I have a Talon 22 tunnel with twin Mercury High Performance 1993 2.5 liter carb engines (245HP). Back in '97 I added a 110HP Nitrox nitrous system for each engine. The engines have 270 hours on them.
Last weekend when pulling off the trailer something didn't sound right on the port engine. That unmistakable metal "sound". Anyway, we pulled the boat out and went home. Turns out the upper crank bearing shot craps. No signs of overheating, it just failed and half the needle bearings fell out and damaged the crank. Some material got past the crank seal ring and into the number one cylinder.
I've made the decision rather than spend the money rebuilding I'm just going to buy two new partial power heads and have two fresh engines again.
A partial power head basically includes everthing behind the reeds less electronics. My carb intake will bolt right up. I've been told the back half of the block will have the latest changes that have been incorporated in the new 280 MercHP. Does anyone know all the changes that have been made? I've been told the exhaust cavity is no longer divided and is open and the head bolt pattern has changed. Has the porting changed? Has anyone made a swap like this? Should I look into upgrading the stock tuner?
Thanks for any help.