1995 15hp 2stroke merc carb help

boater1234

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Well i just started my new to me 15hp 2stroke merc and low and behold it leaks gas from i believe the primer gasket.It runs really awesome except for that.I looked online and i was thinking about just replacing the whole carb,it seems it's only $209 from a place online and i would know it's all brand new and never been used.Does that price sound about right for a whole brand new carb.I guess all i would need to do is swap them out if this is correct,i have a service manual and i know it comes out pretty easy.I have never took one apart or ever rebuilt one.


Can anyone tell me what comes in a rebuild kit?I believe all i need is to replace all the gaskets and that's it.But i'm not to sure.I know when i pump up the ball and pressure finally hits the carb it seems to leak out gas from that area between the primer gasket and the bowl.When i push down on the primer button and continue to push and push it squirts out gas so i would think that is the only spot but this is my personal outboard and i don't want to screw things up.

I only fig on swapping it the carb out because it's near 20yrs old,so for only $209 as long as it's a complete carb why not.Take a few bolts off,new gasket were the carb goes and bolt back on,can't be to hard,does anyone think i may be going overboard on this and have it checked out to see exactly what it is or just go with a new carb?

I don't think it's anything but the gaskets.But i may as well have my local marina check it out.
 
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Star

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Sep 21, 2010
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Yes, there are some carbs that are hard to fix. In general they are quite simple. You can do this and a carb kit should be about $50. A good carb cleaner is about $20. In most cases they consist of gaskets, a float and needle and O-rings. Some carbs can be cleaned without a kit, but if it uses paper gaskets probably not. Once you do it and succeed you will feel better about the whole thing. If you have never taken apart anything and put it back together, this may not be a good Idea. Pictures are always good as you disassemble it to see where things go. Old gas leaves a flakey residue that plugs up the small jets and passages of the carb, and it must be soaked for many hours to dissolve it. In your case, you just need to find the source of the leak, it may not be too bad, but you may need an o-ring or two. Any good marina should do it for $150. Good luck on your choice for a solution.
 

boater1234

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Most places wanted $150+ and i can get a brand new out of the box carb delivered to my door for only $228,all i have to do is bolt it on and go.That seems like the most logical thing to do,i have taken things apart but for some darn reason i have no confidence in myself to do this and i don't want to screw it up.Taking off the carb and bolting it back on is a breeze.
 

boater1234

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When i push the primer bulb i see gas squirting out of the primer diaphragm on the carb,that is all i see so far,plus were the fuel line hooks into the engine also leaks but only when i push on the bulb when it's hard already.When the engine runs the fuel line and connecter doesn't leak a drop,very odd.
 

boater1234

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Well i took a chance and tried it and man it was so easy,i stressed for no reason.What i found which i hope was the issue was a torn and worn out diaphragm under the primer cover.That is all i can see that was wrong but i just rebuilt the whole carb anyway.

So here is my question,would a worn out slightly torn but very small like pin hole tear cause gas to shoot out of the diaphragm?If yes that was my issue.Overall the carb was spotless inside and out,no gum up,varnish,debris or anything.Mon i'm going to do the impeller and the thermostat as well as the lower unit oil.
 

Star

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I am happy that you took a chance on this one. More people here need to do this! learn about your engine. there are plenty of sources here for all kinds of information. I have a 15hp 4 stroke so I can't help you there. You must get the proper procedure to do the impeller so you don't have to do it two or three times to get it right. When I did mine I had a problem getting the pump output connector lined up with the tube that goes into the head, so I had to remove and reinstall it.
 

boater1234

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ok i need some help with the low speed mixture adjustment.what is the best way to set this mixture?Any help on this please?I have a manual but it has several different ways to do it and i'm a bit confused.Maybe someone can help me on this.Does someone have this motor and has done it before maybe.It seems to run good when i had it going but i don't know if it was set to lean or rich and i have no idea what the last person did to it before i got it.

How would i know if it's running to lean or rich.It says run it a bit richer if i don't know for sure so i'm trying to find out what i may experience whether it's running to lean or rich and i can meet it in the middle.

Any help on this please?
 

Star

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Sorry guy I have been busy. Gently run the air bleeder in till it bottoms. back it off about1 1/2 turns. Start the engine and let it warm up. throttle down slowly until it gets a bit rough. Turn it in until it speeds up and smooth's out. If it gets rougher go the other way. You want to set it on the rich side (more clockwise) If it coughs and spits it is probably too lean.
 

boater1234

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It ran really good before i rebuilt the carb, i hope rebuilding the carb didn't knock anything out of line with the low speed fuel mixture.So here is what i gathered from you and my manual.So i go till it gets a bit of pressure(lightly seated i believe they call it, i guess that's were you start to feel it getting snug,i have never set one of these before but i'm kind of excited to learn all this and my water pump is next today after the carb is all done)) but not to hard in so i don't destroy the needle i gather,then turn out 1 1/2 turns.So i believe out is rich and lean is in.So what i have read is like you said,go all the way in then back out 1 1/2 turns,warm up engine for a few minutes,then it says to turn the screw out by 1/8 turns at a time ,pause 10 seconds in between, then keep doing that till the idle slows down and starts to run really rough,it says mark that spot with some thing,then it says go back in 1/8 turns at a time,pause 10 seconds in between, until the idle picks up and is really rough and misfires,mark that spot and then split the difference between them,it also says to open the throttle from stop to wot really fast to make sure there is no hesitation and sounds clean,it also says in doubt turn the screw a hair bit on the richer side to be safe.


The question i have it while doing all this i don't ever shut down the motor,right?I mean to mark my spots on the carb to know were to lean and rich are.One it starts to miss fire do i shut it down then mark it or keep it running while doing all the marks,i just don't want to harm the motor in a to lean or rich position while i'm making my marks,or the little time it will be running in the idle position while i'm making my marks won't hurt it as long as i don't open up the throttle?

Is this all correct and sound right?

I hope i don't have to worry about any of this when i fire it back up today,maybe it will run as good as before,we will see i guess.
 
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