I recently bought a used 4tec 155 engine off ebay. The owner knows nothing about the engine. Any how I put it in the ski, I have not installed the drive shaft yet, still waiting for the parts. So I ran the motor to see how it is and it runs irregular. Idles up and down, some times when I push the throttle it idles up to about 2500 rpm and stays their until I shut it off. Its kinda hard to start, takes a few turns to finally get it to run. I changed the spark plugs already and did an oil change. Any ideas on whats up. Thanks