Re: repowering 25 seafari????????
There is a weight penalty with the diesel. The weight of a 1970's Mercruiser small block Chevy/pre-alpha one setup is 1021 lbs. (New 350/300 MPI w/ Alpha One is 946 lbs)
Contrast that with the weight of the Cummins-Mercruiser 4.2L ES 320hp with Bravo One drive at 1201 lbs total.
The difference between the original setup and a new 320 hp diesel setup is 180 lbs.
FUEL CONSUMPTION COMPARISONS
However the 3900 rpm (WOT) fuel consumption of the diesel is 18.8 gph, and 75% power (3200 rpms) fuel consumption is 11.7 gph, and 60% power (2850 rpms) uses only 9.0 gph. Test boat was a '99 Bayliner 2855 SunBridge repowered in '06 with CMD.
WOT fuel consumption of the 2007 Mercruiser 350ci/310hp is 23.9gph at 5250 rpms WOT('07 SeaRay 26' 240 Sundancer) 75% power fuel consumption is 18.4 gph at 4800 rpms. (60% power at 4000 rpms setting drops you to 14.1 gph)
WOT Fuel consumption of a single Mercury 250 Optimax is 27.6 gph at 6000 rpms WOT. ('08 ProLine 23' CC). 75% Cruise fuel consumption is 13.9 gph @ 4800 rpms, and 60% power at 4500 rpms burns 11.6 gph. (remember to multiply this 2X-10% for twins)
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Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.
Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!
Currently without a SeaCraft 
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury
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