Michael, Get familiar with the engine bleeding process on your old Perkins. You will do it over again each time you change the fuel filters. The best reference source is the Perkins engine manual, second best, Calder's "Boatowner's Mechanical and Electrical Manual." Here is the basic process after changing the fuel filter, as extracted from the Perkins manual. Change the engine fuel filter. If a filter vent plug is fitted, unscrew the vent plug on top of the fuel filter cover two or three turns. Slacken the fuel intake to the fuel injection pump. Operate the priming lever on the fuel lift pump until fuel, free from bubbles.comes out of each vent point. Then tighten the connections in the following order: 1. Fuel filter venting screw; 2. Fuel connection to injector pump. This should get the air out of the low pressure lines. The process is made immeasurably easier if you fit a small electrical pump like a Walbro after the first fuel filter. Then it is just a matter of loosening the connections, switching on the pump, and closing the connections in the proper order. Now, since your engine has been running, try starting it up. There should be enough residual fuel in the injector pump to get it going. If it fires and keeps running, you are home free. If it starts and runs for a few seconds and then stops, there is probably air trapped in the high pressure injection pump. In this case you have to bleed the pump according to the manual instructions. If this happens, you will have to crank the engine with the starter motor. There is no compression release and it is impossible to do it by hand. During the production run of most Perkins engines, the factory changed filter housings and injection pumps for different models so one set of instructions doesn't fit all. If you run into trouble, get a knowledgable person to show you the process. It is easy after the first time. Larry Z