Taking the boat in for some service work and I was wondering, do I need a new housing with a impeller change? Someone told me this and would like to confirm. Also is it a waste of money to go with synthetic oil in the outdrive, as this is not a high output application. I run it in the motor but never have put it in the drive. Also has anyone ever wet sanded the bottom of the boat, would I get anything out of it besides a sore arm. The combo is a 502/415/B1 with 150hrs. Thanks