Carb Cleaning

The most common cause of this is the float binding on the pivot pin. These carbs are a real pain to clean properly. I had my 15 hp 4 stroke carb apart 3 times before I got it right. It killed me but I had to buy a can of Berryman's Chemical cleaner at Walmart for $19. After a two hour soak, total flush and reassembly ALL of my problems went away. The only problem I have now is that I have to prop up because I am hitting the revlimiter at WOT.

Carburator flooding

I don't know how to thank you. This is the first response that makes sense and is not a theory. I have new gaskets and needle coming. Once they get here I will report my progress.

Thanks again!

Mercury 4 hp 4 stroke. Good as new

I took your advise. Boiled out the carb, got new intake gaskets and spacer as well as a new needle and bowl gasket. Replaced the fuel in the tank with fresh and changed both filters. Also took all the lines loose and blew them out for good measure. A few pulls with full choke and she fired up and ran like new.

Thank you so much. I was getting ready to order a new carb.

Walt Drechsler

We have had seem a lot of problems with these little Hp engine carbs that the new approach to fixing them is to replace the carb if it doesn't start within a couple of pulls. What it boiled down to was all the time involved with monkeying around with trying to get it running good cost more than just swapping out the carb.

In your case the problem seems strait forward, flooding= stuck float. But it took 3 times to get it to work right. Most times we pull them apart and every thing looks clean and they still get soaked/ sonic cleaned and come back running worst. The problem is corrosion is affecting the machined surfaces and ports. As you have found the needle valve couldn't seat because of the pin, but it probably was because the needle was hanging up in the slide of the seat or the needle sealing surface of the seat is pitted. Other problems seen is it won't idle and everything looks OK inside, but it's corrosion within the idle circuit and with the absence of any adjustment screw the operator can't adjust out the defect.

So once we open a carb we're committed to making the customer happy found that it's a money loosing deal. Throw on a new carb and they start second pull every time. By the way it's not just Mercury this apples to all makes.

Well unfortunately you were correct. I thought I had it fixed but it got me just far enough away from the boat to give me a good workout rowing back! I even did a test run in the barrel for about 10 minutes before I took it down to the marina. My next move will be a new carb. Am I going to have the same issue with the new carb? If so, what can I do to minimize this in the future?

My recommendation is ethanol free fuel. The alcohol is attacking the aluminum. This late in the game you would think Minkuni would try different alloy's to combat the problem, but what the heck they are in the business to sell carbs.