I'm having a similar issue on my Beneteau 440 and was looking for some help too. I've just changed from the Perkins you have to a Yanmar 54 and its not allowing me to take the revs over 2200 (she should be a 3200).
Im in Slovakia and boat is in Fort Lauderdale and I have had the boat pulled in my absence in the past and found they overrun and cost a fortune unless I'm there. I dont want to loose 3 days whilst they pull her, take the old prop off and get a new one sorted so asked for one to be made up for me ready to install myself underwater on my next trip in 2 weeks when I go to the Bahamas.
I've been quoted $1200 and a 4-6wk delivery time! Fella, if I do get mine sorted, your welcome to the old prop.. Can anyone advise what I need. Its on a 30mm shaft just to add to my woes!