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I know of Martin but didn't know of the convenience. In the White River around Carendon, Arkansas there were numerous Martins up to 7 1/2 as I recall back in the '50's. They were tough little engines on 14' John boats and never saw one down for any kind of repair and ran one at a good clip especially for a 7 1/2.Fact----Shear pins are a great concept.-----BUT----When motors got bigger in the early 1950's it was impossible to put / pull motor into the boat to change the pin.-----So Carl promoted ----" SHEARPROOF DRIVE "-----And forgot to tell the people that replacing props was more expensive than a pin.------If you are familiar with MARTIN outboards , you would know of a unique feature.-----You tilted motor all the way up.----Operated a pin and the motor could be turned so that powerhead was over the water.-----Prop was over the seat in the boat.-----Easy to change the pin and no chance of dropping parts / tools in the water.