Volvo Penta Marine Products     34-2 10


4.3 GL/GS Gasoline Engines

Resetting Ignition Timing to Eliminate Knock

Volvo Penta has received several reports that 4.3 GL/GS engines running on 87 AKI fuel develop an audible knock on hard acceleration. This audible knock occurs when the ignition timing is set to 6" before top dead center (BTDC). The timing is set at 6" under the assumption that an owner will be using 89 AKI gasoline. Ask the owner if 87 AKI fuel was being used when the knock developed.
To eliminate the knock, you must reset the ignition timing on the 4.3 GL/GS to 1" BTDC (see instructions below.)


Caution: Continued operation of the boat while the engine is knocking may cause internal engine damage.

The timing mark is stamped on the rim of the harmonic balancer. The timing grid is a scale attached to the timing chain cover. It shows Top Dead Center (marked "0") and degrees of advance (before) or retard (after). Each division on the scale represents 2 degrees.

1. Connect a 12-volt timing light to the No. 1 spark plug lead and, following the manufacturer's instructions, use the timing light.

Danger: Do not to puncture the wire or boot, as this would cause a high voltage leak. Make sure that spark plug wires are pushed all the way down into the distributor cap terminals and onto the spark plugs. Nipples must be firmly pushed over the terminals, and boots over the spark plugs. Failure to do so can result in ignition of fuel vapors in engine compartment or bilge, and may result in fire or explosion.

2. Start the engine and let it run until the engine is thoroughly warmed up.


Warning: Have someone at the controls, and keep your hands, hair, and clothing away from rotating parts while you make adjustments to the running engine.

3. Adjust idle speed to specified in-gear RPM, then shift into NEUTRAL.

4. Shut off the engine.

5. Install an adapter plug, Volvo Penta 885163-6, into the distributor and connect the bare lead to a 12 volt engine B+ source.

Note: For more information and instructions, see
service bulletin 34-2, no. 5.

6. Start the engine.

7. Direct the beam of the timing light onto the timing grid.

8. Loosen the distributor clamp, then turn the distributor slowly by hand until the timing mark is set at the appropriate timing figure.

9. Tighten the clamp bolt, then recheck the timing mark. If the timing mark is no longer at the appropriate timing figure, loosen the clamp bolt and reset timing according to the steps listed above.

11. Stop the engine.

12. Remove the adapter plug.

Note: The Engine Components volume of your Volvo Penta workshop manual set(s) lists timing and fuel requirements in the Tune-Up Specifications section.


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