Topics

[Amel Yacht Owners] Re: Props and rpm

 

Bill,

Excellent analysis! Clear, concise, accurate and very logical. Thanks, this is a gentle of a posting!

Best,

CW Bill Rouse
Admiral, Texas Navy
Commander Emeritus
Amel School www.amelschool.com
720 Winnie St
Galveston Island, TX 77550
+1(832) 380-4970


On Sun, May 13, 2018, 09:12 greatketch@... [amelyachtowners] <amelyachtowners@...> wrote:
 

Pat,


It is totally "normal" when picking a prop for a diesel engine to do exactly as Felxofold suggests.  You pick a propeller that allows the engine to turn its full rated RPM at full throttle. (which is where the engine power rating is specified). The way a propeller power curve is shaped, there is no advantage to operating the engine at its "maxiumum torque."

Most engine makers will insist on speed matching as part of the proper installation.  In fact, Volvo does on their other engines.  If you installed most marine diesel engines propped to run at 1500RPM below rating at full throttle, they would struggle, have significant maintenance issues, and have a shorter than expected lifespan.

With THIS engine in particular, Volvo did not insist. They even suggested in the engine manual that there are advantages to "over-propping" the engine and having it peak at lowe r RPM than its full rating. In fact you have to look really hard to even find Volvo mentioning the 4500 RPM number! I am not completely sure WHY Volvo felt this appropriate for this engine, but Amel took advantage of this flexibility in full throttle RPM, and propped it to full-throttle at about 3000RPM.  

I think the history of this engine in Amels supports that decision.  We do suffer from some issues (minor carbon build up in the turbo, and constant black soot on the hull) that come from it, but but they seem to have a long and relatively trouble free service life, as a rule.  Mine just turned 8000 hours.  If I figure 12,000 hours as a reasonable lifespan, that gives me another... 15 years :)

This is one of those places where someone coming from a long history with other boats looks at the Volvo installation in an Amel and decides right away that it is wrong...  but it works exactly like it is supposed to.

My wild speculation with what happened on this engine, is that that Perkins specified the max RPM with an eye to the Automotive market.  It was a popular engine in Land Rovers, among others. A redline RPM means something very different in an automobile, where running at maximum rated RPM is an unusual and short term event.  (At least the way I drive.) In addition, automobile engines that last 5000 hours are the exception, not the rule.

In a marine installation, an engine operates very high up on its power curve--all the time.  Volvo probably felt that operating the engine at 4500RPM continuously wasn&# 39;t a good idea for service and longevity, but for some reason didn't want to change the injection pump to lower the peak RPM and HP rating of the engine.  I suspect because they wanted to keep the 74HP rating as a sales tool--even if it was unrealistic for a typical marine installation.

Long and short of this is: Have flexofold specify a prop that will load your engine enough that it tops out at something between 2900 and 3300RPM.  You'll motor at 8 knots (full throttle), and be happy.

Bill Kinney
SM160, Harmonie
Rock Sound Harbour, Eleuthera, Bahamas

---In amelyachtowners@..., wrote :

I had flexofold suggest a prop and pitch that would allow the engine reach its max rpm , in my case 4500 . I now just read on the Max prop website , that their prop would also allow the engine to reach full rpm ,"in flat water." I wrote back to Flexofold that this did not sound correct , as my fixed prop does not allow me to get beyond 3000, and I have not read about anyone else able to reach rpms that high. I would think  reaching max torque would be the goal . Should a prop/ pitch allow an engine to obtain max rpms ? I don't know what to think or what is correct on this subject, and I may owe Flexofold a retraction.

Thanks,

Pat

SM #123

Patrick McAneny
 

Bill, Thanks for the follow up. I have been leaning more to the Max prop classic,they suggested the Easy , but its like a grand more and once the pitch is set than I don't see that its worth it. Since you have the Max prop, and I assume you also have the TMD22 78 hp , can you tell me what the size and pitch you have as well as your max rpm /speed ? Does it seem to have adequate power to punch through wind and waves and what rpm do you cruise at and at what speed? Sorry for all the questions , but I don't know of another SM with the Max prop .
Thanks Again,
Pat SM#123


-----Original Message-----
From: greatketch@... [amelyachtowners]
To: amelyachtowners
Sent: Sun, May 13, 2018 12:17 pm
Subject: Re: [Amel Yacht Owners] Re: Props and rpm

 


Yes, Amel overpitched the prop on the Volvo on purpose. Volvo suggested that one of several reasons that you might want to restrict the top speed of the engine was "reduced noise."  

 I don't know what Amel did on the Yanmars.  I am sure somebody here can answer that...

I wouldn't tell them "under 3000" but rather give them 3000 as the target.  Lower speeds will result in lower net power output from the engine, so you don't want to drop much.

I have owned two boats with a "Classic" 3 blade MaxProp (including Harmonie) and have been very happy with them.  They work, they are easy to care for, no bearings, seals, or other parts that we ar out.  Every haulout I take mine apart and clean and grease it.  I keep a zinc on the end, and all has been good.

I have no experience with Flexofold specifically.  My fleet experience with folding props is limited to Martec brand props on racing sailboats.  Not applicable to a SM installation, but I didn't particularly like them, both from a maintenance and a performance under power standpoint. The maintenance issue was wear of the pivot pins. They needed regular replacement.

In the real world, I very much doubt there is anything other than a theoretical performance difference between any of the major brands of folding or feathering props.  Certainly in sailing performance, and even in motoring the differences aren't really going to be significant. Many folding props struggle a bit with reverse, but I suspect that is more a case of the helmsman needing to rev the engine more than he was used to.

One nice thing about a Maxprop: Based the experiences of other SM owners who have them installed by Amel in the early production run, you know exactly which one to get and where to set the adjustable pitch without trial and error. No need to pay the premium for the model with in-water pitch adjustment.

And as a total aside.... Speaking of "premium," the new 5 blade Maxprop is a beautiful piece of machinework!  Priced like fine jewelry, but I imagine it is runs really, really smoothly.  Certainly not worth it for the two or three hundred hours a year I have the engine running, but it would certainly make me the star of the boatyard at haulout!

Bill Kinney
Sm#160, Harmonie
Rock Sound Harbour, Eleuthera, Bahamas

---In amelyachtowners@..., wrote :

Bill, Thank you for your detailed reply. If I understand you correctly and correct me if I am wrong, Amel purposely over pitched my fixed prop to restrain it from attaining higher rpms and Volvo is fine with that. So, can owners with Yanmars obtain max rpms? I can't imagine I would want to hear my engine running higher than 3000 rpm , I feel as though I am over stressing it at that , I know it stresses me . So whatever prop I should buy , I should have them sell me a prop size and pitc h that keeps my TMD22a under 3000 rpm. I know you were involved in the charter business , do you have any experience with Flexofold or Max Prop ?
Thanks Again,
Pat
SM #123

greatketch@...
 

Pat,

I'll have to look deeper for the size, I know it is written down on the boat SOMEWHERE!  I do know the pitch setting is 20 degrees, left rotating.

My understanding is all of the early production runs of Super Maramus had MaxProps from the factory.  Autoprops do not fit the earlier SMs because there is not enough clearance for the blades to swing round.  I am sure Bill Rouse or Joel Potter can at least approximate the hull number when the keel was modified to allow the Autoprop room to swing.  I'll bet it is buried in the old posts here somewhere...

Bill Kinney
SM160, Harmonie
Rock Sound Harbour, Eleuthera, Bahamas

Patrick McAneny
 

Bill, I was going to buy a Autoprop from Alexandre , when Olivier informed me that the boats were modified to fit the Autoprop. I would be interested in the performance , eg. cruising speed /rpm ,max speed/rpm and appreciate your overall assessment of the Max prop on a SM.,particularly as you have the same engine I do.
Thanks
Pat SM#123


-----Original Message-----
From: greatketch@... [amelyachtowners]
To: amelyachtowners
Sent: Mon, May 14, 2018 12:26 am
Subject: Re: [Amel Yacht Owners] Re: Props and rpm

 
Pat,

I'll have to look deeper for the size, I know it is written down on the boat SOMEWHERE!  I do know the pitch setting is 20 degrees, left rotating.

My understanding is all of the early production runs of Super Maramus had MaxProps from the factory.  Autoprops do not fit the earlier SMs because there is not enough clearance for the blades to swing round.  I am sure Bill Rouse or Joel Potter can at least approximate the hull number when the keel was modified to allow the Autoprop room to swing.  I'll bet it is buried in the old posts here somewhere...

Bill Kinney
SM160, Harmonie
Rock Sound Harbour, Eleuthera, Bahamas

greatketch@...
 

Pat, 

At full throttle, and a clean bottom, I motor at 8.1 knots at 3100 RPM.

My normal "around the harbor" cruising speed is 6 knots at 2000-2100 RPM

Once you go away from a fixed prop, it is my overall opinion is that the relative differences between the various prop options is so small in normal operation you'll never notice, so if I had to pick a new prop, I would pick the cheapest one that I felt was robust and well designed, and minimized maintenance.  If my passion was racing, I might be paying a premium for low drag, if I was on a motorsailor and put 1000 hours a year on my engine I might pay extra for improved motoring performance, but neither of those are on my valued added radar.

Only once have I ever feel like the boat could have used more power.  Coming out of the southern end of the Cape Cod Canal, with a following tide, into the teeth of the afternoon southeasterlies. (All the New England sailors on the forum are smiling knowingly about now...) 

The 25 knot winds driving straight into the south tidal current had kicked up miles of the shortest, steepest chop I have ever had the misfortune to have to motor into.  And motor was the only choice, the narrow channel was straight into the wind.  We made progress, but it was slow and very uncomfortable. As a small consolation, we were making slightly better time than the other boats around us. 

Once we got to deeper water where we could bear off and sail without the engine our VMG went way up, and we were a lot more comfortable--and we left those other boats, still motoring,  further behind on each tack.

Bill Kinney
SM160, Harmonie,
Rock Sound Harbour, Eleuthera, Bahamas

---In amelyachtowners@..., <sailw32@...> wrote :

Bill, I was going to buy a Autoprop from Alexandre , when Olivier informed me that the boats were modified to fit the Autoprop. I would be interested in the performance , eg. cruising speed /rpm ,max speed/rpm and appreciate your overall assessment of the Max prop on a SM.,particularly as you have the same engine I do.
Thanks
Pat SM#123


Patrick McAneny
 

Bill, I spoke to Max Prop and he seemed pretty familiar with Amels and I am awaiting a quote. Thanks for the info.
Pat SM#123


-----Original Message-----
From: greatketch@... [amelyachtowners]
To: amelyachtowners
Sent: Mon, May 14, 2018 11:48 am
Subject: Re: [Amel Yacht Owners] Re: Props and rpm

 
Pat, 

At full throttle, and a clean bottom, I motor at 8.1 knots at 3100 RPM.

My normal "around the harbor" cruising speed is 6 knots at 2000-2100 RPM

Once you go away from a fixed prop, it is my overall opinion is that the relative differences between the various prop options is so small in normal operation you'll never notice, so if I had to pick a new prop, I would pick the cheapest one that I felt was robust and well designed, and minimized maintenance.  If my passion was racing, I might be paying a premium for low drag, if I was on a motorsailor and put 1000 hours a year on my engine I might pay extra for improved motoring performance, but neither of those are on my valued added radar.

Only once have I ever feel like the boat could have used more power.  Coming out of the southern end of the Cape Cod Canal, with a following tide, into the te eth of the afternoon southeasterlies. (All the New England sailors on the forum are smiling knowingly about now...) 

The 25 knot winds driving straight into the south tidal current had kicked up miles of the shortest, steepest chop I have ever had the misfortune to have to motor into.  And motor was the only choice, the narrow channel was straight into the wind.  We made progress, but it was slow and very uncomfortable. As a small consolation, we were making slightly better time than the other boats around us. 

Once we got to deeper water where we could bear off and sail without the engine our VMG went way up, and we were a lot more comfortable--and we left those other boats, still motoring,  further behind on each tack.

Bill Kinney
SM160, Harmonie,
Rock Sound Harbour, Eleuthera, Bahamas

---In amelyachtowners@...,
Bill, I was going to buy a Autoprop from Alexandre , when Olivier informed me that the boats were modified to fit the Autoprop. I would be interested in the performance , eg. cruising speed /rpm ,max speed/rpm and appreciate your overall assessment of the Max prop on a SM.,particularly as you have the same engine I do.
Thanks
Pat SM#123


Ian Townsend
 

That's great Pat. If you don't mind, can you please share what they tell you? Size, pitch and pricing. We are also considering a MaxProp to replace our three bladed fixed. Thx a bunch.

Ian
S/V Loca Lola II 
SM153

On May 14, 2018, at 1:30 PM, Patrick Mcaneny sailw32@... [amelyachtowners] <amelyachtowners@...> wrote:

 

Bill, I spoke to Max Prop and he seemed pretty familiar with Amels and I am awaiting a quote. Thanks for the info.

Pat SM#123


-----Original Message-----
From: greatketch@... [amelyachtowners] <amelyachtowners@...>
To: amelyachtowners <amelyachtowners@...>
Sent: Mon, May 14, 2018 11:48 am
Subject: Re: [Amel Yacht Owners] Re: Props and rpm

 
Pat, 

At full throttle, and a clean bottom, I motor at 8.1 knots at 3100 RPM.

My normal "around the harbor" cruising speed is 6 knots at 2000-2100 RPM

Once you go away from a fixed prop, it is my overall opinion is that the relative differences between the various prop options is so small in normal operation you'll never notice, so if I had to pick a new prop, I would pick the cheapest one that I felt was robust and well designed, and minimized maintenance.  If my passion was racing, I might be paying a premium for low drag, if I was on a motorsailor and put 1000 hours a year on my engine I might pay extra for improved motoring performance, but neither of those are on my valued added radar.

Only once have I ever feel like the boat could have used more power.  Coming out of the southern end of the Cape Cod Canal, with a following tide, into the te eth of the afternoon southeasterlies. (All the New England sailors on the forum are smiling knowingly about now...) 

The 25 knot winds driving straight into the south tidal current had kicked up miles of the shortest, steepest chop I have ever had the misfortune to have to motor into.  And motor was the only choice, the narrow channel was straight into the wind.  We made progress, but it was slow and very uncomfortable. As a small consolation, we were making slightly better time than the other boats around us. 

Once we got to deeper water where we could bear off and sail without the engine our VMG went way up, and we were a lot more comfortable--and we left those other boats, still motoring,  further behind on each tack.

Bill Kinney
SM160, Harmonie,
Rock Sound Harbour, Eleuthera, Bahamas

---In amelyachtowners@..., wrote :

Bill, I was going to buy a Autoprop from Alexandre , when Olivier informed me that the boats were modified to fit the Autoprop. I would be interested in the performance , eg. cruising speed /rpm ,max speed/rpm and appreciate your overall assessment of the Max prop on a SM.,particularly as you have the same engine I do.
Thanks
Pat SM#123


Patrick McAneny
 

Ian, They just sent me a quote for a 3 blade classic 22x16 for $3450. Per Joels suggestion I am going to speak with Maud and see what the pitch was when Amel  installed Max props on the SM years ago,I need to talk to her anyway.  PYI quote was higher $3,750., they suggested I call PYachts in Annapolis to see if I could get a discount and did. I am going to provide them with a wholesale number a friend gave me today and see if they can do better. Maybe buying two would get a better price.
Thanks,
Pat
SM#123


-----Original Message-----
From: Ian Townsend smlocalola@... [amelyachtowners]
To: amelyachtowners
Sent: Mon, May 14, 2018 1:33 pm
Subject: Re: [Amel Yacht Owners] Re: Props and rpm

 
That's great Pat. If you don't mind, can you please share what they tell you? Size, pitch and pricing. We are also considering a MaxProp to replace our three bladed fixed. Thx a bunch.

Ian
S/V Loca Lola II 
SM153

On May 14, 2018, at 1:30 PM, Patrick Mcaneny sailw32@... [amelyachtowners] <amelyachtowners@...> wrote:

 
Bill, I spoke to Max Prop and he seemed pretty familiar with Amels and I am awaiting a quote. Thanks for the info.
Pat SM#123


-----Original Message-----
From: greatketch@... [amelyachtowners] <amelyachtowners@...>
To: amelyachtowners <amelyachtowners@...>
Sent: Mon, May 14, 2018 11:48 am
Subject: Re: [Amel Yacht Owners] Re: Props and rpm

 
Pat, 

At full throttle, and a clean bottom, I motor at 8.1 knots at 3100 RPM.

My normal "around the harbor" cruising speed is 6 knots at 2000-2100 RPM

Once you go away from a fixed prop, it is my overall opinion is that the relative differences between the various prop options is so small in normal operation you'll never notice, so if I had to pick a new prop, I would pick the cheapest one that I felt was robust and well designed, and minimized maintenance.  If my passion was racing, I might be paying a premium for low drag, if I was on a motorsailor and put 1000 hours a year on my engine I might pay extra for improved motoring performance, but neither of those are on my valued added radar.

Only once have I ever feel like the boat could have used more power.  Coming out of the southern end of the Cape Cod Canal, with a following tide, into the te eth of the afternoon southeasterlies. (All the New England sailors on the forum are smiling knowingly about now...) 

The 25 knot winds driving straight into the south tidal current had kicked up miles of the shortest, steepest chop I have ever had the misfortune to have to motor into.  And motor was the only choice, the narrow channel was straight into the wind.  We made progress, but it was slow and very uncomfortable. As a small consolation, we were making slightly better time than the other boats around us. 

Once we got to deeper water where we could bear off and sail without the engine our VMG went way up, and we were a lot more comfortable--and we left those other boats, still motoring,  further behind on each tack.

Bill Kinney
SM160, Harmonie,
Rock Sound Harbour, Eleuthera, Bahamas

---In amelyachtowners@..., wrote :

Bill, I was going to buy a Autoprop from Alexandre , when Olivier informed me that the boats were modified to fit the Autoprop. I would be interested in the performance , eg. cruising speed /rpm ,max speed/rpm and appreciate your overall assessment of the Max prop on a SM.,particularly as you have the same engine I do.
Thanks
Pat SM#123


Ian Townsend
 

Roger that. Interested. Standing by.

Ian
S/V Loca Lola II 
SM153

On May 14, 2018, at 7:47 PM, Patrick Mcaneny sailw32@... [amelyachtowners] <amelyachtowners@...> wrote:

 

Ian, They just sent me a quote for a 3 blade classic 22x16 for $3450. Per Joels suggestion I am going to speak with Maud and see what the pitch was when Amel  installed Max props on the SM years ago,I need to talk to her anyway.  PYI quote was higher $3,750., they suggested I call PYachts in Annapolis to see if I could get a discount and did. I am going to provide them with a wholesale number a friend gave me today and see if they can do better. Maybe buying two would get a better price.

Thanks,
Pat
SM#123


-----Original Message-----
From: Ian Townsend smlocalola@... [amelyachtowners] <amelyachtowners@...>
To: amelyachtowners <amelyachtowners@...>
Sent: Mon, May 14, 2018 1:33 pm
Subject: Re: [Amel Yacht Owners] Re: Props and rpm

 
That's great Pat. If you don't mind, can you please share what they tell you? Size, pitch and pricing. We are also considering a MaxProp to replace our three bladed fixed. Thx a bunch.

Ian
S/V Loca Lola II 
SM153

On May 14, 2018, at 1:30 PM, Patrick Mcaneny sailw32@... [amelyachtowners] <amelyachtowners@...> wrote:

 
Bill, I spoke to Max Prop and he seemed pretty familiar with Amels and I am awaiting a quote. Thanks for the info.
Pat SM#123


-----Original Message-----
From: greatketch@... [amelyachtowners] <amelyachtowners@...>
To: amelyachtowners <amelyachtowners@...>
Sent: Mon, May 14, 2018 11:48 am
Subject: Re: [Amel Yacht Owners] Re: Props and rpm

 
Pat, 

At full throttle, and a clean bottom, I motor at 8.1 knots at 3100 RPM.

My normal "around the harbor" cruising speed is 6 knots at 2000-2100 RPM

Once you go away from a fixed prop, it is my overall opinion is that the relative differences between the various prop options is so small in normal operation you'll never notice, so if I had to pick a new prop, I would pick the cheapest one that I felt was robust and well designed, and minimized maintenance.  If my passion was racing, I might be paying a premium for low drag, if I was on a motorsailor and put 1000 hours a year on my engine I might pay extra for improved motoring performance, but neither of those are on my valued added radar.

Only once have I ever feel like the boat could have used more power.  Coming out of the southern end of the Cape Cod Canal, with a following tide, into the te eth of the afternoon southeasterlies. (All the New England sailors on the forum are smiling knowingly about now...) 

The 25 knot winds driving straight into the south tidal current had kicked up miles of the shortest, steepest chop I have ever had the misfortune to have to motor into.  And motor was the only choice, the narrow channel was straight into the wind.  We made progress, but it was slow and very uncomfortable. As a small consolation, we were making slightly better time than the other boats around us. 

Once we got to deeper water where we could bear off and sail without the engine our VMG went way up, and we were a lot more comfortable--and we left those other boats, still motoring,  further behind on each tack.

Bill Kinney
SM160, Harmonie,
Rock Sound Harbour, Eleuthera, Bahamas

---In amelyachtowners@..., wrote :

Bill, I was going to buy a Autoprop from Alexandre , when Olivier informed me that the boats were modified to fit the Autoprop. I would be interested in the performance , eg. cruising speed /rpm ,max speed/rpm and appreciate your overall assessment of the Max prop on a SM.,particularly as you have the same engine I do.
Thanks
Pat SM#123


greatketch@...
 

Pat,

For the classic model MaxProp, the pitch is adjustable over a wide range, so for purchase the numbers that are critical are the prop diameter and the bore for the shaft.  If you need confirmation, I am in the Bahamas, so can go overboard with a tape measure and confirm the prop diameter...   My recollection for the shaft dimension is 35mm... but confirm that before you sign anything!

The primary thing about the Classic that is different on the newer models is changing the pitch requires complete disassembly of the hub. PYI officially says this must be done out of the water, but they do have a list of divers who can tackle the job that they will share if asked.  The only one I personally know works in San Francisco Bay...

Bill Kinney
SM160, Harmonie
Little San Salvador, Bahamas
http://fetchinketch.net

Patrick McAneny
 

Bill, The quote described it as 22x16 70 mm hub , I took a couple of measurements of the diameter with a caliper , two as it is tapered . I will confirm with Maud before placing an order.
Thanks,
Pat
SM#123


-----Original Message-----
From: greatketch@... [amelyachtowners]
To: amelyachtowners
Sent: Mon, May 14, 2018 9:15 pm
Subject: Re: [Amel Yacht Owners] Re: Props and rpm

 
Pat,

For the classic model MaxProp, the pitch is adjustable over a wide range, so for purchase the numbers that are critical are the prop diameter and the bore for the shaft.  If you need confirmation, I am in the Bahamas, so can go overboard with a tape measure and confirm the prop diameter...   My recollection for the shaft dimension is 35mm... but confirm that before you sign anything!

The primary thing about the Classic that is different on the newer models is changing the pitch requires complete disassembly of the hub. PYI officially says this must be done out of the water, but they do have a list of divers who can tackle the job that they will share if asked.  The only one I personally know works in San Francisco Bay...

Bill Kinney
SM160, Harmonie
Little San Salvador, Bahamas