the boat eventually, but this is still a hassle.

Anyone have any ideas? Thanks!

04-28-2004, 12:45 PM
Is it a 2 stroke carb. engine. I have owned a Rude, My dad has a Yammi, and now I have a 95 Merc 225 they are all 2 stroke with carbs and they all dump a little fuel oil mix when trimmed up all the way. they also all smoke a little which is a good thing I know she is getting oil. I will have to say that the Merc dumps the most. It does make a mess but I wash it down after every trip and I am used to it! Hope this helps> ;cool; ;cool;

iron banks
04-28-2004, 12:46 PM
I have had two different mercurys in the past two years. Neither one of them did this. Forget the dealer and call mercury yourself. Tell them that this is quite a hazard and that you want it fixed. I would not be satisfied with your current situation.

04-28-2004, 01:50 PM
all my mercs have always dumped a little out
try not to trim up so far

04-28-2004, 06:20 PM
This will reduce the problem to just the fuel in the bowls. As pressure builds in the tank it will force more gas into the system and then overflow through the main jet and out the carb throat. After your trips are finished and you disconnect the fuel hookup you could also bleed the fuel line into a cup.

You could also try stuffing a "Bilge Buddy" absorbant pad in front of the cowling. NAPA carries these.

Good luck!

04-28-2004, 08:28 PM
My 1994 Evinrude did this when trimmed all the way up, so I didn't do it anymore. Trimmed 1/2 way up max worked fine for me for 9 years. That motor always ran great but was picky about how it was trimmed. It could not be started if it was trimmed all the way down (flooded). If it was trimmed up a little, all you had to do when warm was bump the key and she fired right up. Fuel injection eliminates so many differant problems.

04-29-2004, 12:26 AM
This is another reason why I like fuel injection so much better than carburetors. Carbs are ancient technology which was never intended to be tipped to any extreme. Unfortunately, we need to tilt our outboards now and then, and the gasoline will pour out when we do it too far. The only way I know to fix it would be to figure out a way to defy gravity.

04-29-2004, 12:37 AM
I have the 90hp ELPTO model ( 2 stroke ) 2003 model . Yes it does lose a bit of gas /oil when tilted right up .
The saleman told me it's quite normal ( told me this before I bought the rig home ) .
I'll be interest in how much is leaking out from your engine . I guess mine leaks about 0.25 of a cup ( but I only tilt as far as the manaul outboard transportation level can be engaged )

Reel Life
04-29-2004, 07:41 AM
Disconnect the fuel line from the engine and run the engine out of fuel before triming the motor up. No more leaking will occur.

04-29-2004, 07:58 AM
I think people that read this might think that these motors are leaking out gallons of gas but this is not the case. My Merc might dump less than one ounce of gas-oil mix. I do agree that carbs were not made to be tilted 90 deg from the norm but to trailer most boats you must tilt the motor. I have removed the fuel supply in the past but a little soap and water will clean up the problem. :grin: :grin:

04-29-2004, 09:07 AM
I know about all the gas leaking out of an 1972 50 hp merc. The gas would evaporate, leave the oil which would collect the dust, what a mess. Always cleaning up. A friend of mine said turn the motor all the way to the left, (you know like making a hard right turn) and it won't do that. Sure enough it worked. I don't know if the new motors are the same but you might give it a try. The gas did not drip out of the carbs in that position.

Hope this helps!

04-29-2004, 04:44 PM
My previous boat had a 115 merc ob. When trimmed all the way forward, I too experienced leakage. It was coming from the oil resevoir tank mounted to the engine. I started only filling the tank to the 1/2 full mark, so that when trimmed up, the oil wasn't all against the cap of the tank. In my case, I could go out all day and not run through that much oil, so I wasn't at risk of running out. I still kept some oil onboard just in case. That fixed my problem.

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