Posts: 3508
Location: Elk River, Minnesota | Hiya,
If you have the option of going 75 as compared to 60, and the 75 weighs more, it will have higher displacement and probably acts more like a weak 90hp motor if there exists a 90hp of the same displacement as the 75.
When two motors are rated differently but have the same displacement (say a 75 and a 90 in this case) the 75 is probably rated below it's tested range and closer to 81 to 82 hp and the 90 is more likely to be over-rated and closer to 82 or 83 hp. So...you really aren't going to see that much difference between the two. It is not physically possible to have a huge difference in HP with engines of the same displacement, even with modifications. If my memory is correct on my research with this (as I did this with a yamaha 90hp 2 stroke for testing purposes) I could gain some on the 90hp by switching out reeds, exhaust tuner and a shaved head, which probably only gained me another 10hp. Worth it? Not really...as I still was unhappy with the performance of the engine.
I changed from that yamaha 90hp which is had the smallest displacement of any 2 stroke 90hp out there, to a Johnson 90hp and was highly impressed with the an increase from 69.6cid to 105cid in the same HP engine and what it did for my boat. I gained some 6 - 7mph (from 37 to 43) ,increased weight by about 100 pounds, and the boat jumps out of the hole with a higher pitch prop.
The extra weight, in my humble opinion, is actually a good thing. It allows the bow to trim easier as more weight in the rear moves the center of gravity back.
So...if you can swing it, I'd get the 75....well worth the extra money as the boat will be very efficient with the larger displacement. Hole shot will be better, mid range performance will be better, and it will be faster too...
Steve
If they are of different displacement, then definitely go with the 75.
Edited by VMS 5/15/2012 9:42 AM
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