My boat is rated for 175 HP. At the time of purchase it was equipped with the 150 and while I wanted the 175 and was willing to pay the difference, the dealer didn't have a 175 in stock, so I came home with the 150. Six months later, I'm really wishing that I had the extra 24 horsepower.

I've read numerous places that the only difference is the ECM. I've also read a few places that it is the ECM and different porting on the heads.

Does anyone know what the actual differences are and if I can easily convert my 150 into a 175?

I know that I can have the heads reworked by Hydro Tec and have no doubt that I will gain at least 25 horsepower, but this gain comes with running higher compression and higher (91 to 93) octane fuel. Where I live, the highest octane gas I can find is 90 in town and our nearest lake only has 89 octane, so this could be a potential problem. I know that I could add octane booster, but that's just one more thing that I'd have to put in my fuel tank (I'm already using Ring-Free Plus and Startron).

Also, from my research, it appears that gasoline with 10% ethanol (that's all we have around here) can lose 1 to 2 octane points during storage, so 90 on the pump display may actually be closer to 88.

If I can gain 25 HP with an ECM change-out, then I can still run mid-range (or the locally available 90 octane) with the lower compression factory heads.

Any help, advice or suggestions would be greatly appreciated