30 hp. Nissan - The Hull Truth

RGL Cape Cod · 08-17-2008, 06:00 AM

I have a 2003 30 hp. Nissan 4 stroke with carbs. I have been using the boat at least 3 times a week since april and have no problems at all till last night. I launched the boat it started right up and idled out of the harbor fine. When I gave it the throttle it came right up on plane and ran about 30 seconds then lost power. It still idles fine but if you give it more than about a third throttle it seems to lose a cylinder and skip.
I took off the fuel line after the filter and squeezed the bulb and had good fuel flow. I put some of this gas in a clear bottle and it looks fine no sign of water. I am going to change plugs today and try again but the plugs were new in April and shouldn,t be fouled on a 4 stroke unless something is wrong. Any Ideas?

A1 Outboard · 08-17-2008, 12:46 PM

Just some ideas that could give you the same problems:

Debris, water droplets, or deposits inside the carb restricting the fuel flow - usually they float around in the bowl then get into the jets

a weak fuel pump - most likely when the motor runs fine for a very short time - squeeze the primer ball as the motor slows down to see if it picks back up

possible ignition problem - use a timing light to verify each plug firing.