g'day mike,

in the case of b&s they have a mounting hole at each corner of the
engine so to speak. but mower manufacturers only ever drill their
frames to use 3 of those holes, commonly the one under the fuel tank
near the base of the bore , and the other 2 holes at the front or
opossite end of the bore. these holes in the engine are moulded into
the sump of the enging this is very strong so with 3 bolts firmly
fitted there is no way anything untoward could happen.

most mower frames over here are alloy so they are quiet rigid in their
own right maybe some other manufacturers who use steel decks may need
4 bolts to bolster the strength of the deck as in take some
felxibility or wharping potential out of the deck.

but my expereince tells me the engine doesn't need 4 bolts.

len

snipped
--
happy gardening
'it works for me it could work for you,'

"in the end ya' gotta do what ya' gotta do" but consider others and the environment
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