Well it happens to be one of the longest manufactured basically unchanged 2 stroke outboards from late 1970’s to mid 1990’s. It’s a Yamaha outboard that was also sold as a mariner. It’s 2 cylinders, twin carb, steel crank, 36 cubic inch, 2 to 1 gearcase that all the smaller mercury cleavers fit, it came as both a short shaft and long shaft, tiller and remote control models, manual and electric start models, weighs about 150 lbs, was available with factory Yamaha power trim with Pro 50 brackets, it had between 140 to 150 compression, it is sometimes referred to as a commercial model, other than color changes the other real difference in models was the later oil injection
Here is a ugly looking one but this one shows the Pro 50 style clamp bracket that came on the models with power trim.
https://www.facebook.com/marketplace/it ... _type=postFor a 40 hp they are strong...like all twins they sound a bit rough running at low speed. But you can really improve the performance for a light boat application with reeds, minor port clean up and blueprinting.
How do I know? Because I built one in 1996 to race in Sports C after the rule change in early 1995 to increase the displacement from 35 cubic inch to 40 cubic inch to allow the new 40 hp twin mercury to race in the class. The Yamaha triple, the tohatsu and Nissan twins were all 31-32 cubic inch. The big advantage for the mercury was the off the dock start. By the time the Nationals came around in 1995 many racers with the smaller motors quit. Our tohatsu was the only non mercury in the Nationals race. I never got the chance to run the Yamaha because the Sport C died after 1995.
Rather than play with a 25 hp or 30 hp twin. I think these motors are an equal cost option with far more upside. Because of the two piece block...the 40 hp mercury 40 cubic inch twin would be a more costly build. I know of a few of the 40 mercury motors that did race in 1995 that were later modified with good performance improvement. Kevin F was one.
