A quick check to make sure the Hotfoot is not stopping the engine control from hitting the WOT stop is what I would check first.
Since the powerhead was replaced, the rigging could be off.
For consistent top end speed testing and adjustments, always do it alone. No partner. Keep the fuel level consistent as possible. Live wells empty.
Without your friend I could see you bumping 75 mph. You may also bump the rev limiter without his added weight.
Keep us updated.
Don
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