I sent my Martec prop in and had it refurbished to the tune of $185. It needed it, but I am still experiencing the following problem; I run the boat in forward at 2500 rpm for example, slow to 1000 rpm for a couple minutes, then when I throttle up again, I get a bad vibration that feels to me like one ear of the prop is not open completely. I sent Martec an email about it and their response was;
"Over the past few years, the slipping clutch (Yanmar engines 10+ years old) problem has come to our attention when we have reconditioned a customer's propeller & upon launch, customer has contacted us to report same problem still occurring after our service."

I sent another email asking if they were saying the vibratition was the slipping clutch, or that the slipping clutch was causing the prop to not open all of the way. They did not respond. I don't believe the clutch is slipping and don't think just slowing down, then speeding up again would cause it to slip. I usually have to go to full throttle until the vibration stops, then back off to the desired speed.

Anyone out there with similar experiences that can shed some light on how to resolve this problem? Is the clutch something that needs to be serviced over time? If so, is it a major job or something that can be managed by a back yard mechanic such as myself?

AC