Under full power, my M25 XPB turns 3200 rpm. Universal said to increase the pitch 1 degree to get it to 3000 rpm wide open. Has any one else experienced this and when you re-pitched did you experience any increase in cruise speed? We currently cruise at 6kts @ 2500 rpm. I am also considering a three blade prop. What kinds of cruise speed are you seeing with a 3 blade? Up here in the Northwest you spend alot of time motoring and in many cases with strong currents so speed is important. Thanks Jeff
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Make sure your tach is calibrated
Mine was way off from the factory. I purchased a unit at my local auto parts store to check rpm's You basically put a reflective sticker on the crank shaft pulley, aim the strobe at it and it will tell you accurately what rpm the motor is turning. My guess is the prop from the factory is right but your tach is not... Depending on current I can motor between 5.8 and 6.4 with the factory three blade. -Rodd C.
Mine was way off from the factory. I purchased a unit at my local auto parts store to check rpm's You basically put a reflective sticker on the crank shaft pulley, aim the strobe at it and it will tell you accurately what rpm the motor is turning. My guess is the prop from the factory is right but your tach is not... Depending on current I can motor between 5.8 and 6.4 with the factory three blade. -Rodd C.
Prop Tach
I have had the tach checked by two different maintenance services and they said that the tach was dead on with the engine. I can only assume that if I add pitch to the prop I will gain at least a little extra thrust. Jeff
I have had the tach checked by two different maintenance services and they said that the tach was dead on with the engine. I can only assume that if I add pitch to the prop I will gain at least a little extra thrust. Jeff
Not an expert
Jeff, as stated, I am not an expert, but I have a little knowledge that I will throw in. Perhaps you will get a real expert to answer your question, that's what's great about this board. Generally speaking, an engine is supposed to turn a certain RMP at max throttle, and that can be adjusted, determined by the prop that you use. There are always sacrifices, in one direction or another,regarding prop selection. To maximize speed under sail, you would use a folding prop. Generally speaking, a three blade prop will deliver more power and thrust, but add some drag under sail and slow the boat a bit. If you have to motor a good bit, and sail for fun and pleasure, and do not race, you might do better with a properly pitched three blade prop, as you have described your situation. Of course, I am open to being corrected by a real expert, but then, amazingly, another expert may appear who has a different opinion. I have an old saying for that. "Experts disagree." In the end, if you motor a good bit, and it is important to have good control and speed under motor, I'd go with a properly pitched three blade prop. Hope it all works out well for you.
Jeff, as stated, I am not an expert, but I have a little knowledge that I will throw in. Perhaps you will get a real expert to answer your question, that's what's great about this board. Generally speaking, an engine is supposed to turn a certain RMP at max throttle, and that can be adjusted, determined by the prop that you use. There are always sacrifices, in one direction or another,regarding prop selection. To maximize speed under sail, you would use a folding prop. Generally speaking, a three blade prop will deliver more power and thrust, but add some drag under sail and slow the boat a bit. If you have to motor a good bit, and sail for fun and pleasure, and do not race, you might do better with a properly pitched three blade prop, as you have described your situation. Of course, I am open to being corrected by a real expert, but then, amazingly, another expert may appear who has a different opinion. I have an old saying for that. "Experts disagree." In the end, if you motor a good bit, and it is important to have good control and speed under motor, I'd go with a properly pitched three blade prop. Hope it all works out well for you.
Different type prop
Our C310 is a different situation, but it's the only situation I have experience with. We cruise at 6.5-6.8 knots in flat water. And that's at 1800 RPM. That would normally indicate an extremely over-pitched prop. Ours though is a three blade, feathering, self-pitching Autoprop. Attaining hull speed at only 1800 RPM shows that the M25 has plenty of power. Anything over 1800 RPM causes excessive engine loading and black smoke, and of course we can't exceed hull speed in any case. When we encounter heavy chop or headwinds and our speed begins to drop, the Autoprop automatically decreases pitch, allowing the rev's to increase per knot of boat speed. When applying power from a dead stop, the pitch is also reduced until the boat gets up to speed. Kind of functions like an overdrive gear on a car. I have discussed this with the US Autoprop people, and they assure me that all this is all normal. As long as we're not blowing black smoke I don't think we're overloading the engine. BTW, we had the first Autoprop changed out right after commissioning for the current one, which is 3/4 inch smaller diameter. The first one was OK except that we were doing 4 knots at idle. Kind of made docking exciting!
Our C310 is a different situation, but it's the only situation I have experience with. We cruise at 6.5-6.8 knots in flat water. And that's at 1800 RPM. That would normally indicate an extremely over-pitched prop. Ours though is a three blade, feathering, self-pitching Autoprop. Attaining hull speed at only 1800 RPM shows that the M25 has plenty of power. Anything over 1800 RPM causes excessive engine loading and black smoke, and of course we can't exceed hull speed in any case. When we encounter heavy chop or headwinds and our speed begins to drop, the Autoprop automatically decreases pitch, allowing the rev's to increase per knot of boat speed. When applying power from a dead stop, the pitch is also reduced until the boat gets up to speed. Kind of functions like an overdrive gear on a car. I have discussed this with the US Autoprop people, and they assure me that all this is all normal. As long as we're not blowing black smoke I don't think we're overloading the engine. BTW, we had the first Autoprop changed out right after commissioning for the current one, which is 3/4 inch smaller diameter. The first one was OK except that we were doing 4 knots at idle. Kind of made docking exciting!
To the C-310 with the Auto Prop
If you are doing hull speed at 1800 rpm then you are overloading the engine! If you can't get the motor to turn 3000-3200 at full throttle the engine is overloaded. The black smoke you discuss when going above 1800 means that the engine is up against to much prop! I would check and see of there are any ways to manually adjust the pitch to match you engine or your going to have a hefty repair bill on your hands soon. Trust me I had this same problem on my C-30 years ago and it eventually cost me the engine! The auto props campaign of "self pitching" is just that a campaign. I know more sailors that have been sold this bill of goods and comeup 2 grand short because of it. You have to ask yourself one question.. Does it auto pitch to my engine or my hull?????? Just because you don't see black smoke at 1800 rpm does not mean the engine is not overloaded.. Have this checked out soon or you'll plug your exhast elbow, overheat your engine and well you know the rest... You wrote..... Our C310 is a different situation, but it's the only situation I have experience with. We cruise at 6.5-6.8 knots in flat water. And that's at 1800 RPM. That would normally indicate an extremely over-pitched prop. Ours though is a three blade, feathering, self-pitching Autoprop. Attaining hull speed at only 1800 RPM shows that the M25 has plenty of power. Anything over 1800 RPM causes excessive engine loading and black smoke, and of course we can't exceed hull speed in any case.
If you are doing hull speed at 1800 rpm then you are overloading the engine! If you can't get the motor to turn 3000-3200 at full throttle the engine is overloaded. The black smoke you discuss when going above 1800 means that the engine is up against to much prop! I would check and see of there are any ways to manually adjust the pitch to match you engine or your going to have a hefty repair bill on your hands soon. Trust me I had this same problem on my C-30 years ago and it eventually cost me the engine! The auto props campaign of "self pitching" is just that a campaign. I know more sailors that have been sold this bill of goods and comeup 2 grand short because of it. You have to ask yourself one question.. Does it auto pitch to my engine or my hull?????? Just because you don't see black smoke at 1800 rpm does not mean the engine is not overloaded.. Have this checked out soon or you'll plug your exhast elbow, overheat your engine and well you know the rest... You wrote..... Our C310 is a different situation, but it's the only situation I have experience with. We cruise at 6.5-6.8 knots in flat water. And that's at 1800 RPM. That would normally indicate an extremely over-pitched prop. Ours though is a three blade, feathering, self-pitching Autoprop. Attaining hull speed at only 1800 RPM shows that the M25 has plenty of power. Anything over 1800 RPM causes excessive engine loading and black smoke, and of course we can't exceed hull speed in any case.
I Re-Pitched
Jeff, I just recently had my 3 blade Campbell Sailor Prop re-pitched by the builders. I have a '77 C30 which I have repowered with a Yanmar 2GM (13HP)and the prop that was recommended was a 13x9 which I put on. Performance was to say the least poor with 4 knots cruise at 2900 RPM and at max 3600 I was getting about 4 3/4 knots. Poor performance in reverse. I had them change the pitch to 11 inch and recup the edge a bit. WOW! Total different boat. At 3000 RPM I am at 5 1/2 knots cruise and at the now max 3300 I am just over 6 knots. In reverse I believe I could haul the pilings out of the dock!!! The combination of size and pitch that I have now is not what should work but it sure does. Cliff Carter PlusOne C30 #598 Oak Bay, B.C.
Jeff, I just recently had my 3 blade Campbell Sailor Prop re-pitched by the builders. I have a '77 C30 which I have repowered with a Yanmar 2GM (13HP)and the prop that was recommended was a 13x9 which I put on. Performance was to say the least poor with 4 knots cruise at 2900 RPM and at max 3600 I was getting about 4 3/4 knots. Poor performance in reverse. I had them change the pitch to 11 inch and recup the edge a bit. WOW! Total different boat. At 3000 RPM I am at 5 1/2 knots cruise and at the now max 3300 I am just over 6 knots. In reverse I believe I could haul the pilings out of the dock!!! The combination of size and pitch that I have now is not what should work but it sure does. Cliff Carter PlusOne C30 #598 Oak Bay, B.C.
Autoprop opinions
Rodd, I don't know if you had an Autoprop on your C30 or not. The opinion that the Autoprop is overloading the engine if it doesn't reach full rpm is a popular one, but I don't see the logic myself. The M25 XPB makes 26 HP at 3000 rpm. At 1800 rpm it's putting out about 18 HP. It's obvious the C310 doesn't take 26 HP to achieve hull speed in flat water. The term overloading implies excessive load. Unless I try to push past hull speed, I don't see how this is overloading the engine. Torque reaches maximum at 47 lbs-ft at 2440 rpm. It's about 45 lbs-ft at 1800. Is running a standard engine and prop at low rpms when slowing to approach the dock considered overloading the engine? I don't think so because the engine output is appropriate to the load. It seems kind of like a car engine when you try to climb a hill in the top gear at low rpm. Now that’s overloading (lugging) the engine. But cruising down the freeway at 1600 rpm in the same gear is not overloading. The Autoprop will reduce pitch in adverse conditions or for example when towing another boat. Sort of like a car shifting down on a hill. Because I don't try to exceed hull speed I have no smoke. In this situation, I'm not clear on what substance is going to clog up the exhaust elbow. I have 400+ hours on the engine. Cooling temperature is steady at 165, and it purrs like a kitten, showing no sign of strain. The Autoprop does require a different mindset. I guess I'll disagree with traditional thinking based on traditional props, until my engine dies. I appreciate your opinions nonetheless.
Rodd, I don't know if you had an Autoprop on your C30 or not. The opinion that the Autoprop is overloading the engine if it doesn't reach full rpm is a popular one, but I don't see the logic myself. The M25 XPB makes 26 HP at 3000 rpm. At 1800 rpm it's putting out about 18 HP. It's obvious the C310 doesn't take 26 HP to achieve hull speed in flat water. The term overloading implies excessive load. Unless I try to push past hull speed, I don't see how this is overloading the engine. Torque reaches maximum at 47 lbs-ft at 2440 rpm. It's about 45 lbs-ft at 1800. Is running a standard engine and prop at low rpms when slowing to approach the dock considered overloading the engine? I don't think so because the engine output is appropriate to the load. It seems kind of like a car engine when you try to climb a hill in the top gear at low rpm. Now that’s overloading (lugging) the engine. But cruising down the freeway at 1600 rpm in the same gear is not overloading. The Autoprop will reduce pitch in adverse conditions or for example when towing another boat. Sort of like a car shifting down on a hill. Because I don't try to exceed hull speed I have no smoke. In this situation, I'm not clear on what substance is going to clog up the exhaust elbow. I have 400+ hours on the engine. Cooling temperature is steady at 165, and it purrs like a kitten, showing no sign of strain. The Autoprop does require a different mindset. I guess I'll disagree with traditional thinking based on traditional props, until my engine dies. I appreciate your opinions nonetheless.
Autoprop
Thank you all for your input thus far. Jon, I find your results very interesting. Where did you get your Autoprop and exactly what size are you using now. I want to avoid docking at 4 knots as well. Thanks
Thank you all for your input thus far. Jon, I find your results very interesting. Where did you get your Autoprop and exactly what size are you using now. I want to avoid docking at 4 knots as well. Thanks
Yes I did have an Auto Prop on my C-30
I did have an auto prop and the engine was brand new when the prop was installed a Universal M320B. Everyone kept trying to justify why it was okay that I could not turn full rpm even though I could reach theoretical hull speed. The engine always ran fine until it quit. When they went to rebuild it at 620 hours they said it looked like it had 6000 hours on it. I change my oil every 50 hours and even do a double flush meaning change oil and filter, run it a few minutes and change again. The only thing they could attribute to my engines demise was the auto prop. I switched back to a standard three blade (with no discernable difference in sailing performance) and the engine is still going after 7 years.....
I did have an auto prop and the engine was brand new when the prop was installed a Universal M320B. Everyone kept trying to justify why it was okay that I could not turn full rpm even though I could reach theoretical hull speed. The engine always ran fine until it quit. When they went to rebuild it at 620 hours they said it looked like it had 6000 hours on it. I change my oil every 50 hours and even do a double flush meaning change oil and filter, run it a few minutes and change again. The only thing they could attribute to my engines demise was the auto prop. I switched back to a standard three blade (with no discernable difference in sailing performance) and the engine is still going after 7 years.....
Rod, Jeff
First, Rod, I respect your experience with the Autoprop. Thanks for the expanded information. At this point though, I need to carry on and hope that your case was some type of an anomaly. Jeff, I don't know where my dealer (Admiralty Yachts) bought the prop. It was installed during commissioning. I also don't know the diameter. The Autoprop guys just told me that the replacement was point something inches less. Their props are custom specified for each application, boat, engine, gear ratio, and so on. Each prop is serialized, and they maintain a record of each prop and application. Your best bet is to contact them directly (see link). They seemed very helpful. If you do contact them, see if they will confirm that low cruising rpm is normal, like they did with me, and let us know. Be forewarned, these props are not inexpensive. P.S. If you're in the Everret marina, I may have seen your boat a week or so ago. I was walking the dog, when I saw a C310 visiting the fuel dock around noon in very challenging crosswind and current conditions.
First, Rod, I respect your experience with the Autoprop. Thanks for the expanded information. At this point though, I need to carry on and hope that your case was some type of an anomaly. Jeff, I don't know where my dealer (Admiralty Yachts) bought the prop. It was installed during commissioning. I also don't know the diameter. The Autoprop guys just told me that the replacement was point something inches less. Their props are custom specified for each application, boat, engine, gear ratio, and so on. Each prop is serialized, and they maintain a record of each prop and application. Your best bet is to contact them directly (see link). They seemed very helpful. If you do contact them, see if they will confirm that low cruising rpm is normal, like they did with me, and let us know. Be forewarned, these props are not inexpensive. P.S. If you're in the Everret marina, I may have seen your boat a week or so ago. I was walking the dog, when I saw a C310 visiting the fuel dock around noon in very challenging crosswind and current conditions.
Crosswind
Yes...that was me. Docking at the fuel dock in Everett in a stiff breeze and a -3.7 ft tide is difficult at best. The river runs a good 2knots in those conditions. I will get in touch with Autoprop as well as Admiralty as they were my broker as well. As far as rpm's go, I have a call into Universal to get the factories perspective. I will let you all know what I hear. Jeff
Yes...that was me. Docking at the fuel dock in Everett in a stiff breeze and a -3.7 ft tide is difficult at best. The river runs a good 2knots in those conditions. I will get in touch with Autoprop as well as Admiralty as they were my broker as well. As far as rpm's go, I have a call into Universal to get the factories perspective. I will let you all know what I hear. Jeff
Three Blade Crusing Prop from factory
Just for information. I opted for the three blade cruising prop from Catalina and it arrived fully installed when the boat was delivered to my dealer from the factory. I race sometimes and really don't notice a great deal of excess drag, and I really like the added maneuverability. I cruise at 2200-2600 RPM and that normally gets to around 5.5-6.5 knots depending on wind and waves-I sail on a Inland lake so swells are nonexistent. At 3000-3200 RPM I get to Hull speed. 6.9-7.1
Just for information. I opted for the three blade cruising prop from Catalina and it arrived fully installed when the boat was delivered to my dealer from the factory. I race sometimes and really don't notice a great deal of excess drag, and I really like the added maneuverability. I cruise at 2200-2600 RPM and that normally gets to around 5.5-6.5 knots depending on wind and waves-I sail on a Inland lake so swells are nonexistent. At 3000-3200 RPM I get to Hull speed. 6.9-7.1
I also had the factory installed 3 blade prop...
added to our 310, and it works pretty much the same as Ken described. I have not noticed a lot of drag associated with the fixed 3 blade, but, normally, I am also sailing on a very choppy lake (Lake Erie). Somewhere down the road, I may go with a feathering prop....need to research it a bit more...
added to our 310, and it works pretty much the same as Ken described. I have not noticed a lot of drag associated with the fixed 3 blade, but, normally, I am also sailing on a very choppy lake (Lake Erie). Somewhere down the road, I may go with a feathering prop....need to research it a bit more...
A word from Universal
I spoke with Gallery Marine in Seattle who is THE Westerbeke/Universal dealer in the area. They said that max rpm under load should be 3000rpm. I am turning 3125 so they said I should add one degree more of pitch from a 15x10 to a 15x11. I talked with a factory rep from Universal and he confirmed this information. He also stated that the optimum cruise rpm for the M25XPB is 80% of max or 2400rpm. I am going to go with a fixed three blade. Probably 15x10 but I need to work that out. I can't justify the $2000 for a MaxProp. I do not race and I have learned how to deal with prop walk. Neither gentleman could understand the 1800rpm Autoprop. A great guy to talk to is Irvine at Gallery Marine. Thought I pass on what I heard. Cheers
I spoke with Gallery Marine in Seattle who is THE Westerbeke/Universal dealer in the area. They said that max rpm under load should be 3000rpm. I am turning 3125 so they said I should add one degree more of pitch from a 15x10 to a 15x11. I talked with a factory rep from Universal and he confirmed this information. He also stated that the optimum cruise rpm for the M25XPB is 80% of max or 2400rpm. I am going to go with a fixed three blade. Probably 15x10 but I need to work that out. I can't justify the $2000 for a MaxProp. I do not race and I have learned how to deal with prop walk. Neither gentleman could understand the 1800rpm Autoprop. A great guy to talk to is Irvine at Gallery Marine. Thought I pass on what I heard. Cheers
Autoprop
I just can't help but jump in here about the Autoprop. I would agree with Rodd in that if you cannot reach rated max RPM at full throttle then the boat is overpropped period. This would apply to the Autoprop, Flexofold, MaxProp, any feathering or folding prop, 2 or 3 blade fixed, any prop. Diesels should be run, as one poster said, at 80% of max rpm. That being said, I have an Autoprop on my C-42. I can assure you that Autoprop marketing not a "campaign". The prop works and I can achieve full rated rpm on my 50hp Yanmar 4JH2E. It has lower drag under sail as evidenced by a recent cruise with 2 other C-42s: one equiped with a Flexofold, one with the factory 3 blade, and mine. We started out together and at the end, the Flexofold equiped C-42 was 3 boat lengths ahead of me and the fixed prop equiped C-42 was over a mile back. Yes, all of us were racing. I get 7.4 knots of boat speed in flat water at 2500 rpm (I usually cruise at 2800 rpm...80%). The Flexofold equiped C-42 needs 300 more rpm to go the same speed. Motorsailing is also a dream. Also prop walk in reverse is almost non-existant. IMHO the Autoprop lives up to the hype. BTW, I did not buy the Autoprop, it was on the boat when I purchased it and I was somewhat skeptical. Perhaps there are scale factors at work here. Rodney S/V Sashay C-42 #567 SF Bay
I just can't help but jump in here about the Autoprop. I would agree with Rodd in that if you cannot reach rated max RPM at full throttle then the boat is overpropped period. This would apply to the Autoprop, Flexofold, MaxProp, any feathering or folding prop, 2 or 3 blade fixed, any prop. Diesels should be run, as one poster said, at 80% of max rpm. That being said, I have an Autoprop on my C-42. I can assure you that Autoprop marketing not a "campaign". The prop works and I can achieve full rated rpm on my 50hp Yanmar 4JH2E. It has lower drag under sail as evidenced by a recent cruise with 2 other C-42s: one equiped with a Flexofold, one with the factory 3 blade, and mine. We started out together and at the end, the Flexofold equiped C-42 was 3 boat lengths ahead of me and the fixed prop equiped C-42 was over a mile back. Yes, all of us were racing. I get 7.4 knots of boat speed in flat water at 2500 rpm (I usually cruise at 2800 rpm...80%). The Flexofold equiped C-42 needs 300 more rpm to go the same speed. Motorsailing is also a dream. Also prop walk in reverse is almost non-existant. IMHO the Autoprop lives up to the hype. BTW, I did not buy the Autoprop, it was on the boat when I purchased it and I was somewhat skeptical. Perhaps there are scale factors at work here. Rodney S/V Sashay C-42 #567 SF Bay
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