bertram31.com

The Invention of the Stern Drive

This probably would have had more interest to the fellows on the old 25 board, but since there is a lot of crossover here I thought I put the link up. Anyone who has ever cursed while working on a Merc stern drive (or a Volvo for that matter) will enjoy it.

In the 1960 Miami Nassau race that made the Moppie famous and put Bertram on the map, the only other finisher that day, and second place boat, was a similar deep V design hull around 25 feet long with a stern drive. It was built by Dyer who I am pretty sure built that America's Cup tender that first caught Dick Bertram's eye and inspiered him to hire Ray Hunt to design Moppie. The smaller boat may not have been a Ray Hunt designed hull, but if it wasn't, it was a shameless copy of one.

I have sterndrives on my 26. I have been in absolute awe at how poorly the design has been refined from the early production prototypes to the present day. The internals are very un-service-freindly. Everything is assemble it; measure it; disassemble it; shim it; and reassemble. Some of the proceedures require pressing on bearings, assembling them into the gearcase, measuring, and then disassemble and pull the bearings off to shim them, then re-pressing them. Crazy stuff. Crude. No modern production engineering to speak of. (as in engineering design to make them easier to produce and service reliably)

It is as if Merc was not fully committed to the product or was uncertain of its future and so built the first production run by hand with minimal investment in special tooling or tolerancing. But then they "froze" the design; never doing follow-on engineering to make the parts interchangable or serviceable without fussing and shimming them every time. As if they wanted the stern drives to be impractical to service... so that you would rather buy an outboard.

Maybe that is exactly what they did. And are still doing.

http://www.rbbi.com/folders/pat/isd.htm

What is a real heartbreaker is that BMW started to produce a more modern design, (it may have had issues too, but the design concept is better,) but then Merc bought it from BMW and shelved it instead of refining it.

Peter