I would ask this on the Mercury forum but I do not have my serial number handy Was fishing Friday and my Caymas was performing awesome early on, it done went and got hot that afternoon, 95 degrees, I noticed my 300 R was struggling to get out of the hole, I even checked to make sure my livewells were empty. Saturday morning was just the opposite, a cool front had blown in, the boat jumped out of the hole like a bottle rocket, so my long winded question, does the heat and humidity make a big difference on these 4 strokes ?