I just got my new AutoProp installed on my 1992 37.5. Wow. This thing is kind of amazing. I do 4.5 knots @1000 5.5 knots @1500 6.5 @2000 RPM and max out around 2800 at the hull speed of 7.5 knots. I still have 3/4 of my throttle left and of course, once you hit hull speed, you get no more RPM's. Backing etc. is all that's advertised and I have to hit reverse hard coming into my slip now because it flies once I put it into neutral. Only one thing makes me nervous and the factory told me that it is common. I get a slight vibration and harmonic up to 1000 RPM and after 1000 RPM it picks up gradually until I get to 2500 RPM when it lessens again and is barely noticable after that and when I am going the hull speed. They assure me that this is normal. Have all the rest of you autoprop lovers run into the same thing? ChuckWolfe@innocent.com (Rhapsody)
- Status
- Not open for further replies.
L
Larry Long
If aftermarket props are really so much better than the ones supplied by the Hunter factory why doesn't Hunter change to the better prop? I look at the other components on my boat and see that Hunter seems to use high quality everywhere(Lewmar Ocean hatches, good two-speed self-tailing wenches, Force-10 stove, Autohelm instruments). Why would they use anything but the best prop for the job at hand?
D
Dakota Jim
Problems Brewing
I have the maxi-prop and get similar performance. Problem is that since I'm not maxed out at the max rated for the engine, I am probably have too high a pitch on the prop. Works fine until big waves. Then, I think, I'll have problems with the engine smoking and not getting where I want. Play to reduce the maxi by two degrees next year with a potential increase in rpms for the same speed, but maxing out at a higher rpm. Would like to see others reaction to my thoughts on this.
I have the maxi-prop and get similar performance. Problem is that since I'm not maxed out at the max rated for the engine, I am probably have too high a pitch on the prop. Works fine until big waves. Then, I think, I'll have problems with the engine smoking and not getting where I want. Play to reduce the maxi by two degrees next year with a potential increase in rpms for the same speed, but maxing out at a higher rpm. Would like to see others reaction to my thoughts on this.
B
Bob E.
Engine RPMs with AutoProp
I don't have any experience with this type of prop, but from your table of boat speed versus engine RPM and what I have read in many articles on this Web site about Yanmar diesels, your engine may be overloaded by this prop. This can lead to problems with carbon accumulation in the mixing elbow. Ideally, you should cruise at about 80% of maximum rated RPM, which is usually 2800-3000 RPM. Also, doesn't it make docking a little exciting if you idle at 4 knots?
I don't have any experience with this type of prop, but from your table of boat speed versus engine RPM and what I have read in many articles on this Web site about Yanmar diesels, your engine may be overloaded by this prop. This can lead to problems with carbon accumulation in the mixing elbow. Ideally, you should cruise at about 80% of maximum rated RPM, which is usually 2800-3000 RPM. Also, doesn't it make docking a little exciting if you idle at 4 knots?
P
Paul Bednarzyk
MaxProp
Chuck, I have a Maxprop on my 380. With it I can get 3600 rpm, but get about 7 to 7.5 kts at 3000 rpm. My experiance with backing into my slip is similar. In response to the question as to why it isn't standard equipment is probably because of the cost, $2000 vs. $200-300 for a standard two or three bladed prop. Paul Bednarzyk S/V Knot Again
Chuck, I have a Maxprop on my 380. With it I can get 3600 rpm, but get about 7 to 7.5 kts at 3000 rpm. My experiance with backing into my slip is similar. In response to the question as to why it isn't standard equipment is probably because of the cost, $2000 vs. $200-300 for a standard two or three bladed prop. Paul Bednarzyk S/V Knot Again
C
Chuck Wolfe
More about vibration
I'm thoroughly familiar with the difference between Max-Prop and Auto-Prop. I don't see how I'm overloading the engine to begin with. Once I hit hull speed, giving it more throttle doesn't increase the RPM's although I understand that it will in headseas. I can tie up at the dock, put it in gear and get 3450 RPM which is the rating for my engine. But because it pitches itself in according to torque, once you hit hull speed, you have maxed it out. My idle max RPM is also approx 3450. Meanwhile, no one talked about vibration. And it will only be exciting docking if my engine quits. Hitting reverse with any authority is like putting on brakes on my car. I got this prop because I have to motor quite often going to Catalina and this should be a godsend. The factory tells me that it's a fallacy that the engine overloads and I can tell you that at 2700 RPM, my throttle is about 25% less forward that before. It has to be using a lot less fuel for sure.
I'm thoroughly familiar with the difference between Max-Prop and Auto-Prop. I don't see how I'm overloading the engine to begin with. Once I hit hull speed, giving it more throttle doesn't increase the RPM's although I understand that it will in headseas. I can tie up at the dock, put it in gear and get 3450 RPM which is the rating for my engine. But because it pitches itself in according to torque, once you hit hull speed, you have maxed it out. My idle max RPM is also approx 3450. Meanwhile, no one talked about vibration. And it will only be exciting docking if my engine quits. Hitting reverse with any authority is like putting on brakes on my car. I got this prop because I have to motor quite often going to Catalina and this should be a godsend. The factory tells me that it's a fallacy that the engine overloads and I can tell you that at 2700 RPM, my throttle is about 25% less forward that before. It has to be using a lot less fuel for sure.
J
John
Agree with overloading
Some of the statements made are confusing. If the engine is the normally aspirated Yanmar and the boat reaches hull speed, 7.5 kts at 2800 and that is the maximum rpms, then it appears the engine is overloaded. The redline for the standard engine is 3600 which should be able to reach while under way, within plus or minus 50 rpm or so. Every Yanmar expert I have heard says that these engines like to turn at high rpm to prevent carbon buildup and by high rpm they're talking about anything in the realm of 3000, give or take, as a minimum cruise rpm. Decreasing the prop pitch would increase the maximum rpm capability. What were the rpm figures with the old prop? As for vibration, it would be helpful to know what the vibration was before the new prop was added. Zincs could be a factor. Speaking of vibration, last weekend I adjusted the valves on my 3GM30 ('88 with lots of hours) and found that the vibration was noticeably less. I should have checked the before clearance but it was definitely a lot more than 0.008 ins and judging by the feeler gauge slop it wouldn't surprise me if it was in the 0.010 ins range as the gauge was quite loose. My suspicion is that the vibration was caused by uneven valve clearance. A fringe benefit of the adjustment is the engine starts almost instantly now whereas before it required several revolutions before it would kick off. The reason Hunter doesn't use more expensive feathering props is simply because they cost significantly more (my opinion). A feathering/folding prop can also cause higher maintenance costs if the marina is "hot" or if the boat has electrolysis problems. Also, properly maintaining a feathering prop requires more technical expertise than the fixed blade variety.
Some of the statements made are confusing. If the engine is the normally aspirated Yanmar and the boat reaches hull speed, 7.5 kts at 2800 and that is the maximum rpms, then it appears the engine is overloaded. The redline for the standard engine is 3600 which should be able to reach while under way, within plus or minus 50 rpm or so. Every Yanmar expert I have heard says that these engines like to turn at high rpm to prevent carbon buildup and by high rpm they're talking about anything in the realm of 3000, give or take, as a minimum cruise rpm. Decreasing the prop pitch would increase the maximum rpm capability. What were the rpm figures with the old prop? As for vibration, it would be helpful to know what the vibration was before the new prop was added. Zincs could be a factor. Speaking of vibration, last weekend I adjusted the valves on my 3GM30 ('88 with lots of hours) and found that the vibration was noticeably less. I should have checked the before clearance but it was definitely a lot more than 0.008 ins and judging by the feeler gauge slop it wouldn't surprise me if it was in the 0.010 ins range as the gauge was quite loose. My suspicion is that the vibration was caused by uneven valve clearance. A fringe benefit of the adjustment is the engine starts almost instantly now whereas before it required several revolutions before it would kick off. The reason Hunter doesn't use more expensive feathering props is simply because they cost significantly more (my opinion). A feathering/folding prop can also cause higher maintenance costs if the marina is "hot" or if the boat has electrolysis problems. Also, properly maintaining a feathering prop requires more technical expertise than the fixed blade variety.
J
Justin Wolfe
John, Adjusting the valves?
Change of topics, but we are going to be adjusting the valves and torquing the head on our 3GM30 this weekend for the first time. Any suggestions on what to watch out for? Also, I had conflicting info on this. Do you torque the heads with the engine cold or warm? Do you adjust the valves with the engine cold or warm? Any comments appreciated.
Change of topics, but we are going to be adjusting the valves and torquing the head on our 3GM30 this weekend for the first time. Any suggestions on what to watch out for? Also, I had conflicting info on this. Do you torque the heads with the engine cold or warm? Do you adjust the valves with the engine cold or warm? Any comments appreciated.
R
Ron Johnson
Overloaded Yanmar
Equipped my H336 with a Maxiprop this season and also experience an increase in vibration when rpms are within the range of 2000-2600. Set the pitch to that speced by Hunter. Top rpm isn't much above 3000 which indicates the pitch is too great. Will reduce pitch 2 degrees next season. Original 2-blade fix prop was nearly vibration free so don't suspect alignment is the culpirt. How about the flex coupling distributed by PYI, anyone have experience with this item? Ron
Equipped my H336 with a Maxiprop this season and also experience an increase in vibration when rpms are within the range of 2000-2600. Set the pitch to that speced by Hunter. Top rpm isn't much above 3000 which indicates the pitch is too great. Will reduce pitch 2 degrees next season. Original 2-blade fix prop was nearly vibration free so don't suspect alignment is the culpirt. How about the flex coupling distributed by PYI, anyone have experience with this item? Ron
G
George Kornreich
No vibration
I have no vibration with my Autoprop, and if the factory tells you it's OK, I'd like to have them explain the source of the vibration before I'd feel comfortable with it. Did they? Enginology 101: (If you're an airplane driver you already know this stuff and can skip ahead to GO.) Fuel consumption is a complex factor, but roughly, for any engine, the fuel consumption is a function of horsepower produced. Considering that your driving a complex prop, for the SAME horsepower, the lower the RPM (and therefore the higher the cylinder loading and manifold vacuum, the lower the fuel consumption, as lower RPM translates into lower friction or lower total work. But this must be maintained within allowable specs for any engine. TOO low an RPM, and therefore too high a throttle setting, will blow apart the engine, either gradually, or castrophically. On the other hand, and there is usually an other hand in most things in life, Diesels thrive on working hard, and they do this best by higher RPM rather than lugging. Compromises, right? In a non-fuel injected gasoline engine, the throttle controls the AIR intake, and the fuel is just sucked along for the ride, its only control being the mixture valve (and nowadays in a car, the emissions computer). With a fuel injector (Diesel or gas), throttle controls fuel flow at the injector and the air sort of takes care of itself. In the airplane the fuel/air mixture is usually manually controlled, but I haven't seen a boat yet with a mixture control. What we really need is power output charts for our engines, throttle (manifold pressure) vs rpm, and showing the allowable combinations. If you find this, let me know, 'cause I'll be right there to grab a copy. The Autoprop sets its RPM as a balance of centrifigal force and hydrodynamic loading on the blades. Nice idea, but is the pitch obtained really the ideal pitch for that particular RPM? Don't know, and haven't seen that explained by Autoprop. Seems the pitch will be a function of prop size, all else equal. They talk about reaching hull speed at lower RPM. That means higher engine loading (and better fuel economy), but we still don't know if the pitch is the one we'd choose if we could manually at any moment, or if we are loading the engine "outside the envelope".
I have no vibration with my Autoprop, and if the factory tells you it's OK, I'd like to have them explain the source of the vibration before I'd feel comfortable with it. Did they? Enginology 101: (If you're an airplane driver you already know this stuff and can skip ahead to GO.) Fuel consumption is a complex factor, but roughly, for any engine, the fuel consumption is a function of horsepower produced. Considering that your driving a complex prop, for the SAME horsepower, the lower the RPM (and therefore the higher the cylinder loading and manifold vacuum, the lower the fuel consumption, as lower RPM translates into lower friction or lower total work. But this must be maintained within allowable specs for any engine. TOO low an RPM, and therefore too high a throttle setting, will blow apart the engine, either gradually, or castrophically. On the other hand, and there is usually an other hand in most things in life, Diesels thrive on working hard, and they do this best by higher RPM rather than lugging. Compromises, right? In a non-fuel injected gasoline engine, the throttle controls the AIR intake, and the fuel is just sucked along for the ride, its only control being the mixture valve (and nowadays in a car, the emissions computer). With a fuel injector (Diesel or gas), throttle controls fuel flow at the injector and the air sort of takes care of itself. In the airplane the fuel/air mixture is usually manually controlled, but I haven't seen a boat yet with a mixture control. What we really need is power output charts for our engines, throttle (manifold pressure) vs rpm, and showing the allowable combinations. If you find this, let me know, 'cause I'll be right there to grab a copy. The Autoprop sets its RPM as a balance of centrifigal force and hydrodynamic loading on the blades. Nice idea, but is the pitch obtained really the ideal pitch for that particular RPM? Don't know, and haven't seen that explained by Autoprop. Seems the pitch will be a function of prop size, all else equal. They talk about reaching hull speed at lower RPM. That means higher engine loading (and better fuel economy), but we still don't know if the pitch is the one we'd choose if we could manually at any moment, or if we are loading the engine "outside the envelope".
C
Chuck Vincent
I had it to, Vibration Not Good.
I had a very smooth engine drive train on my 1993 Passage 42. I had been considering making a change to the Auto-Prop or the Max-Prop. In February of this year, we went to the Miami Boat Show. There I had the opportunity to talk to both Auto-Prop, and Max-Prop. I was very attracted to the speed and power of the Auto-Prop, and the fact that it was suppose to be a straight bolt on, and made the purchase in the month of March. Many problems from the start, because it was not a straight bolt on, I had to add a “Drive Saver” to add an inch of clearance to the strut so the prop would clear. When I finally got to test the prop, I though the whole drive train would vibrate apart. It would start to get real bad around (2500 RPM), and was so bad from (2900 to 3200) I was scared I would tear something apart. We hauled the boat again, and discovered that blade angle and track appeared to be slightly off, and believed also that the prop was out of balance, but had no way of checking balance. We then check the drive aliment at the coupler and found less than (.0004). Knowing that before I bolted the Auto-Prop on I had a very smooth drive train, something was very wrong. In addition, I was turning up too much RPM (3900), and it should max out at (3600). I contacted Auto-Prop again, and I must add that throughout all three (3) props we tried from Auto-Prop, Steve and the office were very nice and tried to be helpful and supportive. They sent me another prop that we installed. It too vibrated although slightly less and at a different point. We hauled the boat again, after being sent a third prop with much discussing with Steve at Auto-Prop. We believed that this Prop would be correct. So we blindly bolted it on, and dropped the boat in the water. Slightly different vibration, but very much still there. We were instructed to put the boat in forward gear, then shut the engine down and remove the drive saver. Vibration was less, but still there. Upon haul out, we checked blade angle and track, and discovered a small difference on prop three also. I was very disappointed. After four haul out, three different Auto-Props, I gave up. I know this is going to sound like an ad for Max-Prop, but that’s what I went to. We pulled the Auto-Prop, and installed the Max-Prop, and we are back to a very smooth drive train. I do miss the power and extra speed of the Auto-Prop, but the vibration would have tore the boat apart eventually, not to mention the sheer aggravation. Their props must work correctly on some boats, because if they didn’t they would be out of business. Also, I would like to say again, that the people at Auto-Prop were very courteous, and tried to help in every way. It just didn’t work for me. Chuck
I had a very smooth engine drive train on my 1993 Passage 42. I had been considering making a change to the Auto-Prop or the Max-Prop. In February of this year, we went to the Miami Boat Show. There I had the opportunity to talk to both Auto-Prop, and Max-Prop. I was very attracted to the speed and power of the Auto-Prop, and the fact that it was suppose to be a straight bolt on, and made the purchase in the month of March. Many problems from the start, because it was not a straight bolt on, I had to add a “Drive Saver” to add an inch of clearance to the strut so the prop would clear. When I finally got to test the prop, I though the whole drive train would vibrate apart. It would start to get real bad around (2500 RPM), and was so bad from (2900 to 3200) I was scared I would tear something apart. We hauled the boat again, and discovered that blade angle and track appeared to be slightly off, and believed also that the prop was out of balance, but had no way of checking balance. We then check the drive aliment at the coupler and found less than (.0004). Knowing that before I bolted the Auto-Prop on I had a very smooth drive train, something was very wrong. In addition, I was turning up too much RPM (3900), and it should max out at (3600). I contacted Auto-Prop again, and I must add that throughout all three (3) props we tried from Auto-Prop, Steve and the office were very nice and tried to be helpful and supportive. They sent me another prop that we installed. It too vibrated although slightly less and at a different point. We hauled the boat again, after being sent a third prop with much discussing with Steve at Auto-Prop. We believed that this Prop would be correct. So we blindly bolted it on, and dropped the boat in the water. Slightly different vibration, but very much still there. We were instructed to put the boat in forward gear, then shut the engine down and remove the drive saver. Vibration was less, but still there. Upon haul out, we checked blade angle and track, and discovered a small difference on prop three also. I was very disappointed. After four haul out, three different Auto-Props, I gave up. I know this is going to sound like an ad for Max-Prop, but that’s what I went to. We pulled the Auto-Prop, and installed the Max-Prop, and we are back to a very smooth drive train. I do miss the power and extra speed of the Auto-Prop, but the vibration would have tore the boat apart eventually, not to mention the sheer aggravation. Their props must work correctly on some boats, because if they didn’t they would be out of business. Also, I would like to say again, that the people at Auto-Prop were very courteous, and tried to help in every way. It just didn’t work for me. Chuck
J
John
Shaft May Be a Factor
Our '88 Hunter 35 came with a 1-inch bronze shaft as standard equipment. To install the new prop I had a new shaft made to match the prop taper prior to hauling the boat in order to minimize lay days at the haul-out facility. It was unknown what the existing taper was on the OEM shaft and the prop distance from the strut was unknown. The new shaft was stainless because this was what the machine shop highly recommended. Once the old shaft was removed the new one was machined to length and the keyway installed. Later, due to a discussion with another Hunter owner who had a 37 (or 37.5) on the subject of vibration, he did some calculations on bronze vs stainless and we found that the bronze shaft for the 37 was just marginal for the required prop shaft length. A stainless shaft provides about 25 percent greater stiffness than bronze and therefore would produce less vibration, everything else being equal. Just another factor to consider in the holistic approach to vibration reduction.
Our '88 Hunter 35 came with a 1-inch bronze shaft as standard equipment. To install the new prop I had a new shaft made to match the prop taper prior to hauling the boat in order to minimize lay days at the haul-out facility. It was unknown what the existing taper was on the OEM shaft and the prop distance from the strut was unknown. The new shaft was stainless because this was what the machine shop highly recommended. Once the old shaft was removed the new one was machined to length and the keyway installed. Later, due to a discussion with another Hunter owner who had a 37 (or 37.5) on the subject of vibration, he did some calculations on bronze vs stainless and we found that the bronze shaft for the 37 was just marginal for the required prop shaft length. A stainless shaft provides about 25 percent greater stiffness than bronze and therefore would produce less vibration, everything else being equal. Just another factor to consider in the holistic approach to vibration reduction.
J
John
Adjisting Valves
Topic within a topic! The shop manual says to adjust the valves with the engine cold. Valve clearance is 0.0079 inches, or, rounded to 0.008. Adjustment takes a stubby flat-blade screwdriver and a 10mm wrench; box prefered. Valve cover also takes a 10 mm wrench. Dont loose any of the little neoprene washers on the valve cover bolts - I almost did. Valve cover has a reuseable o-ring gasket but on my ten year old engine I wish I had bought a new one. When adjusting the valves the procedure is to loosen the lock nut and adjust the slotted center screw to the measured amount and then tighten the lock nut. On my engine the center screw was not a snug fit in the rocker and as the nut was tightened the nut caused the screw to want to turn. The problem is the screwdriver tip had some slop in the slot and it was very difficult to keep the setting from changing. I used the compression release levers to help pop the valve cover off. It was 'glued' on pretty tight. Remember to return the levers to the run position right after remiving the cover. The pitch on the center screw works out so 58-degrees of a turn equals the 0.0078-inch gap setting so it is possible to set the adjustment without a feeler gauge. What this means, however, is that a very small rotation of the screw accounts for a large change in the clearance. Try to have a screwdriver with a wider tip than the average. It may be worth getting a cheap screwdriver and grinding the tip just to get a snug fit, this would help. I had to adjust and tighten several times in order to get one rocker arm to be close to the proper clearance. If you do your own work like this you probably already know, but for the benifit of others, it is important to have the valve clearance uniform for a smooth running engine. But then for a diesel this may be an oxymoron. Head bolts: I don't know but my guess is this would be done cold also. I should have done these also but .... maybe next time. Shop manual: this is a good thing to have. Power curves, fuel burn curves, etc. are all there for each model. Head bolt tightening pattern is in there too.
Topic within a topic! The shop manual says to adjust the valves with the engine cold. Valve clearance is 0.0079 inches, or, rounded to 0.008. Adjustment takes a stubby flat-blade screwdriver and a 10mm wrench; box prefered. Valve cover also takes a 10 mm wrench. Dont loose any of the little neoprene washers on the valve cover bolts - I almost did. Valve cover has a reuseable o-ring gasket but on my ten year old engine I wish I had bought a new one. When adjusting the valves the procedure is to loosen the lock nut and adjust the slotted center screw to the measured amount and then tighten the lock nut. On my engine the center screw was not a snug fit in the rocker and as the nut was tightened the nut caused the screw to want to turn. The problem is the screwdriver tip had some slop in the slot and it was very difficult to keep the setting from changing. I used the compression release levers to help pop the valve cover off. It was 'glued' on pretty tight. Remember to return the levers to the run position right after remiving the cover. The pitch on the center screw works out so 58-degrees of a turn equals the 0.0078-inch gap setting so it is possible to set the adjustment without a feeler gauge. What this means, however, is that a very small rotation of the screw accounts for a large change in the clearance. Try to have a screwdriver with a wider tip than the average. It may be worth getting a cheap screwdriver and grinding the tip just to get a snug fit, this would help. I had to adjust and tighten several times in order to get one rocker arm to be close to the proper clearance. If you do your own work like this you probably already know, but for the benifit of others, it is important to have the valve clearance uniform for a smooth running engine. But then for a diesel this may be an oxymoron. Head bolts: I don't know but my guess is this would be done cold also. I should have done these also but .... maybe next time. Shop manual: this is a good thing to have. Power curves, fuel burn curves, etc. are all there for each model. Head bolt tightening pattern is in there too.
C
Chuck Wolfe
Autoprop-& Max RPM's
Those of you who don't have Autoprops are missing some info. This prop pitches itself based on torque etc. If I tie my boat down to the dock and put my engine in gear (My Max RPM's on engine is 3450) I can get the engine up to 3425 RPM's. Once you hit the hull speed, giving more fuel dosnn't increase RPM's. Autoprop tells me that I will get more RPM's in headseas and less in following seas to reach hull speed. I talked to Yanmar and they tell me that so long as the engine doesn't belch out black smoke, I am not overloading it. End of story. They have heard of Autoprop but don't have any particular feedback. I will take my boat out this week, get it to hull speed downwind and watch the exhaust. I will then push the throttle forward after I reach hull speed to see if I can get some black smoke because Yanmar says I should do this for 10 or 15 minutes every month. I'll let everyone know.
Those of you who don't have Autoprops are missing some info. This prop pitches itself based on torque etc. If I tie my boat down to the dock and put my engine in gear (My Max RPM's on engine is 3450) I can get the engine up to 3425 RPM's. Once you hit the hull speed, giving more fuel dosnn't increase RPM's. Autoprop tells me that I will get more RPM's in headseas and less in following seas to reach hull speed. I talked to Yanmar and they tell me that so long as the engine doesn't belch out black smoke, I am not overloading it. End of story. They have heard of Autoprop but don't have any particular feedback. I will take my boat out this week, get it to hull speed downwind and watch the exhaust. I will then push the throttle forward after I reach hull speed to see if I can get some black smoke because Yanmar says I should do this for 10 or 15 minutes every month. I'll let everyone know.
- Status
- Not open for further replies.