Firstly, I do have the 4-108/Paragon 1:1/Walter 2:1 V drive/17x12 LH prop. The engine has seen little use and has somewhat less than 1,000 hrs on it. Only 35 hrs in the last owner's six years before I bought the boat in March 2010.
The boat is only doing 5 knots at about 2,100 rpm. Reversing is also highly inefficient. I approach any dock at the slowest possible safe speed as stopping the boat seems to take forever and require really gunning the engine.
This performance seems totally out of sync with such a powerful engine and big prop. I would be very grateful for input about the comparative performance on other boats with the same standard set up.
I am sure the condition of my prop has a little bit to do with it. It could look better than it does with some minor electrolysis, dull and scuffed edges etc.
I also believe that a suggestion I have had from Nelson Tolar (long time 365 owner - Alabama) about the Paragon gear box slipping could be the right track. It explains why the engine never reaches 180 degrees and hovers around 140 (unless my temp gauge is faulty). It also explains why it seems easy to rev it up with little signs of strain.
In looking through the Westerbeke manuals on the boat I found a section on the Paragon gear box. It has about 2 pages talking about forward and reverse adjustments. Is this the best information to be had on the subject? The 2 illustrations and the text was not very understandable to this aging idiot, but I hope it will sort itself out once I open up the lid of the gear box and look into "the heart of the matter". All advice and hand-holding much appreciated.
I'm very interested in this conversation. My diver tells my 3 bladed prop has a lot of electrolysis and will need to be replaced. I have the same paragon direct drive sail gear and Walter v drive. But my engine is a more powerfull W58. Same motor they put in the Pearson 424. So I might benefit from a larger prop.
My questions for POG are: Have you had a diver clean the hull? and by chance is you prop a 2 bladed sail prop. They are designed for low drag and as a consequence do not work well in reverse. This might explain the sensation of your motor reving up when backing down.
Pete W.
The 140 degree temperature issue could be a bad thermostat. For under $10 and less than a half hour it is worth the effort.
I agree big time with the hull growth issue. Make a huge difference.
I also am right there with a 2 blade vrs a 3 blade. I have a three blade that I am not thrilled with and have purchased a 4 blade that I am going to try this season. I don't think the added prop drag from one more projected blade of a few square inches on an 18,000 pound hull while under sail makes a whole lot of difference. That being said, when I fire the diesel up it is time to move.
Dale
My hull is clean. My prop is almost certainly the original standard prop supplied by Pearson together with the standard engine package: three- bladed 17" dia x 12" pitch, Left Handed.
Below I will give some advice to the two of you who have replied to my post but first I will repeat what I would really like to hear from other owners with my set up:
1. How many rpm will it take to get your boat to 5 knots in relatively smooth conditions?
2. Has anyone experienced gear box slip and adjusted the gear box? Advice, please...
Now to the "prop school":
Pitch is like the threads on a screw. The more pitch the faster the screw will travel into wood. Professional sailors often refer to the prop as the "screw" - which is what it is: a screw with one thread that screws into water.
If water were like wood a boat with a prop with a 12" pitch (such as mine) would travel one foot forward for each revolution of the shaft.
Assuming this were the case, how fast would the boat travel at 2,000 rpm with a 2:1 reduction through a V drive?
Firstly, because of the reduction, the prop will only revolve 1,000 times per minute. As every turn of the prop results in one foot of travel the boat would move 1,000 feet in a minute and 60,000 feet in one hour.
A nautical mile is 6,076 feet long. Dividing 60,000 by 6,076 you find that you have traveled 9.87 miles in one hour which means your speed has been 9.87 knots.
Happily, water is not wood. It does not offer the same "bite" to the screw of the boat. There will be slippage due to this and the resistance of the hull that the prop has to push. And there may be other inefficiencies in the prop itself, cavitation, keel blocking clean water etc.
The diameter of the prop dictates the power the prop has to achieve its job of getting the most out of a given pitch. Too small a prop is like "paddling with a tea spoon". You get a lot of froth (cavitation) but no movement. Too large a prop is like paddling with a sheet of plywood. You don't have the power to do it and so - again - you are getting nowhere.
Too much pitch is much the same as too large a propeller. In the end a given engine and prop size will not be able to handle a pitch that takes the engine beyond its horse powers. Or you have to shrink the propeller (to teaspoon size).
It follows that matching pitch and prop diameter, engine size, gear reduction and the hull in question is an art.
If you are after speed you need pitch and rpm but have to size your prop so the engine can handle the package. The more resistance you put against the hull's forward movement in the form of inefficient hull shape, wind and waves the bigger the chance that you will just whip up froth with you necessarily modest prop.
If you are after power to move against a storm, strong currents, towing etc you need a large prop but will have to decrease pitch and revs to match the engine capacity. You will be going slower but you will keep moving.
Personally, I am after a set up that will move me faster in light air and windless conditions with relatively low rpm. This means that the boat may be underpowered in hard weather but: the boat has masts and sails to assist when it blows. The engine is there for when it does not.
Once again, water is not wood and there will be a loss in travel forward compared to if the prop were able to move the boat 100% of its pitch.
Very efficient hulls may loose only 30-35% of the theoretical forward movement. Inefficient set ups may only cover 1/3 of the pitch distance. I am a bit uncertain here as I don't have access to the literature I studied when I last had a propeller problem. I believe I am about right, but you can look it up.
When I had the problem I had a Yankee 30 where i changed from a direct drive Atomic 4 gas engine to a small 10 hp diesel with about a 2.4:1 reduction. There was only room for a 12" diameter prop. The problem was eventually solved by using a wing-tipped propeller (like the tips on modern aircraft). Travelling at night and seeing the phosphorescent prop wash stretching aft 30-40-50 yards behind the boat like a narrow, focused tunnel of force was a revelation in hydrodynamics. I travelled 5 1/2 knots at about 2,000 rpm and less than 1/3 of a gallon/hour.
On POG, my new P365 ketch, I have to rev up to 2,200 rpm to get to about 5 knots, which means that I am getting only 46% of the theoretical pitch travel and am loosing 54% to inefficiencies of one kind or another. For such a big prop and such a relatively easily driven hull I would say something is severely WRONG.
Once again, what rpm do others need to reach 5 knots? Has anyone adjusted the gears for slippage? Advice, please.
Lastly, I hope this was not too elementary for most of you...
Carl
Carl,
Let me start by saying Sea Dragon is a Cutter with a slightly different underbody (keel & rudder) than the sloop, pilothouse, ketch.. First some facts.. Sea Dragon has Westerbeke W40, Paragon Hydraulic PM-10L transmission (1:1), Walter RV-10 V-drive (2:1), and a 3 blade 17x11L propeller in new condition.
When motoring my tach reads 2,000 and on flat water I make a little over 5 knots via the knot meter. At 2,000 rpms I burn less than a 0.5 gallon per hour. When docking, I too must really stand on throttle in reverse to slow the forward motion even when moving at a very low speed.
Garner
Thanks Garner - Sailing Seadragon,
This is exactly the information I need:
RPM required for 5 knots in smooth water and fuel consumption too.
Hopefully I will hear from someone with exactly my configuration; Ketch, W 40, Paragon 1:1, V drive 2:1, 17x12 LH prop.
Hopefully I will also hear from someone who has attacked his/her Paragon gear box to adjust the forward and reverse.
Cheers,
Carl
Below are actual measurements made with 2 differeint P365's
My expeirience is that the boat should go 6 knots with 2000 RPM's with the W 40 Engine
2.47 ratio transmission Measured Calculated with Calculated with Calculated with Calculated with Calculated with Calculated with
Eng RPM Shaft RPM Speed w 12.5 pitch 12.5 13 13.5 14 14.5 15
1000 404.9 2.5 2.4971 2.597 2.6968 2.7967 2.8966 2.9965
1250 506.1 3 3.1213 3.2462 3.371 3.4959 3.6208 3.7456
1500 607.3 3.6 3.7456 3.8954 4.0453 4.1951 4.3449 4.4947
1750 708.5 4.25 4.3699 4.5447 4.7195 4.8943 5.0691 5.2438
2000 809.7 4.9 4.9941 5.1939 5.3937 5.5934 5.7932 5.993
2250 910.9 5.5 5.6184 5.8431 6.0679 6.2926 6.5174 6.7421
2500 1012.1 6 6.2427 6.4924 6.7421 6.9918 7.2415 7.4912
2750 1113.4 6.5 6.8669 7.1416 7.4163 7.691 7.9657 8.2403
2800 1133.6 6.6 6.9918 7.2715 7.5511 7.8308 8.1105 8.3902
2.00 ratio Transmission
Eng RPM Shaft RPM 9 10 11 12 13
1000 500 2.2204 2.4671 2.7138 2.9605 3.2072
1250 625 2.7755 3.0839 3.3923 3.7007 4.009
1500 750 3.3306 3.7007 4.0707 4.4408 4.8109
1750 875 3.8857 4.3174 4.7492 5.1809 5.6127
2000 1000 4.4408 4.9342 5.4276 5.9211 6.4145
2250 1125 4.9959 5.551 6.1061 6.6612 7.2163
2500 1250 5.551 6.1678 6.7845 7.4013 8.0181
2750 1375 6.1061 6.7845 7.463 8.1414 8.8199
2800 1400 6.2171 6.9079 7.5987 8.2895 8.9803
Hi, Garner,
this is an old thread, but hits at a sweet spot for me...
I just bought S/V Audrey (P367 #5) and want to know the best prop configuration with a setup like yours and not requiring a shaft lock to keep the prop from spinning under sail, please.
Trip jacks
979.229.0638
Let me start by saying Sea Dragon is a Cutter with a slightly different underbody (keel & rudder) than the sloop, pilothouse, ketch.. First some facts.. Sea Dragon has Westerbeke W40, Paragon Hydraulic PM-10L transmission (1:1), Walter RV-10 V-drive (2:1), and a 3 blade 17x11L propeller in new condition.
When motoring my tach reads 2,000 and on flat water I make a little over 5 knots via the knot meter. At 2,000 rpms I burn less than a 0.5 gallon per hour. When docking, I too must really stand on throttle in reverse to slow the forward motion even when moving at a very low speed.
Garner
[/quote]
My numbers are a bit differant than yours.I have a 4-108 borgwarner velva drive,Walter v-drive 3 blade 17x12 prop.My cruising rpm are 1850 my speed is 6to61/2 knots she seemes to be smooth and happy at that rpm.This is the third transmission in the boat came from Pearson with a paragon when I bought the boat it had a light weight aluminium (that all the parts fused together).So I replaced it with the Borg in 1988 I have had no problems with it.
I have the standard W-40, Paragon, V-drive, 17X12 and we turn 2100 for 5 knots in smooth water. I agree, disappointing.
We have to come in slow as reverse is very poor. We cannot back out straight either.
Ah well......