47' Gulfstar 47 Sailmaster prop size

[The Phoenix]

I have a 1979 Gulfstar Sailmaster 47 and am looking to replace my propeller. It came with a left hand 20x 16 3 blade with one and a half inch bore. A friend that had a sale master had a four blade prop. I was wondering if anybody else has any input on what they might have. My engine is a Perkins Sabre M135. Thanks for any response.

[FPNC]

Call or e-mail a reputable propeller shop.
Tell them the displacement and water line length of the vessel.
Tell them the engine HP and maximum operating RPM and also the gear reduction and rotation and shaft size.
Tell them the maximum diameter propeller that will fit under the vessel.
They will recommend the correct propeller.

[The Phoenix]

I'm on it. Thanks😁 I know prop sizing is dependent on lots of things but I was just curious what other owners of Gulfstar Sailmaster 47s had experienced. Thanks again for your response.
I have an Electroguard 208 corrosion protection on board and am wondering how effective it really is. Does anyone else have an opinion?

[Alawaiorion]

Originally Posted by FPNC

Call or e-mail a reputable propeller shop.
Tell them the displacement and water line length of the vessel.
Tell them the engine HP and maximum operating RPM and also the gear reduction and rotation and shaft size.
Tell them the maximum diameter propeller that will fit under the vessel.
They will recommend the correct propeller.

Yes this! We had a disintegrating auto prop that we had to replace with the spare fixed three blade prop that came with our boat (17 years of sitting in the aft lazarette finally used LOL) ended up that we were over propped 18 RH 16 pitch for a 48 Celestial 185 Perkins so we contacted Olympic Prop in Anacortes ( being in Hawaii that's the closest place for us) and we did the RPM test and gave them all the information and ended up with a new prop 18 RH 14 pitch - the cool thing was after our diver put on the new prop we were able to send the old one which was still in good condition back and for under 300 dollars we got it re-pitched from 16 to 14- so now we have a good back up prop-

An interesting thing about the auto prop / feather prop and why we opted not to replace it was the $$$$$ and we had a LOT of prop walk in reverse compared to the fixed three blade and the blades ended up disintegrating due to electrolysis because of where the sacrificial zinc was - we are not racers and I get how people like them but they weren't for us -

I wish I had seen a thread like this 2 years ago - I'm sure there was one but I never found it googling- I had to find this all out all on my own by calling various prop shops and grilling divers who do a lot of prop work-
comical note: amazing to find out that MOST sailors have no idea of the diameter and pitch of their prop - ( the most common response: "Uh I have the one that came with the boat when I bought it") I thought I'd find some boats of a similar size to mine and ask but I'd just get a "deer in the headlights" look - amplified as it was never a question expected from a woman -