I have a 2006 mercury optimax 225 on my boat,I went out 2 weeks ago and the boat ran fine. This weekend we went out and it would not get above 3400rpms. We changed the oil sensor and it is still doing the same thing. I left the motor trimmed down in the water for 12 days and this weekend it had alot of growth from barnacles or some type worms growing on it. Was just wondering if that could have some effect on the rpm"s