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Hello folks, wanted to inquire about a f90tlrc (2004). I recently hit a stump in an area lake and the lower unit is going to have to be rebuilt or replaced. I currently have a 2.31 to 1 gear ratio in the lower unit and would like to go with the 2.00 to 1. I called yamaha about the issue and was told that the power head was not designed to run that fast. The rpm range for my outboard is 5000-6000 rpms. If I change the lower unit ratio and prop to run within this range, how does this affect the power head. The motor still won't turn over 6000 rpms. Is the swap possible? I have looked at the drawing for my motor and reviewed the ones that have the 2.00 gear in them. They appear to be very close. Does anyone have both of these gears that they can visibly see if there is a difference? The gear swap would gain a theoretical increase of 8mph ( without figuring prop slip). I will currently run 54mph and would like to get closer to the 60 mark. Not a speed demon, want to bring more of the boat up to cut across waves better. I have tried several differrent props (which are expensive) haven't found the characteristics that seem to work. My boat is an x54 express, I have a jack plate (6in) and it is all the way down. This puts my cav plate about 3/4 in above the keel and works well.
Any help would be appreciated.
Any help would be appreciated.