I've got a 2000 mercruiser 3.0 with the delco est. the boat seems to idle fine without any issues. upon accelerating the motor bogs and clatters, very similiar to what a motor that has detonation sounds like. while this is going on or shortly thereafter the tach starts bouncing erratically while under load. upon returning back to idle the needle will calm down and stop bouncing. so far i've replaced everything ignition wise minus the coil and the sensor under the distributor that connects to the ignition control module. i took it to a mechanic would was unable to diagnose. he said the base timing was correct. am i right to assume this is ignition related? would the coil be the likely culprit?