How many hours on 400's?

Old 04-30-2017, 07:43 PM
Join Date: Aug 2006
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the lower HP I/O's maybe just as reliable as the new 4 stroke outboards. earlier, high HP 2 stroke outboards, are not so reliable. it is not uncommon to have to rebuild Merc's 2.5 EFI 280 and 300 hp outboards after 80-100hrs. the newer merc 400's now come with an unlimited use 3 yr warranty. i imagine the offshore fishing boat rentals will find out. it is not uncommon for those high use applications to run 800-1000 hrs yearly. some replace their outboards at 2500-3000 hrs.

the highest horsepower inboards last only about 20% of their high horsepower outboard counterparts. the merc 1350 will have to be refreshed at around 200 hrs vs the 400 outboard going over 2000 hrs.

at least part of the outboards longevity is due to lower mass and reciprocating weight. big I/O's are 8+ litre vs 2.6 for the merc 400. other reasons include needle bearing cranks and rods and chrome "nickasil" bores.

there are no inherent reasons that i am aware of that would make a 4 stroke outboard more reliable than a 4 stroke I/O of equal outputs.
bultmand is offline  

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