Took the boat out yesterday and on the way back engine would not rev over 2500rpm. Running very rough. Drained bowl on filter still not good. So bracing myself for a 10kphr 40 k trip home (might as well troll} after about 1/2 an hour motor kick in and ran sweet. Then after 10 minutes went back to the 10klmh speed again. Got back to the ramp just on dark. Think it could be a faulty coil? Looked up on net and it is recommended that all coils be replaced. Motor has another year on warranty. Any thoughts re replacing all coils or just 1 that';s if it is a coil.Also any ideas on how i can test the coils?