How To Clean Carburetor On Mercury Outboard

Have been reading up on cleaning the carb on a 3.3 however I just wondered if any issues to be aware of before I remove ? Any kit needed to reassemble for instance once have cleaned . I have viewed various you tube vids but just thought I should be prepared and consult collected forumites wisdom . I think the last time I touched a carburettor was on an MG so rather rusty on topic and I feel I should learn about.

I have a few books but are there any 1 day outboard servicing courses on south coast which might assist any one can recommend where you can practice?

VicS

Well-known member

Joined: 13 Jul 2002

Messages: 46,456

Have been reading up on cleaning the carb on a 3.3 however I just wondered if any issues to be aware of before I remove ? Any kit needed to reassemble for instance once have cleaned . I have viewed various you tube vids but just thought I should be prepared and consult collected forumites wisdom . I think the last time I touched a carburettor was on an MG so rather rusty on topic and I feel I should learn about.

I have a few books but are there any 1 day outboard servicing courses on south coast which might assist any one can recommend where you can practice?

Pretty basic ... only the one jet to clean I think

Remove the bowl carefully with a view to reusing the gasket

Check the operation of the float valve.

I don't think you'd need a 1 day course to learn how to clean that one ........ 10 mins would be generous

Just watch the float pin doesn't slide out and roll somewhere never to be seen again.

Not much to go wrong though.

With the bowl off stand the OB upright and turn the fuel tap to on to check you have fuel flow. It is not unknown for the tap to get blocked.

Remove the main jet and blow through it and the passage. Look for the small hole that is the slow running system and blow through.

If you have let fuel dry out in the carb expect to have clean it out at least twice before you get all the gunge out.

jwilson

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Joined: 22 Jul 2006

Messages: 5,499

Once you have the float and float needle back in, try tipping the carb upside down and with a bit of pipe attached to the fuel inlet spigot try sucking and blowing through the pipe. If you can create a vacuum in the pipe and it holds against the tip of your tongue then you have a good needle seal. You might be able to blow through it if you have powerful lungs and it's a very light float but often the seal is so good (or should be) that you won't be able to blow through it either.

In my experience getting this seal to be 100% is one of the biggest problems with small carbs. If you can't hold a vacuum either the tip of the needle is damaged or the valve seat is scored. On bigger carbs I have sometimes been able to dress both of these with very fine emery paper but on tiny carbs it's usually best to just buy new parts.

Richard

Thank you to all for advice . Will give this a try but it's not so much the cleaning as subsequent reassembly that seems to be the challenge .

Easy job

Worth sourcing a screwdriver with at least an 7 inch shaft

Don't lose the pin for the float.

Spyro

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Joined: 18 Jan 2003

Messages: 7,585

Location: Clyde

First time I did mine i actuallt removed the crab first but then discovered it's not necessary. Just turn it upside down and remove the float bowl, a good clean out is usually all thats needed to get it going again

Thanks Spyro that seems the way to start and hopefully avoid further hassle . It was serviced professionally not so long ago so worked then so it might be as simple as you say.

Spyro

Well-known member

Joined: 18 Jan 2003

Messages: 7,585

Location: Clyde

Thanks Spyro that seems the way to start and hopefully avoid further hassle . It was serviced professionally not so long ago so worked then so it might be as simple as you say.

As others say just be careful with that little needle. With the whole lot upside down when you take the bowl off it should stay in place.

VicS

Well-known member

Joined: 13 Jul 2002

Messages: 46,456

All good advice here and be not afeared. Like you I hadn't touched a carb since my A series days but I took mine apart (2.2, same carb AFAIK) & rinsed it out without too much thought... The whole carb thing came back to me as I was doing it.
Engine runs fine (had been dormant for 20+ years) but carb clean was precautionary not a diagnosed problem.
You'll be fine.