i think Ferm just about covered it pretty well. Fuel consuption on the 2.5s isn't that much different on the bigger boats, you will get better with a 2.4 on a lighter boat. On the heavy ones, I haven't seen much difference. i personally like merc V6's over the competitiors, That doesn't mean they are better( its hard core Yamaha country around here), they just seem to be a good comprimise between initial price, service parts priceing and availability, light weight and performance. the good thing about 2.5's over 2.4s is they have steel sleeves, if you kill more than one hole on a 2.4, its generally not worth rebuilding due to the pricing of sleeving( you can't bore the stock chrome bores), teh 2.5 can be overbored or even have the sleeves repalced(if you want to spend that much). the biggest thing I would look for on this motor( after the obvious of compresion, fire, corrosion, etc) is the swivel shaft(where it pivots when you steer), with the motor trimed down, pull up adn back on the lower unit and see if there is any slop in the pivot shaft, beware of signs of fresh grease on the grease fittings and the swivel shaft ends, thick grease can tighten up a worn out one for a short period of time. The swivel can be fixed if worn out, it just takes a lot of time and effort. you see it worn out a lot on kingfish boats from low speed s turn trolling
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