Hello all, and thank you for letting me be a part of this great forum. I've been a long time lurker, and finally registered a short while back. Anyway, I have what seems to me to be a strange issue on a Mercury M-500 (1978 4 cylinder 2-stroke). I live on a small lake and am a retired pipefitter who was in industrial HVAC service for 30 some odd years, so people think I can fix boat motors? I do have a bit of luck now and then, and I do enjoy working on them, it kind of gives me something to do. This little Mercury had the bad luck of being worked on by someone who should probably never work on outboards, it was pretty messed up. One of the main issues I found was a wire harness clamp tab pinched between the crab. and the intake causing one heck of a vacuum leak and crazy high idle as you can imagine. I finally got things going my way, and did a basic tune up including changing the lower unit lube, spark plugs, wires, and the seafoam treatment. I filled the tank with fresh high octane non-ethanol gas and synthetic Mercury 2 stroke oil. The motor starts and runs very nicely, but when it gets close to WOT, it pretty much falls on it's face. It runs fine up to just below WOT. The other strange thing is, the primer bulb never gets hard. I changed the bulb and fuel line, and even stuck the new line right down into the tank to bypass the pick up line and anti-siphon valve, but it still doesn't get hard. It won't even get hard if I disconnect it from the motor? If I pump the heck out of the primer then start it, it does smoke an awful lot, like I flooded it some. I'm wondering about the carburetors as it's obvious this other fella had at least one of them off due to the pinched clamp tab. I guess if the float height was wrong, it could go lean at WOT. Maybe I should do a high speed kill, then read the plugs? Any ideas are appreciated.