So I had some trouble installing the lower unit on a Mercury Thunderbolt 115 after replacing the water pump. I was unable to find the correct gears. I put the lower unit back on correctly and the propeller spins as it's supposed to (F N and R) hooked to water muffs. I took it to the lake and it moved the boat in reverse as it was supposed to but when I put it in forward the boat would not go anywhere but I could see water churning and the propeller moving faster as the motor idled up but it would not push the boat forward. Everything is the same as before besides the new water pump. Did I spin a hub? When I get home I'm going to try and mark it and see if it spins.