Hi guys the motors are yamaha 80's and 100's and the same merc engines are called 75's and 90's This is when merc and yamaha were cooperating with each other . The powerheads were from yamaha same with the merc 50's so if you bought a merc 50,75,or 90 you really were getting a yamaha with better access to better props and better corrosion protection also same with the f-115 or merc 115 four stroke or the merc 225 . just a little history lesson for those who like that kind of stuff .WE would sell the Pro-line with merc 225 and pull the cowling off to show it was a yamaha . The engines on the tomcat 24 are four stroke yamaha 1.6 litre engines with carburator then the upgrade to fuel injection with the f-115 also increased to 1.7 litre I"ve had two of the f-115 i love them great engines . whoever does buy this boat make sure you do an engine run and boat test good luck Jim of Jennykatz