I am looking for a diagram of a 1977 evinrude 85hp engine - so i can work out how to remove the tilt rams from the engine to check if they are working correctly

Russ, not sure on factory compression, forums say motor should be good if running 100+, more important is to be with in 10% from highest reading to lowest compression reading. Balance is a key part for engine to run good. Check the attached links,instruction and guides, Good luck
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http://www.iboats.com/basics/find_engine_compression.html
Two problems with 1977 Evinrude 115HP Two Stroke Need some help The Hull...
One Cylinder down on Compression

evinrude 1978 -1979 have a capacity discharge ignition unit as the control for the spark system
it runs wires to an ignition coil
so I would be suspicious of that unit
check all connections for corrosion and bad connections
I typed in electrical schematics for 1978 evinrude out board engine and found a site --www.maxrules.com which in the list of schematics has 55hp 1977-1978
press on that and you get a schematics of the wiring diagram evinrude 1978-1979 55hp
now I am aware that you state that yours is 35 hp but if it has 2 cylinders then it is a fair bet that the wiring diagram will be the same
any way there are plenty of other sites that may be of benefit

Depending on age, the controls(relays) are either under the cowl or in a remote box but they are the same. Look for a fuse. Blown, you will have no action. Then check all connections especially to positive battery. but a bad ground will shut it down also.

They always lock in reverse. Sometimes the adjustment is slightly off.
adjust shift lever.

LIGHT GREASE SHOULD HOLD BALL BEARING IN PLACE DURING REASSEMBLY

The 70s Johnson or Evinrude outboards of similar sizes did not have any charging system. I had an old Johnson 50HP (key injection) mounted on an 18Ft Zodiac and I needed to remove and recharge the battery once every couple of weeks. Keep the battery dry and the contacts well greased.