Wot e200txecm 1998

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Hello, I have a 1998 E200TXECM. I rebuilt carbs, did a lync and sync checked timing right at 18 degrees. Replaced fuel pump and tube into tank. Put a clear tube in line checking for air bubbles none solid fuel delivery. Right out of the hole she shot right on down the ICW I backed off throttle as a boat went by and she just went to 3500rpm and thats were she stayed. checked spark while on water and had on all 6 cylinders. Any ideas??? I am at a loss. Did notice today the reg/rectifier was putting out 18-19 volts as it reved up. Checked with meter and it was right there. If to much charging voltage will that cause these problems? I want to thank you for this site its great and appriciate the answers.