I had an Eberspacher D4 fitted to my 2001 Bavaria 40 (not Ocean) a couple of years ago. It is fitted in the lazarette. The unit struggled to get hot air to the forward cabin, probably due to the long run of ducting from stern to bow, so I only have two outlets in use now – one in the saloon and one in a stern cabin. The air ouput is now very hot, so I could probably use another outlet or two in the saloon and/or the other stern cabin.
For my/our size of boat, I think the Eberspacher website recommends a D5. However that takes quite a bit more power than the D4, which I wasn’t keen on.
For the air inlet, the fitter originally used one of the air vents below the helmsmans seat at the stern, but this wasn’t adequate. He had to drill a larger inlet hole beside it. Alan’s idea of an internal air inlet sounds like a good idea, if that would give sufficient air input.
I have a couple of tips:
1. I wrapped all my ducting in Thermawrap insulation. This was partly to reduce heat loss, but also partly because the ducting gets really hot.
2. My exhaust outlet is on the transom. With my dinghy on the stern, I was getting splashback into this when heeled over in a big sea, causing the exhaust pipe to become blocked. If you have a good size loop on your exhaust pipe you’ll be ok, but mine wasn’t fitted with a big enough loop to stop water getting past it. I fitted a stainless steel clam shell vent/cowl over the exhaust outlet and all has been fine since. Your Ocean transom is probably higher than mine of course.