MY propellor is too BIG

[rich99uk]

I have a 22 foot semi displacment hull fishing boat with a ford transit 2.5 DI (approx 4000 rpm) engine init. with a 3:1 reduction gearbox. Thw boat is a heavy boat. The prop i have at moment is 18 x 12
At precent I am only getting about 2500 RPM max.
I was goint to take it and get a inch taking off the diamiter however i still not sure that is going to be enough or even if that would work lol.
I dont want to get it cut down and balanced then realised i have to take it back off and do it again gets a bit expensive.
So i though about trimming it down myself gradually then taking it out for test and when i get approx right RPM take it off and get it balanced proffesionally. What does everyone think ??? Any Other Ideas ????

[Frosty]

You need to reduce pitch not dia. Try ringing Lancing marine near you, they may swop or sell you a second hand one.