For some odd reason Beneteau defines the house battery as the one forward of the engine and the starter battery as the one beneath the aft berth immediately behind the engine. The way that they are wired allows them both to be starting batteries or house batteries depending on how the switches are positioned. The only difference appears to be which batterie is initially chosen for the constant hot leads for the bilge pump etc. some boats have a third battery installed beside the battery under the aft berth. The problem is that the size of the batteries is limited due to the low clearance vertically. In my case with a 323, I nstalled spacers on all of the support surfaces for the aft berth to gain more height for the larger battery case size.
I suppose it doesn't really make any difference as to which is defined as house, and which is engine. They are probably both subjected to plenty of heat when the engine is running.
When I really got a good look at my boat's engine pan, I realized that there was not a weep hole to allow drainage to the bilge,and that is understandable due to the potential for oil to get into the bilge. I do keep an oil absorbent pad under the engine just in case of a drip and to keep it clean anyway.
In regard to the comment about water intrusion through the hatch, I suppose it is possible that water could get in that way with no dodger. However, I sail with no dodger and have not seen that as a source of significant water intrusion.