I need to replace my 20HP Merc manual start. I have a shoulder injury that makes starting the engine and tilting the engine very difficult. I see in the info on the 25 HP that it has tilt assist. I can't find out much about it. Is it like a gas shock? Does it really help a lot. I was also looking at a Yamaha 25 but their tilt assist is only available with a 20" shaft. I need a 15".