Vire 12

The Vire 12 is the more powerful "big brother" of the Vire 7. They share many features and components. However, the compression is higher in the Vire 12 (9:1 versus 6.5:1) and the inlet and exhaust ports are cut differently, allowing the Vire 12 to rev much faster (4500 versus 3200). The higher maximum revs in turn require a bigger reduction gear (2.7:1 versus 2:1), in order to maintain the same maximum propellor speed.

In terms of outward appearance, the most obvious difference is in the location of the spark plug: on the Vire 7, the spark plug is set in the after side of the cylinder block; on the Vire 12, the plug is on the for'ard side. In terms of construction, the Vire 12 actually has a different carburettor, a different cylinder block, and a slightly different exhaust gas collector / silencer.

The Vire 12 was first made by Valmet in 1981, but I don't know for how long it was made. Manufacture of the Vire 7 ceased in April 2002, but manufacture of the Vire 12 had stopped several years earlier and spare parts are now difficult to obtain.

An article about the Vire 12 was published in the Finnish boating magazine "Vene" in 1981. Click here for an English translation. If you want the original Finnish article, there's a poor-quality image here (page 1) and here (page 2).

Vire 7 (note plug pointing to rear) Vire 12 (note plug pointing forward)
Model Vire 7 Vire 12
Type Two-stroke, watercooled, piston ported Two-stroke, watercooled, piston ported
Power KW (HP) @ RPM (at propellor shaft) 5.1 KW (7 HP) @ 3200 RPM 8.8 KW (12 HP) @ 4500 RPM
Displacement 269 cc 269 cc
Stroke 70 mm 70 mm
Compression Ratio 6.5:1 9:1
Carburettor Tillotson Diaphragm Type Bing Fuel Bowl Type
Fuel Pump Diaphragm Type Diaphragm Type
Fuel Petrol:Oil 50:1 (2%) Petrol:Oil 50:1 (2%)
Fuel Consumption 2.5 - 3 litres/hour 3.5 - 4 litres/hour
Ignition System Flywheel Magneto Flywheel Magneto
Primary Starting System Combined Starter - Generator Combined Starter - Generator
Secondary Starting System Hand Hand
Cooling System Raw Water Cooling Raw Water Cooling
Forward Reduction Gear 2:1 2.7:1
Reverse Reduction Gear 2.5:1 2.5:1
Weight (Manual Start) 55 kg
Weight (Electric Start) 65 kg 66 kg

Turning a Vire 7 into a Vire 12 is a major undertaking, involving resculpting the block and regearing to accommodate the higher peak revs. However, there is a way of simply increasing the torque of your Vire 7 at lower revs. That is still quite a big undertaking, but at least one owner has found it to be worthwhile.

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