Have Boat Questions? Ask a Boat Repair Expert.
Hello Mike. My name is Tan.
You have one of 2 things here either loss of spark on one or more cylinders or fuel starvation. We can do a couple of tests. The first test is to run the boat and when it starts to act up squeeze the primer bulb does it run better? If yes then get an auxiliary fuel source and run the boat on the aux source. Does engine run better?
The squeezing of the primer bulb tells us if we have a failing fuel pump or fuel restriction. The aux fuel tank verifies which is the problem.
If no change with either of these tests then we have a spark issue. This test will require a timing light to check spark when the engine is acting up. Connect the timing light to the top cylinder run the boat till it acts up. When it starts acting up watch the flash of the timing light it should be steady with no dead spots. If good move the light to the next cylinder do the same test. If you find a misfire move that cylinders coil to a known good firing cylinder. If the misfire moves that is the bad coil. If it stays we have another ignition component failing.
Post back with your findings of these tests and we can continue.