not sure what prop but the engine has only got anout 20 hours on it would i need a tune up or is somthing else wrong but about the cilinders my last engine it was a six cylinder and this one is a four cylinder and it is the second new engine i have tried. i only had to pay for one but the first one i had that was the problem it was only runnin on three cylinders but thisone has had a compression test and all four are firin. but what prop should i order. i do have a workin tach and get about 3800 rpm WOT i am not sure what the max reccommended rpm is. thanks