84 merc I/O Loss of Power

I have an 84 Century with a 350 Chev mercruiser I/O 260 HP. I overheated the engine a few years ago and ended up getting a new Crate motor with the same specifications. Ever since the new motor was installed I don't have nearly as much power. I use to get 4,600 RPM, now I get about 3,800. The engine runs smooth at all speeds, has good compression, but feels like I need more throttle. I have checked the linkage, all fine, the butterflies are opening, fuel pick up screen is clear. Changed water separation filter. Exhaust flappers are opening and clear. Timing is set properly and I have the same prop as before.
If anyone has any ideas of what to check next, I would really appreciate it.

Thanks, Tad

Re: 84 merc I/O Loss of Power

I overheated the engine a few years ago and ended up getting a new Crate motor with the same specifications. Ever since the new motor was installed I don't have nearly as much power.

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If this has been going on for a Few Years,..............

When was the last time you bothered to do a Tune-Up,+ General Service,..??..??.............

If the motor was/ is so Down on Power,........
It Should have been dealt with Shortly after the installation Took Place