My 1988 Catalina 30 is powered by a 14 hp Universal Diesel (M-18) with a two-blade prop (standard factory set up). We plan on taking the boat over to the coast to explore the coast (ICW a good portion of the trip) and I realize that tidal currents in Georgia and the Carolina's requires appreciable power to make way. The issue of changing to a three-bladed prop is the big topic now with the expectation that the extra blade would add a bit more push and improve backing, and manuevering in docking situations. The M-18 presently has only 450 hours and runs like a top with lots of life left, so repowering is out of the question. For those who have had the experience with both props on the same vessel and engine, is it worth the change? Will I really see some added benfit? Please chime in. Appreciate the feedback Bob
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Another Idea
Bob, If you're thinking about buying a new prop you should at least consider a feathering prop. This will give you a lot more control and power in a backing situation, will be less drag and three blades would be the way to go. A Martec 3 blade for your boat is probably less than $2000 Good Luck!
Bob, If you're thinking about buying a new prop you should at least consider a feathering prop. This will give you a lot more control and power in a backing situation, will be less drag and three blades would be the way to go. A Martec 3 blade for your boat is probably less than $2000 Good Luck!
fixed 3 blade experience
I have a 1981 Hunter 30 with a Yanmar 15HP diesel. We switched from the factory 2 blade to a full (not the slim "sailing") 3 blade. There is definitely an increase in drag under sail (I have never tried to measure it, but probably at least 1/2 a knot loss. Under heavier wind the boat will still come right up to hull speed, so it is not too big of an issue. The 3 blade didn't help with prop walk, and it is actually a bit worse. The good thing is that you can easily use the prop walk to rotate the boat 180 degrees if you want to. I have gotten used to the prop walk, so it dosen't bother me. The thing the 3 blade will give you is thrust, and lots of it! The ability to get the boat moving and punch through waves is much stronger with the 3 blade prop. We installed it becaue the tide going from our marina into the bay can be very strong, and we wanted to be able to over come that. The 3 blade will let the boat do that, no problem.
I have a 1981 Hunter 30 with a Yanmar 15HP diesel. We switched from the factory 2 blade to a full (not the slim "sailing") 3 blade. There is definitely an increase in drag under sail (I have never tried to measure it, but probably at least 1/2 a knot loss. Under heavier wind the boat will still come right up to hull speed, so it is not too big of an issue. The 3 blade didn't help with prop walk, and it is actually a bit worse. The good thing is that you can easily use the prop walk to rotate the boat 180 degrees if you want to. I have gotten used to the prop walk, so it dosen't bother me. The thing the 3 blade will give you is thrust, and lots of it! The ability to get the boat moving and punch through waves is much stronger with the 3 blade prop. We installed it becaue the tide going from our marina into the bay can be very strong, and we wanted to be able to over come that. The 3 blade will let the boat do that, no problem.
Interesting Responses
Thanks. That feathering prop is a tad bit expensive overall. The three blade "drag" experience sounds like their would have to be a trade off for the overall thrust increase as opposed to the drag in overall speed under sail. Considering that 80% of our crusing will be ICW and tidal currents and wakes are to be reckoned with, I would sacrifice the 1/2 knot under sail for the confidence for speed when needed. If I had the M-25 (20+ hp) their would be no concerns about going to a three blade, but the 14 hp M-18 is just on the edge of what is acceptable in the Catalina 30 to overcome ICW conditions in many locations. I have yet thrown into the equation inlet and ocean conditions. Regards Bob
Thanks. That feathering prop is a tad bit expensive overall. The three blade "drag" experience sounds like their would have to be a trade off for the overall thrust increase as opposed to the drag in overall speed under sail. Considering that 80% of our crusing will be ICW and tidal currents and wakes are to be reckoned with, I would sacrifice the 1/2 knot under sail for the confidence for speed when needed. If I had the M-25 (20+ hp) their would be no concerns about going to a three blade, but the 14 hp M-18 is just on the edge of what is acceptable in the Catalina 30 to overcome ICW conditions in many locations. I have yet thrown into the equation inlet and ocean conditions. Regards Bob
Prop
I have a 1988 Catalina w/25xp. Last spring swapped out the stock 2-blade for a 3-blade Campbell Sailer. Very happy with results, very slight loss of speed under sail was exchanged for reduced vibration, increase in thrust and better control under power. Although there is still prop walk to port in reverse, now that I can get the boat moving more quickly it is easier to overcome when neccessary. If I didn't want new sails, electronics, refrigeration, maintenance items etc. I would have gone with a folding or feathering prop and maybe been only marginaly more satisfied with the results. Here is the website-www.westbynorth.com....also,there is a lot of info on this subject in the archives it's worth your time to look thru it. Have a good trip!
I have a 1988 Catalina w/25xp. Last spring swapped out the stock 2-blade for a 3-blade Campbell Sailer. Very happy with results, very slight loss of speed under sail was exchanged for reduced vibration, increase in thrust and better control under power. Although there is still prop walk to port in reverse, now that I can get the boat moving more quickly it is easier to overcome when neccessary. If I didn't want new sails, electronics, refrigeration, maintenance items etc. I would have gone with a folding or feathering prop and maybe been only marginaly more satisfied with the results. Here is the website-www.westbynorth.com....also,there is a lot of info on this subject in the archives it's worth your time to look thru it. Have a good trip!
another 3 blade advantage
is you will be pleased how much the three blade will "smooth" out the drive train. that was the reason I put a three blade on my boat. It was a big difference over the 2 blade. You will really appricate this when you are under power a long time. I did not even notice any more "drag" three blade vs. two blade.You will also be able to run at a slightly reduced rpm. For what it is worth I have a three blade "Michigan Sailor" prop (appx $500) and am very happy with it.
is you will be pleased how much the three blade will "smooth" out the drive train. that was the reason I put a three blade on my boat. It was a big difference over the 2 blade. You will really appricate this when you are under power a long time. I did not even notice any more "drag" three blade vs. two blade.You will also be able to run at a slightly reduced rpm. For what it is worth I have a three blade "Michigan Sailor" prop (appx $500) and am very happy with it.
Engine RPM *Smoke*
There seem to be a lot of statements about how a, say, 3-blade prop will allow you to motor at reduced RPMs as compared to a 2-blade prop; however, there is something to consider. Namely, an internal combustion engine is optimized at a particular RPM. By "optimized", that means there is an optimum horsepower/amount of fuel burned. Additionally, particularly for a diesel engine, it is further optimized to run at a certain RPM in order to keep the flow of carbon flowing through the system and dumping it into the air (that we all breathe). Reduced RPMs will cause increased carbon buildup. The OEM prop *should* be designed for the particular engine and boat speed it is attached to. Changing props should not cause any change in either RPM (remember, you're running at optimum RPMs) nor boat speed (because speed is directly proportional to Work). Remember that diesel work engines, like what are used in boats, are far more critical for optimum RPMs than are automotive gas engines. Also, if the prop isn't pitched enough the engine won't have to work as hard for a given optimum RPM and it will smoke causing the transom to soot up. A sooty transom is a good sign the prop is under pitched. Prop Vibration: vibration will result if a prop is out of balance. Before dumping money on a new 3-blade prop it would be advised to have the old prop checked by a good prop shop for balance. If it is out of balance then have it properly balanced and see if there is any change in vibration. Prop drag: In an analysis about changing to a FIXED 3-blade prop you should not only consider the incremental drag from the fixed 2-blade but also the additional drag from having a feathering/folding prop. The increased drag of a Fixed 3-blade over a feathering prop is huge! The drag of a 3-blade will guarantee you will motor more and sail less - and inhaling all that diesel soot! Remember, manufacturers put fixed-blade props on their boats for only ONE reason - not because they are good but because they are CHEAP!
There seem to be a lot of statements about how a, say, 3-blade prop will allow you to motor at reduced RPMs as compared to a 2-blade prop; however, there is something to consider. Namely, an internal combustion engine is optimized at a particular RPM. By "optimized", that means there is an optimum horsepower/amount of fuel burned. Additionally, particularly for a diesel engine, it is further optimized to run at a certain RPM in order to keep the flow of carbon flowing through the system and dumping it into the air (that we all breathe). Reduced RPMs will cause increased carbon buildup. The OEM prop *should* be designed for the particular engine and boat speed it is attached to. Changing props should not cause any change in either RPM (remember, you're running at optimum RPMs) nor boat speed (because speed is directly proportional to Work). Remember that diesel work engines, like what are used in boats, are far more critical for optimum RPMs than are automotive gas engines. Also, if the prop isn't pitched enough the engine won't have to work as hard for a given optimum RPM and it will smoke causing the transom to soot up. A sooty transom is a good sign the prop is under pitched. Prop Vibration: vibration will result if a prop is out of balance. Before dumping money on a new 3-blade prop it would be advised to have the old prop checked by a good prop shop for balance. If it is out of balance then have it properly balanced and see if there is any change in vibration. Prop drag: In an analysis about changing to a FIXED 3-blade prop you should not only consider the incremental drag from the fixed 2-blade but also the additional drag from having a feathering/folding prop. The increased drag of a Fixed 3-blade over a feathering prop is huge! The drag of a 3-blade will guarantee you will motor more and sail less - and inhaling all that diesel soot! Remember, manufacturers put fixed-blade props on their boats for only ONE reason - not because they are good but because they are CHEAP!
Wow! I didn't find a word to disagree with!
Then I saw who wrote it! Should have known. Hi John. P.S. Well, maybe the part about sooting while under pitched.
Then I saw who wrote it! Should have known. Hi John. P.S. Well, maybe the part about sooting while under pitched.
OKay, so what's the bottom line?
Very interesting responses. The folks who added the three blade over the two blade have not disclosed issues relative to drag, smoking, transom soot, backing, accelerated engine wear, etc. However, others are saying that the three blade may cause issues that go beyond the engineering and design criteria for the engine. I can probably research the whole prop issue to a far greater extent and turn myself green doing it. My circumstance is quite simply, I bought a vessel with a 14 horsepower diesel rather than a 21 horsepower diesel. That extra horsepower is like driving a Yugo against a Porsche. I know from first hand experience that the ICW can be tough in many areas, particulary the mid-southern states and that extra power regardless if it comes from a three bladed prop or a team of manatees harnessed and leading me forward is what I need. When the time comes to haul out the vessel and recommission on the coast, that is the time I can make the change to a three blade. Hey, if it all goes haywire I can always pull over and change back to my two bladed spare. Regards Bob 30 Catalina
Very interesting responses. The folks who added the three blade over the two blade have not disclosed issues relative to drag, smoking, transom soot, backing, accelerated engine wear, etc. However, others are saying that the three blade may cause issues that go beyond the engineering and design criteria for the engine. I can probably research the whole prop issue to a far greater extent and turn myself green doing it. My circumstance is quite simply, I bought a vessel with a 14 horsepower diesel rather than a 21 horsepower diesel. That extra horsepower is like driving a Yugo against a Porsche. I know from first hand experience that the ICW can be tough in many areas, particulary the mid-southern states and that extra power regardless if it comes from a three bladed prop or a team of manatees harnessed and leading me forward is what I need. When the time comes to haul out the vessel and recommission on the coast, that is the time I can make the change to a three blade. Hey, if it all goes haywire I can always pull over and change back to my two bladed spare. Regards Bob 30 Catalina
bottom line?
Bob, the bottom line is yours, as it is your boat and your wallet spending the money.I do not think the soot is a issue,the engine will still run in the correct operating range of rpm if you have the boat,engine and prop matched correctly. This is best done by a good prop shop.As far as the lower engine speed I said it would be SLIGHTLY lower maybe only 100 to 150 rpms but still with in operating rpm range if the prop matches the boat and engine, and if so you will have no more "soot" then you have now,if any at all, You should not have any soot to speak of now or it is indication that there is something else going on. I used to run my engine at 2900 to 3000 rpm at cruise speed and was able to lower it to 2800 to 2900 with the new prop only a slight reduction but still with in the manufactures spec for operating the engine and still have plently of "extra" if and when needed.As far a "extra drag" there is no argument the the three blade has more the two but the fixed two blade has more the a folding/feathering blade so not sure if it is a fair comparison, Check the web site for Michigan props and Cambell prop there are detailed graph with drag info.I just don't see a big big deal about the extra drag unless you are racing and then a true racer would not have any prop at all because all props have some drag.Based on you plan to run the ICW you (IMO) would do well with the three blade prop (provided it is matched). To be more specific to you concerns, as far as increased engine wear there should be none,no soot,some,not lots of extra power/thrust and any prop pull you have know will be the same if not a slight increase. I also noticed less vibration and everthing was smoother,I was on a freinds boat with the exact same engine and trans as mine except he had a three blade fixed vs my two blade fixed and there is a big difference in vibration and smothness,I changed mine to a three blade fixed and got he same results.As far as drag under sail I did not notice enough as to make much differnce,just my observation, You won't get a argument about a folding prop has less drag then a fixed blade prop but the diffence is price (about $2000) so the bottom line is you and what you want to spend and what you need for performance. I will caution that no matter what you do a prop will not change you engine power and a 14 hp is still a 14 hp just no getting around that ! You should spend some time talking with a good prop shop and run some numbers with them for you personal situation for best results. Good Luck !
Bob, the bottom line is yours, as it is your boat and your wallet spending the money.I do not think the soot is a issue,the engine will still run in the correct operating range of rpm if you have the boat,engine and prop matched correctly. This is best done by a good prop shop.As far as the lower engine speed I said it would be SLIGHTLY lower maybe only 100 to 150 rpms but still with in operating rpm range if the prop matches the boat and engine, and if so you will have no more "soot" then you have now,if any at all, You should not have any soot to speak of now or it is indication that there is something else going on. I used to run my engine at 2900 to 3000 rpm at cruise speed and was able to lower it to 2800 to 2900 with the new prop only a slight reduction but still with in the manufactures spec for operating the engine and still have plently of "extra" if and when needed.As far a "extra drag" there is no argument the the three blade has more the two but the fixed two blade has more the a folding/feathering blade so not sure if it is a fair comparison, Check the web site for Michigan props and Cambell prop there are detailed graph with drag info.I just don't see a big big deal about the extra drag unless you are racing and then a true racer would not have any prop at all because all props have some drag.Based on you plan to run the ICW you (IMO) would do well with the three blade prop (provided it is matched). To be more specific to you concerns, as far as increased engine wear there should be none,no soot,some,not lots of extra power/thrust and any prop pull you have know will be the same if not a slight increase. I also noticed less vibration and everthing was smoother,I was on a freinds boat with the exact same engine and trans as mine except he had a three blade fixed vs my two blade fixed and there is a big difference in vibration and smothness,I changed mine to a three blade fixed and got he same results.As far as drag under sail I did not notice enough as to make much differnce,just my observation, You won't get a argument about a folding prop has less drag then a fixed blade prop but the diffence is price (about $2000) so the bottom line is you and what you want to spend and what you need for performance. I will caution that no matter what you do a prop will not change you engine power and a 14 hp is still a 14 hp just no getting around that ! You should spend some time talking with a good prop shop and run some numbers with them for you personal situation for best results. Good Luck !
Great discussion
I think it's clear that the big advantages go to a folding or feathering prop. I also understand that a properly designed 2 bladed fixed prop will provide the same power as a properly designed three blade prop. The only advantage (in driving the hull) for a three bladed prop is an improvement in acceleration. You should get up to speed faster, and recover better after meeting a wave. So three blades will do better into the waves, but not into the tide. On flat water, our OEM fixed two blade prop and underpowered one lung SB8 Yanmar will drive Lady Lillie at 5+ knots, over 80% of hull speed. When the wind and waves are up, we sail, naturally. If we need some punch through the waves coming into port, then we may use the close hauled main. (That also steadies the boat in the channel.) The way to get more power is to upgrade your power plant. David Lady Lillie
I think it's clear that the big advantages go to a folding or feathering prop. I also understand that a properly designed 2 bladed fixed prop will provide the same power as a properly designed three blade prop. The only advantage (in driving the hull) for a three bladed prop is an improvement in acceleration. You should get up to speed faster, and recover better after meeting a wave. So three blades will do better into the waves, but not into the tide. On flat water, our OEM fixed two blade prop and underpowered one lung SB8 Yanmar will drive Lady Lillie at 5+ knots, over 80% of hull speed. When the wind and waves are up, we sail, naturally. If we need some punch through the waves coming into port, then we may use the close hauled main. (That also steadies the boat in the channel.) The way to get more power is to upgrade your power plant. David Lady Lillie
Thanks Guys
Good thread here............ I have time to look into the three blade prop availability before I haul out and transport. I indeed do not expect an increase in horsepower in a three-blade. That is foolish thinking; however, if indeed I can gain a bigger bite when fighting those wakes, or to overtake or need that added thrust to make way through a current, without damaging or stressing the M-18, then its worth the price. I searched for over a year for a shoal draft, bristol Catalina 30 (1988) and jumped right on the purchase when I saw it. Unfortunately, it lacked the upgraded M-25 Universal. The earlier 11 hp model rendered hundreds if not thousands of complaints about being underpowered, especially in a seaway. Catalina then moved to the M-18, 14 hp, which is in my opinion on the edge of acceptable for long run powering (coastwise). The M-25 (21 hp) came in as an option, before becomming the standard power today. I greatly appreciate the feedback and enlightened conversation. I am surprised no one chimed in and said, "sell the damn thing and buy a trawler"! Bob
Good thread here............ I have time to look into the three blade prop availability before I haul out and transport. I indeed do not expect an increase in horsepower in a three-blade. That is foolish thinking; however, if indeed I can gain a bigger bite when fighting those wakes, or to overtake or need that added thrust to make way through a current, without damaging or stressing the M-18, then its worth the price. I searched for over a year for a shoal draft, bristol Catalina 30 (1988) and jumped right on the purchase when I saw it. Unfortunately, it lacked the upgraded M-25 Universal. The earlier 11 hp model rendered hundreds if not thousands of complaints about being underpowered, especially in a seaway. Catalina then moved to the M-18, 14 hp, which is in my opinion on the edge of acceptable for long run powering (coastwise). The M-25 (21 hp) came in as an option, before becomming the standard power today. I greatly appreciate the feedback and enlightened conversation. I am surprised no one chimed in and said, "sell the damn thing and buy a trawler"! Bob
Smoothness
Bob, when you go to put on the 3-blade and discover it's smoother than the old 2-blade, so you don't have an apples and oranges comparison, realize there are come things going on there besides just the number of blades. 1. New vs Old: The new 3-blade is NEW - has never hit a piece of debris and therefor will be in perfect true (well, kinda. depends on how good it was built to begin with but that's probably true). The old prop will no doubt be somewhat unbalanced from electrolysis. 2. Quality build of New vs Old: The old 2-blade was the cheapest one available meaning it had two blades and would push the boat. Whether the blades are exactly the same angle at the same distance from the centerline I would doubt it. A good trueing of the prop will check the angle. Ditto balancing the prop - the old one was probably not balanced. The new and I would presume better built prop (no prop is too good for your boat) will be better built and so should spin more evenly. 3. Distance from Prop to Hull: The diameter of the 3-blade will be slightly less than the old 2-blade so the distance from the prop tip to the hull will be less and therefor will, in and of itself, make things a tad smoother. The prop shop that sells you the new prop may suggest you bring in the prop shaft so they can check it for trueness. If the old prop ever hit anything there is a possiblity the taper was bent so - new shaft and ergo smoother running. Some suggestions for the project: Might want to replace the cutlass while everything is apart. A new cutlass will probably reduce vibration too. When the rudder goes back on, coat the nuts and bolts with Lanocoat to help prevent galvanic corrosion. No work on a boat goes smoothly! When you take the quadrant apart to drop the rudder the stainless bolts in the aluminum quadrant will probably break and need replacing. (Note: I'm assuming the C30 has an aluminum quadrant vice tiller and the bolts never had anti-sieze applied). Good time to check the pulleys on the helm too. Work - it's never ending! Have a good trip!
Bob, when you go to put on the 3-blade and discover it's smoother than the old 2-blade, so you don't have an apples and oranges comparison, realize there are come things going on there besides just the number of blades. 1. New vs Old: The new 3-blade is NEW - has never hit a piece of debris and therefor will be in perfect true (well, kinda. depends on how good it was built to begin with but that's probably true). The old prop will no doubt be somewhat unbalanced from electrolysis. 2. Quality build of New vs Old: The old 2-blade was the cheapest one available meaning it had two blades and would push the boat. Whether the blades are exactly the same angle at the same distance from the centerline I would doubt it. A good trueing of the prop will check the angle. Ditto balancing the prop - the old one was probably not balanced. The new and I would presume better built prop (no prop is too good for your boat) will be better built and so should spin more evenly. 3. Distance from Prop to Hull: The diameter of the 3-blade will be slightly less than the old 2-blade so the distance from the prop tip to the hull will be less and therefor will, in and of itself, make things a tad smoother. The prop shop that sells you the new prop may suggest you bring in the prop shaft so they can check it for trueness. If the old prop ever hit anything there is a possiblity the taper was bent so - new shaft and ergo smoother running. Some suggestions for the project: Might want to replace the cutlass while everything is apart. A new cutlass will probably reduce vibration too. When the rudder goes back on, coat the nuts and bolts with Lanocoat to help prevent galvanic corrosion. No work on a boat goes smoothly! When you take the quadrant apart to drop the rudder the stainless bolts in the aluminum quadrant will probably break and need replacing. (Note: I'm assuming the C30 has an aluminum quadrant vice tiller and the bolts never had anti-sieze applied). Good time to check the pulleys on the helm too. Work - it's never ending! Have a good trip!
Propeller Comparison
You will be much more comfortable with a three blade because you won't have that lump in you wallet where you money used to be. O Yeah, your boat won't motor any faster, it will sail slower and the prop wash in reverse will get worse. I'm amazed to see what folks think they need to buy. Must be some good prop salesmen out there. It may be worth getting the old fixed prop balanced but I'd draw the line there unless you have illegal income to dispose of
You will be much more comfortable with a three blade because you won't have that lump in you wallet where you money used to be. O Yeah, your boat won't motor any faster, it will sail slower and the prop wash in reverse will get worse. I'm amazed to see what folks think they need to buy. Must be some good prop salesmen out there. It may be worth getting the old fixed prop balanced but I'd draw the line there unless you have illegal income to dispose of
Bay prop rebuild
Reading John's comments reminded me of our prop improvement action. We pulled our two bladed OEM prop and sent it to Bay Prop in Alameda, CA. They cleaned it up, trued it, and bent the tips to form "winglets". The result was a real reduction in vibration, and about another half knot of speed in flat water. Since Lady Lillie has spent her life in fresh water, there were no corrosion effects. And the cost was around $150. David Lady Lillie
Reading John's comments reminded me of our prop improvement action. We pulled our two bladed OEM prop and sent it to Bay Prop in Alameda, CA. They cleaned it up, trued it, and bent the tips to form "winglets". The result was a real reduction in vibration, and about another half knot of speed in flat water. Since Lady Lillie has spent her life in fresh water, there were no corrosion effects. And the cost was around $150. David Lady Lillie
2 blade/3 blade prop Bob
Bob,just out if curisity let us know what you do and what you find the results to be and if you were satisifed.
Bob,just out if curisity let us know what you do and what you find the results to be and if you were satisifed.
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