I have an old mercury (approx 73) blueband 115hp and am having trouble getting it to run correctly. I have measured the compression at 140psi on all cyclinders, cleaned carbies (single throat), rebuilt fuel pumps and set timing as per manual 0-2 degrees before tdc primary pickup and max 23 degrees BTDC. However, there were two choices the other being 5-7 degrees BTDC and max 23 BTDC. Symptoms are max revs of 3500rpm (not at full throttle) and dies (looses rpm) if use full throttle. Fuel line size is ok. I think the engine is getting too advanced at too low a rpm????? Is 140psi ok?<br />If I reset the primary pickup to 5-7 degrees do you think this will help? Should I aim for 4800-5500 rpm max.? Should I try and set the max angle BTDC by trial and error for highest rpm?<br />The engine was rebuilt before I got it and has a serial number beginning with 800****** which is not listed in my manual but the electrics and distributor suggest its about a 1973. It has two timing marks (original I measued with dial guage represents TDC--am using this one, the second hand made mark is 1-2 degrees btdc). The decal on the ingition support suggests 23 degrees is the max BTDC to use!! Does anyone have a graph of rpm vrs advance?<br />Any help would be much appreciated