1988 Mariah Shifting Problem

[Todd]

I have a 1988 Mariah Supra that is having a problem when shifting. The throttle accelerates before shifting into reverse causing it to slam into reverse. I think it should shift into reverse before the throttle accelerates. Is this a minor adjustment that I can take care of, or is this something that I should take to a professional to have adjusted? I just bought this boat and am not really familiar with the shifting adjustments or shifting maintenance for this boat. Any advice would be greatly appreciated.

Thanks