Yanmar 4JH3-TE RPM

I have a 4JH3-TE with KM4A 1:2.14 gear installed in a Hylas 49 sailboat (35,000lbs, 41.5’LWL). I am in the process of selecting/sizing a new folding or feathering prop. I currently have a fixed 18” prop with 10 pitch. With that prop the max RPM is 3,500 and the max speed is 7.5 Kn. The hull speed should be 8.4 Kn. I have been talking to several prop reps am getting different advise. I am told by some that the shaft RPM (1750) is very high and a prop sized correctly will likely cavitate. One solution is to over-prop. This may be done by increasing the prop diameter or increasing the pitch or to use a 4 blade prop.. In any case I am told it will increase thrust and should allow the boat to get up to hull speed. The maximum engine RPM will be lower however (maybe 3200 RPM). My question is: Is it harmful for the engine to overprop and run at lower RPM while producing maximum thrust? What are the consequences? Also Is there another solution? Do you know of someone I could contact to solve this puzzle?