I have a new to me, 31 ft. Hunter. 2006. I finding it hard to dock . Other owners have said they went from a 2 blade prop to a 3? Can you let me know your thoughts?
thanks, Bob
thanks, Bob
props
- Thread starter bhathaway
- Start date
This seems to be the month for questions about props. 
A three blade prop will usually help but it will also slow you down some under sail. First thing I'd do is check that the blade you currently have has the correct pitch. No sailboat is going to perform great in reverse but you should be able to manuver in the harbor.
How does the boat do going forward? can you hit hull speed doing ~85% of your max rpm? can the engine achieve max rpm without lugging (i.e. no black smoke).
If not, than you should look at the current blade as needing to be repitched which will be a lot cheaper. There is no substitute for a good prop shop.
My boat (an '83 34) wouldn't do anything in reverse until I had the prop correctly pitched. I too was looking at going to a 3 blade. Once the blade was properly pitched she handled great in reverse.
This is the book to get if you really want to know about sizing & pitch of boat props.
http://www.amazon.com/Propeller-Hand...boat+propellor
If you have a Yanmar this is a good site to check for 'recomended' prop size/pitch. Note they also say a sea trial is the only way to be sure that the sizing is right. It really is an art more that a science.
http://yanmarhelp.com/i_prop.htm
In answer to your question yes, usually a 3 blade prop will let the boat back up better. I'd still check the pitch first it is a lot cheaper.
Brian
edited - answer original question & add comment about art/science.
A three blade prop will usually help but it will also slow you down some under sail. First thing I'd do is check that the blade you currently have has the correct pitch. No sailboat is going to perform great in reverse but you should be able to manuver in the harbor.How does the boat do going forward? can you hit hull speed doing ~85% of your max rpm? can the engine achieve max rpm without lugging (i.e. no black smoke).
If not, than you should look at the current blade as needing to be repitched which will be a lot cheaper. There is no substitute for a good prop shop.
My boat (an '83 34) wouldn't do anything in reverse until I had the prop correctly pitched. I too was looking at going to a 3 blade. Once the blade was properly pitched she handled great in reverse.
This is the book to get if you really want to know about sizing & pitch of boat props.
http://www.amazon.com/Propeller-Hand...boat+propellor
If you have a Yanmar this is a good site to check for 'recomended' prop size/pitch. Note they also say a sea trial is the only way to be sure that the sizing is right. It really is an art more that a science.
http://yanmarhelp.com/i_prop.htm
In answer to your question yes, usually a 3 blade prop will let the boat back up better. I'd still check the pitch first it is a lot cheaper.
Brian
edited - answer original question & add comment about art/science.
Your main concern seems to be docking and although a prop change could be helpful it will not eliminate your issues. Go to the archives as there is a wealth of information about backing up and docking a sailboat. In a nutshell you need to become familiar with the boat to see how it will react under varied conditions. Learn to use any "prop walk" to your advantage. Learn the use of spring lines to help steer the boat. Make observations of wind and current to anticipate how the boat is going to react and what you need to do to supplement or counteract those movements. The ultimate solution comes with lots of practice and even then in certain conditions even seasoned sailors will foul up a docking maneuver.
Some years ago, on this site, I read some great advice on backing our 1990 Hunter 33.5 sailboat. The advice was to stand FORWARD of the Steering Pedestal facing AFT. This gives you much better control than facing forward and looking back over your shoulders. Just remember that the Throttle lever now goes in the opposite RELATIVE direction. Away from you to increase speed and toward you to reduce speed. I now always this method fo backing into slips or longer distances.
The prop that Hunter put on the 1990 33.5 was a 16 x 11 (16" Dia & 11" Pitch). This turned out to be a compensation for the 2 Cyl. 2GM20F engine which was undersized for this boat. After some routine engine maintenance work (new Injectors) the deisel mechanic took the boat out for a test run. His comment afterward was the the boat seemed to be "Over Propped". On investigation I found that Hunter originally had used a 15 x 11 prop for that model (until they discovered it was under powered with the 2GM20F. (The following year that model had the 3GM30F engine. Net result was that I had a good prop shop cut down my 16 x 11 prop to be a 15 x 11 prop. I can now easily go to ( and over) 3000 RPM without Black Smoke. The engine is much happier now and can run all day at 3000 RM, where it was limited to about 2800 RPM before.
The prop that Hunter put on the 1990 33.5 was a 16 x 11 (16" Dia & 11" Pitch). This turned out to be a compensation for the 2 Cyl. 2GM20F engine which was undersized for this boat. After some routine engine maintenance work (new Injectors) the deisel mechanic took the boat out for a test run. His comment afterward was the the boat seemed to be "Over Propped". On investigation I found that Hunter originally had used a 15 x 11 prop for that model (until they discovered it was under powered with the 2GM20F. (The following year that model had the 3GM30F engine. Net result was that I had a good prop shop cut down my 16 x 11 prop to be a 15 x 11 prop. I can now easily go to ( and over) 3000 RPM without Black Smoke. The engine is much happier now and can run all day at 3000 RM, where it was limited to about 2800 RPM before.
Agree with previous poster, do a search of the archives. There are no less than a dozen threads on props and performance that you will find very helpful.