If you hold onto the spark plug while it is running, you can find out if it is firing or not. If your hair stands straight up on the back of your neck , it is firing, If your hair lays down flat, it isn't firing.

Thank you so much for posting this. I had a similar problem with Yowell Boat Yard in Waco Tx a few years ago. They charged me for a carb rebuild that they never did. When I picked the boat up they told me it was still running horrible after the rebuils and the problem was I needed a motor rebuild. So instead of letting them do it and keeping my boat another 4 months, I took it to Prikryl Marine and asked them to rebuild my motor. They called me the next day and asked why I wanted the motor rebuilt and I told them why. They said all I needed was the carbs rebuilt and it had not been touched by whomever claimed to have rebuilt it. I was furious. They saved me all the old parts and I took them with a few choice words to Yowells and I have never set foot on Yowells property since. So Yowells Boat Yard is another place to be aware of. Oh, and after Prikryl rebuilt the carbs, the boat ran like new.

If you can hold a firing spark plug, I never want to make you mad.