[Water Rat]

gjkailua,

I think it will be tough to get a lot of first hand data due to the limited number of 25' Seafari's out there and the small number of 25' owners on this board. However, I would be very interested in knowing more about your 440 Yanmar/outdrive combo. - as I am thinking about a disel repower for my 1978 23'Sceptre repower. For what it is worth in comparing my boat to yours, and from what research I've done, I would think the 315 diesel i/o (single) would be a good fit. I've got a single 7.4 litre/Bravo 1 (330hp) now, and believe I would get slightly better top-end, much better cruise (speed and efficiency, obviously) with the 315 Yanmar/MerCruiser Bravo 3 package. Benefits comapred the the 440 Yanmar are somewhat smaller block, no need for a separate transmission. Also, look at the Volvo packages (D4 DuoProp at 260hp and D6 Duoprop at 350hp), though these are somewhat heavier than the Merc options. I also have not ruled out twin outboards on a bracket, a la Doodlebug's setup (see pictures in the photo section from the Anclote Key gathering). Also, if it helps, you can see my boat (Chris Downey's 23' Sceptre) in the gallery section here. As far as pwering with what "feels right" for the boat, this is a big concern if mine as well. My boat was originally made (and designed ?) for either single or twin outboard (transom mount), single and twin i/o, and also inboard. The 25' Seafari, to my knowledge, was only offered with single and twin i/o options. I've seen some interesting things, though, including a twin yanmar diesel i/o in a 23' Sceptre (I have pcitures, need to scan and post).
If you wouldn't mind, I would be very interested to learn more of your Yanmar installation. Also, please feel free to ask if I can be of any help. Last, there was a 23' Sceptre owner on here who did put a Yanmar 315/Bravo package in his boat - just can't remember his name right now but will look for it.
Good luck, Chris.