Below is a compilation of threads regarding standard maintenance parts for the Yanmar 3JH4E (40 hp). Please add to this list as you can.

Al - s/v Persephone
Newburyport, MA

*** Pre-packaged Yanmar spares kits
If you havent already found it, Torreson offers a plastic boxed MINOR PARTS KIT for 3JH4E:

Kit contents includes:
1
119305-35150
Oil Filter
1
129470-55702
FILTER, FUEL
1
129670-42530
IMPELLER
1
25132-003800
V-BELT (A-38)
1
25132-004300
V-BELT
1
726
Water Resistant Parts Box
1
90149
Cooling Treatmemt 12 oz
1
90165
Marine Formula 16 oz
1
X0506590-01
ORING(05-06-590)

Warren Milberg
Herrington Harbour, Chesapeake Bay H28.5

***Belts
While the Torreson link in the first post is a good source of most Yanmar parts (depending on where you live), Ive found that Gates belts (bought at Car Craft and other auto outlets)are far superior to the Mitsubishi belts that Torreson sells and seem to be an OEM product.

john
Portland, Oregon

*** follow up.
A Yanmar V-belt substitute is a Prestone 17435. A possible Oil Filter substitute is a Purolator L14612 and the Yanmar impeller substitute is a Johnson 09-1027B.