The French generally do not adopt words from other languages.
Then again, Week-End is not the way it would be spelled out
in American English. I do not know how UK or Commonwealth English
treats the words. In any case Weekend is a concept well accepted
in USA. Borrowing phrase to promote as a brand for outboard motors as leisure time and a luxury consumer good life style seems a good plan.
Is there anything to be learned from magneto or carburetor? In USA
practice carburetors and magnetos were source from vendors and
usually marked with brand, model and in case of magnetos serial
number.
My guess, based on looks, is that the motor has a UK connection,
Louis