I have a 1966 100HP and have been thinking about picking up a parts motor since every year parts become harder to find. I found a 1969 100 HP Tower of Power that ran great this summer until reverse quit working. I know the ignition system is different but was thinking if my engine died I could take the lower unit off of my 66 and put it on the 69. I assumed it would be an exact swap until the owner of the 69 said that he had a nearly new prop that I could have for my 66 because it would not work on his 69. That made me start to wonder if the swap from 66 to 69 would work. Question is does anyone know for sure? In looking at a prop application chart it shows the props to be the same for both years. Thanks for whatever info you can give.