jaguartx,

Fwiw, in 2006 I bid on/bought for a grade-school chum (who is a commercial trotliner) a pair of 1965 40HP JOHNSON outboard motors at an auction.
(He needed 2 more outboards for his ever-increasing fishing business.)

About 6 weeks ago, I talked by phone to Bob & he said that both of those OBs are still running FINE, with no more than normal maintenance procedures.
(He runs his trotline boats 365 days a year.)

I'd bet that he runs each of his outboards more in a single year than recreational boaters do in their lifetime. Further, my guess that his 1957-65 OMC Big Twins will be running acceptably long after recreational boaters have had to replace their "modern" outboards. = Big Twins are grossly "over-engineered" & "tougher than a dollar steak".

yours, tex

"VICTORY OR DEATH"

William Barrett Travis, Lt.Col., comdt.
Fortress of The Alamo, Bejar
F'by 24, 1836