OpenTube

Cleaning a Mercury 3.5 hp 4 Stroke Outboard Carburetor

Fixing Boats & Stuff

10,116 views

Struggling with a rough-running Mercury 3.5HP 4-stroke outboard? In this step-by-step DIY guide, we’ll show you how to clean and maintain your Mercury outboard carburetor to restore smooth performance. Whether your engine is sputtering, stalling, or won’t start, a clogged carb is often the culprit. Learn how to disassemble, clean, and reassemble your carburetor with tips to keep your small outboard motor running like new. Perfect for boat owners, anglers, and DIY marine mechanics—save money and avoid costly repairs with this must-watch tutorial!

Please Like, Comment and Subscribe to Fixing Boats & Stuff

#carbuertorclean #outboard #mercurymotor #outboardmotor #boatrepairs #mercury #carburetor

15 Comments

@fixingstuff2647 Creator 1 year ago Pinned

Thanks for watching - I hope you found the video helpful.

@CensorshipGenesis 1 year ago (edited)

Tip: ALWAYS use a decent fuel filter. Specially on these small engines. Be aware there's a small strainer just before the fuel tap. But that thing serve only to arrest Peebles size particles. LOL 🙂
It's dirty cheap and definitely a peace of mind. Preferably a transparent plastic model so it can be easily checked, both for fuel flow and dirt... 🙂Cheers

@birdinthebush 4 months ago

Instead of using a wire brush, I found it easier to use a thread from a bycicle brake cable. They are thin enough to go trough the tiny hole yet thick enough to polish the sides of the hole. Thanks for your help with this ever so common problem in small outboards.

@DavidOlson-u4c 3 months ago

Thanks, very helpful.

@randytricker8585 1 year ago

You had carb issues but everything seems to be clean.

@ronwestfall6030 3 months ago

Instead of the wire brush strands for fine holes, go to a music store and see if they have any broken violin strings or in the worst case buy one. They come in different diameters. They work great.

@robertemberton541 8 months ago

Nice video. very thorough, Many thanks

@DouglasTodd-o8u 1 year ago

very well done and helpful!

@stevebryant9836 1 year ago

Man, I can't wait to get rid of mine. My Yamaha 2.5 works so much better, and is a decade older. I'm currently diagnosing oil in the carb, and have seen others have issues after storing on thier sides, but mine has only been sideways when transporting to and from dinghy to boat. The Merc will run for a while then die while I'm out. The carburetor looks about like yours (2022 motor, square bowl and float) in terms of being clean. I've got a new Suzuki 20 HP on order that I'm stoked about. Less carburetor cleaning in the future when I'm running more questionable fuel in the Caribbean next season!

@vanhkheuamun9407 1 year ago

❤❤

@rossturner8581 4 months ago (edited)

No fuel filter? I've found these engines very sensitive to old fuel I left some in that was only 3 months old and it run terrible I changed it for fresh and it was like a different engine, I now use fresh every time I use it! hope this helps as bad fuel might be the only problem and might save a strip down

@Montenza_M44 6 months ago

u should change it two a 6hp carb next time if u need more power

@glatisant74 1 year ago

Thanks for the vid. My merc 3.5 is 2 yrs old, it started to be unstable so i am carb cleaning to....lol.
Thinking to add a small see thru filter on the gravity fuel line, do you think thats helpful?
Many thanks

@rickwhite4735 3 weeks ago

So I had the same carb same motor and I couldn't blow air or cleaner they the main fuel like hours of picking and soaking I gave up and ordered a 29 dollar carb and it runs mint thing is I could blow air thru the new one either the main line where fuel enters the car.b seems blocked is that normal ?

@rickrick-g9f 6 months ago

I see your mixer needle has a cap on it. EPA snafu? Im down in Mexico and mine has no cap, and i backed it out expecting to see a spring and an O ring, but there was none. The carb rebuild kit shows 2 O rings. 1 for the drain screw and a tiny one for the mixer jet. But the Mercury diagram just shows a spring and the needle and that EPA cap thing. Any thoughts on this? The local outboard guy here says no O ring needed. 🤔