I have an old 1970 18hp evinrude and I'm having trouble getting her fired up. The motor sat on my garage floor after I bought it for 2 years but now I want to use it for a skiff I'm building. I changed out the plugs and cleaned the carb, but can't get her to crank up. I've never dealt with a motor this big so I don't know how easy it should be to pull the cord. It feels kinda stiff, maybe its just the size of the motor. anyway if I choke it all the way after a few pulls I'll get a big pop or backfire, but thats it. any advise? I need to figure out if this motor will work quickly or else I'll have to delay my project.