Unscrew the idle mixture screw 1¼ to 1½ turns. (The original Operator's Manual recommends 1¼ turns. The newer version advises 1½ turns.) A screwdriver is needed for this adjustment.
With the gear lever in neutral, close the throttle and adjust the idle speed screw to set the speed to between 1200 and 1300 RPM (At this speed, the engine will tend to 'four-stroke'). Do not let the engine idle at more than 1300 RPM
Put the gear lever into the 'ahead' position. The engine speed should not fall below 1000 RPM
If the engine speed falls below 1000 RPM in 'ahead' at low throttle, adjust the idle speed screw until the engine is running at 1000 RPM
Full Power (Main Jet / High Speed Mixture Screw)
Preliminary Setting of Main Jet
Open the high speed mixture screw 1¼ turns. (This is done by hand, without the need for a screwdriver.)
Final Setting of Main Jet
This must be carried out when the boat is underway. According to the Manual, depending on the type and size of boat, the high speed mixture screw may need to be adjusted either way to obtain maximum speed. Advice from Crinan Marine and the Webmaster's personal experience* suggest that the optimum setting usually lies between ¾ and 1 turn.
* Webmaster's Comment: My Vire 7 powered a Leisure 22, a bilge keeled sailing vessel with a design displacement of 1450 kg.
The magneto contact breaker points gap in a new engine is adjusted at the Factory to its proper value. After 300 running hours it may be necessary to check the gap and possibly readjust it. The following procedure should be adopted:
Remove the starter pulley.
Rotate the crankshaft until the breaker point gap is at maximum.
The breaker point gap should be set to 0.45 mm (0.016 inches) by means of a feeler gauge.
The timing is adjusted at the factory to its proper value to give the greatest efficiency and starting characteristics.
If the magneto statorplate has been removed it must be fitted so that the fixing screws pass centrally through the oval shaped slots. This will ensure the correct timing, provided that the magneto contact breaker points gap is correct.
If rechecking or adjustment of the timing is needed, the following procedure should be adopted:
Check the magneto breaker points gap and adjust it if necessary.
Turn the flywheel clockwise (direction of normal rotation) until the notch on the V-belt pulley indicates the fixing level of the bracket on the left side of the engine (when viewed from the front). The breaker points should just open at this position, which is 30 degrees before top dead centre (BTDC). This corresponds to the position of the piston in the cylinder being 5.8 mm (0.23 inches) BTDC, which can be measured with a depth gauge type timing tool through the spark plug hole.
The only accurate way to check the opening of the points is with a buzzer type continuity tester. If the timing is correct a sound change is noted at this position, 30 degrees BTDC.
If the timing is incorrect, loosen the fixing screws of the stator plate
shift the plates clockwise if the points are opening too early
shift the plates anti-clockwise (counter clockwise) if the points are opening too late
repeat until the timing is correct.
Retighten the fixing screws on the stator plate.
Recheck the magneto breaker points gap and readjust it if necessary.
