Newsletter of the Finger Lakes Chapter, ACBS

Volume 17, Issue 2.................................................................. June 2007

UPDATED june 20th 2007



page -3
















Outboard Motor Carburetor Rebuilding
By FLC & WCCB member Dick Newcomb

Carburetor rebuilding on a typical outboard is not too bad an undertaking especially with a couple of handy helpers. One is a digital camera. Take a zillion pictures as you're removing things to get the carburetor off and as you take it apart. Photographing any disassembly is essential, especially if you've not done it before. Pictures will be invaluable when you go to put things back together, typically days or even weeks later.

The second helper is to invest in one of the Seloc (or other company's) books for that type of motor. They usually are printed by model, for a range of years (such as "prior to 1965" or "1965-1976"), and also by ranges of horsepower (like 3hp-40hp).

Most of these are well-written and take you step-by-step through the disassembly and reassembly processes. They can be a bit like tackling a foreign language when you first start, so it is helpful to enlist the assistance of club members who have done this sort of thing before. Sharing information like this is one of the main reasons our ACBS family exists.

Once you have removed the carburetor, it can usually be opened up by removing five screws that hold the two halves together (see pictures 1 and 2). Slowly crack it open and gently pull the two halves apart. Use a small container like an old cottage-cheese container to hold all the parts. Remember to keep taking those pictures! You will find a cork structure in a ring shape inside. This is the float. It sits inside the bowl where gas enters the carburetor. As gas comes in, it "floats" up and actuates a small needle valve. Once full it is supposed to push that valve up and shut off the gas. Stuck floats can be a major cause of engine trouble: stuck down, they allow the carburetor to flood; stuck up, no gas can get in. The float should be about parallel as you hold the carburetor level. If not, use a small pair of needle-nose pliers and gently bend the brass hinge until it is level.

Examine the general condition of the inside of the carburetor. If everything is nice and clean you may have lucked-out and won't need to tear things apart too much. Here is where an air compressor really helps. If you have one , use the fine air spray tip and blow air through every hole you can find. Take the two jets out. Low or idle speed is typically at the top of the carburetor; high speed is at the bottom. Unscrew them, remove them and look things over (picture 3). A good slow-speed jet is a sharp needle-like point. This is where most problems with idle occur. If the motor runs but won't idle down, bucks, misfires and stalls, it is probably a bad slow-speed needle. If you have any doubt, buy a new one. I've rarely seen a problem with the high-speed jets. They are blunt on the ends. There may be dirt or varnish build up on the needle, but they don't generally go bad.

With the high and low needles out, blow out all the openings. If everything blows through you, may be able to reassemble your carburetor and try it, which is the only way to know if it will function properly
Let's assume the worst. You open up the carburetor and it is a gummy mess! Now you need to remove everything you can take apart (take pictures). You then need to soak all gummed-up pieces in a good carburetor cleaner for several days. (The cleaner is nasty stuff so put it in a closed container.) You also need to invest in a rebuild kit available at NAPA, through a marine supplier, or any of the Outboard Club web sites.
Once you've cleaned all those little parts, rebuild the carburetor with the new gaskets, etc. from the kit. You won't need everything, but the gaskets, float needle and new seals for the needle valves are critical.
Well, put her back together and cross your fingers! Start by turning the needle valves -- low and high -- all the way in. Now open them about 1¼ turns. Try your motor, if it fires and runs in a barrel of water, you're in good shape. But the only way to get it adjusted is out on the lake.
Start with high speed. Open her up and adjust the needle in and out until you get the top end speed, then turn it in just a little. Next, go to idle speed and do the same. Most older outboards (other than the little kickers) weren't super-designed for slow speed. What do you normally do when you take a boat out? Start up, coast a little ways and then open it up once you're in deeper water. Most motors over 25hp aren't idled much.

Well, good luck. I'd be glad to help anyone with their project.
Next time: Coils and points.