Quote:
Originally Posted by TiltonBB
That has not been my experience. In my opinion there is no substitute for cubic inches and torque.
Last season I changed from a 26 foot boat with the 8.1 375 HP motor to a 27 foot boat with the 6.2 380 HP motor. The 8.1 seemed to have twice the acceleration and overall power, much more than the boat with the 6.2 that claims 5 more HP. The 6.2 is average at best and works a lot harder to get up and go. The 8.1 never even broke a sweat and even with 15 people on the boat I could hardly tell the difference in performance.
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I can totally believe that, but you can't really compare the performance of the two engines unless they are in the same boat, with the same load, with the same drives, both propped correctly, and both running correctly. Way too many variables otherwise.
Additionally, the HP on the 375HP 8.1 might have been under-rated in order to sell more 425 HP versions of the same engine. Conversely, the 380 HP rating on the 6.2 might be over-stated in order to encourage people to pay a premium over the lower HP versions of the same engine.
I'm perplexed by Mercruiser's decision to go away from GM based engines. I think the variable valve timing, that is part of the GM marine engine line, is a massive advantage over the fixed valve timing you find in Mercruiser engines, in a marine application. It allows you to run an aggressive cam to make big HP, but still idles smoothly, pulls strongly from low RPM, and does not suffer from water reversion ingestion due to too much cam overlap at low engine speeds.