"K. Smith" wrote in message
(vii) OK Clams I better reconfirm one of the reasons "your" old Mercs
were so successful was the pistons were small, lots of them but they
were tiny. The surface area of the piston was small compared to the
total length of the rings, it's the rings that transfer the piston heat
over to the very cool bore.

Not only were the bores small, but getting *to* the 99ci illustrated this
point.

IN THE BEGINNING (1962) came the 89.9 ci Merc 1000 with a 2.875" bore. The
next offering was the 93 ci Merc 1100 achieved by boring out the Merc 1000
blocks. This motor with only 1/2 extra ci per hole ran hotter, enough that
it only enjoyed a 2 year production run '66-'67, the risk vs reward was not
worth it for 3ci and 10hp. (today they are rare - and still have that rep as
the hotties of the family)

Going back to the original 89ci block and the drawing board in 1968, they
left the bores alone at 2.875" and instead *stroked* it, to make a
"whopping" 99.9 ci's. And in *that* config it enjoyed a 20 year production
run. Now granted, by the time they got done wringing 150hp out of a little
99ci block, the thing is still a motor that's thermally on the edge, but so
long as the waterpump is working, the advance max's at 21 degrees (23-25
with Cam II) and it don't lean out for any reason, it'll run forever at WOT.
The moral of the story is that the "risk vs reward factor" became much
better by stroking it a lot, than boring it a little.

-W