Thought I would share something I learned years ago when rebuilding outboard carbs.
As we all work on our fuel system MBA`s there are some things that can make the chore less expensive and easier to do.
1) Don`t buy complete rebuild kits for the carbs. They contain lots of parts that you dont need. Exampes are throttle return springs, throttle butterfly and bowl screws and other assorted parts that never wear out.
2) Instead, buy the repair gasket sets and float needles separately. Double check to make sure that the gasket sets include the carb to intake manifold gaskets, if not, order those separately. The savings can be dramatic. The complete rebuild kits for my Mercs run about $35 ea. The alternative is about $10 ea.
3) Outboard carbs are very simple to work on. Normally you can unbolt them as an assembly after disconnecting the airbox and the fuel and bleed hoses. Lay them on the bench and pop off the connecting linkage and contoured fuel lines and lay them off to the side in the orientation they came off. Take pictures when in doubt.
4) I like using surgical towelettes that have a plastic film on one side. Mark each towel with the respective carb number 1 ,2, 3 etc. Only work on one carb at a time. Remove the bowl and high speed drain plug, before removing the float pin, invert the carb body with the float up and check the float height and note the measurment, measured with a scale from the carb casting (without the gasket) to the highest point of the float. Pull the float pin and take off the float and drop the needle, sometimes they are held on the float arm with a little clip. Some needle seats are removable, some are not. usually made of brass with a screw driver slot and gasket underneath. Remove the low speed jet from the upper carb body. First, screw in the jet until it lightly seats in the casting and take note of how many turns in it took to seat. This will be the intial setting after reassembly. If the screws have been tampered with previously the usual base setting is 1 1/4-1 1/2 turns out.
5) Remove all remaining gaskets and you are ready for the soak. Do not remove the fixed high speed jet from the bowl, they take a special jet removal tool and a standard screw driver will damage the casting and threads.
6) From the auto parts store, buy a gallon of commercial carb cleaner. It has a basket for the parts inside. It is a mild acid and cleaner that will remove all the varnish and gum from the carb. For severly varnished carbs, an hour soak will usually do it. Occasionlly lift the basket of parts and lightly agitate up and down. You will see the varnish lifting off the parts. The solvent will not harm the plastic connector linkage left on the assembly so dont worry about it.
7)Wash the parts out with a garden hose and shoot the water through all the openings and passages. Then compressed air blow dry. Watch the solvent in your eyes and mouth when doing this!
8) Reassemble the carbs with the new parts, check the float height after installing the new float needle and cross pin and adjust by bending the metal float arm if needed. I rarely have to adjust the float height unless someone else has been in there tinkering around.
9) Cleanliness is very critical, make sure that the mounting surfaces of the carbs and engine intake are spotless with no old gasket material left behind. I like to use a straight razor and gently scrape the surfaces and avoid gouging the aluminum surfaces. Reassemble the connecting linkage (it will snap back together) and fuel lines between the carbs and secure with new cable ties or hose clamps as needed. Now you have the assembly to bolt back on the engine as it came off.
10) Bolt everything up, make sure the fuel is clean and a new inline filter is used before priming her up. Check for leaks and respond accordingly. The best way to adjust idle speed and mixture is too tie the boat off at a dock in the water and make adjustments in the real world environment with the proper back pressure in forward gear with the engine warmed up and running. If the engine wont start or stay running, back out the low speed mixture adjustment screws an 1/8 of a turn at a time to richen the idle mixture until it stay`s running.
11) It is best to have the correct service manual for setting idle speed, idle timing and mixture balance.
This can be $400+ job at a dealer and you can do this yourself for about $100. This is not "rocket surgery" and from what I`ve seen on this site, most of you guy`s can do this easily.
fitz73222
