mine says it in the smaller engine manual that came with the boat. In the fluid specifications section. Is specifically says "Crankcase Oil (With Filter)"
Buy a gallon container and an extra quart. You may not need that extra quart, but you can keep it on board. I *think* you'll use right around 4 quarts.
New twin 4.3's - 235hp each with Alpha 1 Gen 2 Drives
Mine are 1996 4.3 LX's and use 5 quarts - that puts the level just a hair under the full mark. I have the remote oil filters so that may change my capacity some.