Once again. The 150 is rated rated differently than 115 and I dont mean the number is different . Its like you were explaining to someone from Europe how your boat will go 60. Theyr'e thinking in Kilometers and arent impressed. Apples and Oranges. Before 1982 Mercury rated its L6's at the crank. After 1981 they rated them at the prop. The old 150 crank rated motor is now the 115. Its the same thing. They did a few other changes at the same time that made the newer 115 a better motor than the old 150. Where it gets confusing is that Mercury introduced the 150HP V6 in 1978 and decided to start calling their old 150 HP L6 the 140 HP so the buying public wouldnt get confused . Then it became the 115. Same motor internally give or take very minor differences you wouldnt ever notice. The mid 80's 115 might not walk away from the old 150 because its essentially the same thing. same cubic inches, same reed cages and reeds, same carbs except for the economizer circuit, same porting, same "direct charge" power ports and ALMOST the same pistons ( dunt care less compression ) . the 80's 115 will run longer with less screwing around with it though.
The old 115 is a different motor than the 80's 115. I understand its easy to get confused given they use the same number. The lower uses up a good bit of power although Mercury never bothered trying to use actual horsepower numbers in its advertising. The 80's 115's were more likely 125-130 HP at the prop and they were more like 145-155 at the crank and the old 150 was probably about the same.
Cars went through the same thing in the early 70's when they changed the way they reported HP. 325 HP became 250 HP and a generation of souls was lost.
