A4 good stuff.....
Sorry about the delay in replying, I've been swamped at work.
I have an A4 in my 1970 E32. Most of the original fuel tanks have been replaced in the Ericsons of our vintage by now. Most have been replaced with the Tempo Plastic tanks, like mine was. I have 18 Gallons, if you think that is the type you have, you can measure / sight the size and then go to West Marine to compare what's on the shelf.
My A4 burns 1 gallon an hour at 1700 RPM, and that gives me 5.7 knots. At 2000 RPM the burn goes to 1.2 gallons an hour and speed hovers right around 6.4 smooth seas. Can be .2 higher for glassy, or lots slower for choppy. I have had the boat surfing with main only and seen 14 knots for almost a minute. The engine unloaded, but never got over 2250 RPM.
I have a 12x5 two bladed sailor prop, RH of course. The prop tips at 2000 RPM are almost supersonic, and that translates into a light tube at night in the phosphorescense.
I have added the oil cooler/oil heater, crankcase vent and oil filter to mine, Buck will try to talk you out of it, but it has really tamed mine down. I change oil and filter religiously at 50 hour intervals, and grease the water pump shaft thru the cap every fourth time I run it. I carry a complete set of ignition parts, and have a couple of good references for you if you need them.
Good luck, hope this helps.
Michael Krebs
"Voice of Reason"
1970 E32-134
King Harbor - Redondo Beach, Calif.