I have a charity 501c3 and put a boat together to take wheel chair bound vets out on the water, free. I have a pair of 1987 220 hp carbureted Crusaders, starboard runs fine, port, ser. # 64760 model # LH220 starts fine, idles fine, runs to 1900 rpm or so fine and then won't go higher and knocks like bad gas. I have read all of the suggestions here plus we have done the following, all with no change: We have replaced all gas filters, full tank of fresh marine gas, replaced intake manifold gaskets, adjusted hydraulic valves to specs, swapped P&S carbs, timed engine with light and vacuum gauge, all with no improvement. Can anyone help? My only other thought is the weights in the distributor being defective. They were visually inspected and seemed OK? Being a charity, I cannot chase rainbows and spend money unless I'm sure of rectifying the problem. Can I temporarily swap distributors? (will the gears at the bottom of the distributor shafts be the same?) If this solves the port problem and transfers it to the starboard, then I know what to spend money on. The Prestolite distributors and/or parts are not available anymore. BTW exhausts are completely new all the way and sound unrestricted. Captain Joe, Stuart, FL