I just posted a For Sale notice for an A4 that is a long sad story. Feel free to read it. Regarding this thread, I chose to replace my aborted attempt at installing a used A4 with a new Mercury Bigfoot Sailpower 4-stroke 9.9hp outboard. I've had experience with both motors and can offer these observations:
1) the A4 and E27 are designed for each other and are a perfect match of power, economy, and utility - all good in a sailing vessel.
2) the E27 design has an unfortunate tendency to uncomfortable prop walk with any inboard, except possibly the diesel/saildrive combo mentioned earlier, that is impossible to remove given the specific design engineering of the vessel.
3) the E27 is wonderfully designed to accommodate an outboard in the transom cutout engineered for that purpose - prop behind the rudder removes the prop walk and dubious reversing problems.
4) electrical and charging systems are better handled by an inboard of any make or model.
5) there is no way to amortize any installation of a new or used inboard in todays market for E27's - but an inboard is generally meant for the long haul.
In other words, both systems work well at solving different sets of criteria so you will have to make your own choice. I chose the outboard instead of a new/used A4 or BetaMarine10 (which comes with A4 mounting options- bolt and go) based on the criteria important to me - cost, reversing reliably and quickly, and I can go to the head while one of my 9 or 11-year-old sons take the tiller briefly in safe conditions. I, also, would only go back to an inboard if it were a saildrive with whatever motor - gas or diesel. But that's sort of like putting an outboard under cover, isn't it. I'm real happy with the transom mount as I don't have to lift, I just tilt and everythings out of the water - and it's a whole lot easier to service NOT on a bracket.
I've really got to work on this TMI syndrome, harder. Or get out more.
Regards,
Bob
s/v Sur Le Vent
Newark, DE
MD registry