I bought a rude motor from a guy 3 years ago. I put it on a 18 foot john it has a whale tail on it. it seems to smoke going up out of the hole.. the thing is it doesn't seem to go fast. it was on a 20 foot pontoon boat b4 does the size of the prop matter? i have found that if i don't trim the motor back down b4 taking off the whole back of the boat will come out of the water and i loose contact with the water. do i need to look for a smaller prop? and if i need a diffrent prop what size do i look for?