Before Replacing/Re-building the Carburetor

(or... can't fool you twice.)

We often blame the carburetor for: POOR PERFORMANCE and/or a POOR RUNNING ENGINE. Although this does happen, it is not the most likely reason for engine problems. The carb has very few moving and or wear related parts. If a carb has gone bad, it is usually caused by some other reason other than wear and tear.

The following items should be checked before replacing/re-building the carburetor.

Fuel System
1. Adequate fuel pressure at all operating RPM and loads.
2. Dirt in system - Is the fuel filter and/or water separator clear and free flowing?
3. Clogged, pinched, or kinked fuel lines.
4. Clogged fuel tank pickup and/or anti-siphon valve.
5. Water in the fuel.
6. Quality of fuel.

Gasoline is very flammable and highly explosive under certain conditions. 
Service a carburetor only in a well ventilated area away from lighted cigarettes, open flames, or sparks. Use care not to spill fuel.
Clean up any spilled fuel immediately.

Flame Arrestor
1. Is the flame arrestor clean and free flowing?
2. Is the flame arrestor properly sized for the engine?
3. Is it bent or damaged?

1. Does the engine need a tune up? - Points, spark plugs, condenser, plug wires, cap & rotor. 
2. Battery, battery cables, and charging system condition.
3. Electrical connections.
4. Overall condition of cooling system.
5. Cylinder Compression and vacuum leaks.
6. Seizure and/or binding in the drive train?
7. Over or Under sized propeller? In good condition?

1. Is the engine room ventilation clear and properly sized for this engine?
2. Is the boat bottom in good condition.
3. Can water drip onto the engine due to clogged and/or poor drainage?
4. Is there excessive water sloshing around in the bilge?

Protect Your Efforts
Dirt in the fuel system - Dirt is the #1 cause of carburetor failure.
Dirt in the flame arrestor - Air flow is blocked, causing poor performance and/or rough running.
Over tightening when installing.
Clogged, pinched, or kinked fuel lines.
Water entry from fuel tank and/or dripping onto engine from above.

Disconnect batteries.
Shut off fuel supply
Identify, tag, and disconnect all fuel lines, electrical lines, and linkage.
Note carb base gasket condition and type.

Flush fuel lines.
Install a new fuel filter and fuel water separator.
Compare and match the new carb base gasket to the old one.
Clean the flame arrestor and housing.
Service PCV valve if equipped.

Change engine oil and filter if the reason for carb service was flooding.
Check for free movement of throttle linkage.
Ventilate engine compartment.
Connect batteries
Open fuel supply.
Crank engine and then check for leaks.

Check for leaks.
Check choke operation.
Re-check linkage movement.
Bring engine to operating temperature.
Check and adjust idle timing in neutral and in gear. **
Make final mixture adjustments to carb, in gear. **
Lake test unit and verify operation through out RPM range.

** If idle is electronically controlled (such as current Mercruiser, Volvo, Crusader, and other engines), install jumper to disable computer control, before attempting to adjust timing and or idle mixtures.

Note: The above information should only be used in conjunction with your owners and service manuals and should not be your only source for servicing your engine and/or it's carb.

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