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Author Topic:   NANTUCKET 190 with 115-HP: Propeller Choice

Yiddil posted 10-15-2004 12:46 AM ET (US)
I have a standard Aluminum BLack Max 13 X 19 [i.e., 19-inch pitch three-blade] on my 190 NANTUCKET with 115-HP two-stroke. She runs fine and WOT is [around] 5200 RPM. I thought I'd switch to a stainless steel Mercury prop to get [more engine speed]. I have heard she will run better with the Stainless steel prop. I got a Vengence 13 X 18 prop, thinking from what I heard from others that going down to 18-inch pitch was okay for a SS propeller. Is that correct?
I have also heard that I should go to a 16-inch pitch. Now I am confused. Haven't put [the 18-inch pitch propeller] on yet.
What will be the estimated difference between the Vengeance 18-pitch or 16-pitch [as compared to] the Aluminum Black Max 19-pitch. I guess I am concerned I got the wrong SS propeller. I know [literally] nothing about props and the math for them. Thanks in advance for your reply and help, Henry
LHG posted 10-15-2004 02:50 PM ET (US)
You do NOT want that particular engine over its redline of 5250!
Depending on engine mounting height, in the second hole you could try an 18-inch SS Vengeance prop, but watch redline. An alternative would be a 19-inch Michigan Wheel Rapture which will bring the RPM down 100-200. Not sure she will turn a 20-inch Merc Laser II, even if you go up to the 3rd hole, but if so, this would be my first choice. The first two SS propellers will definitely give you a little better holding and top speed than the aluminum 19.
Yiddil posted 10-16-2004 12:58 AM ET (US)
THanks, I called WHaler dealer and they suggest a SS 13 X 16 pitch. I am to confused. I think the Nantucket' s Mercury 115-HO two-stroke engine is standard in the 2nd hole. I guess I will try [raising the engine one hole] and see what happens. WHaler says 16 pitch, [because the engine does not] have the power for the 18 pitch.
Why they would say that? What is really right? Any ideas why [that Boston Whaler would recommend a propeller that I think is wrong]?
Whalerider posted 10-16-2004 08:50 AM ET (US)
Call Powertech Props (www.ptprop.com) and tell them what you have and your goals. They will help you select the right prop. If its not what you need they will exchange or adjust as many times as required until you are happy
I have had at least 7 props from them on different boats and was VERY pleased. I am running a Powertech vented 4 blade offshore prop on my Nantucket. Really helped with bow rise and my midrange improved. I am pleased after they did some minor tweeking.
Highly recommend them, what do you have to loose.
Mark
p.s. It has been my experience that boat makers dont usually select the correct prop. Seems like they would! According to BW the Mercury Mirage prop is perfect for the Nantucket/150 opti and it was a DOG!
kamie posted 10-16-2004 11:11 AM ET (US)
Since you have the 18 Vengance I would give it a try. If you don't like it you can always sell it.
If you want to try my 19 Laser II you are welcome to try it. Next time I am out I need to test the Vensura 17p anyway to see how she runs.
LHG posted 10-16-2004 03:05 PM ET (US)
The Merc 115 and 150's don't use the same gearcase/prop series.
It does seem strange that a 19-inch aluminum would translate to a 16-inch Vengeance SS.
Yiddil posted 10-17-2004 01:19 AM ET (US)
You are telling me a 16 sounds strange. I will meet up with Kamie and try [some propeller] when it finally arrives and see. Whaler definitely says 16, I asked again at the Annapolis Boat Show today. LHG, Kamie, all, thanks. I still don't understand what the difference will be between the 19 and the 16. I am just looking for a bit more bite, holding and top speed. Henry
Whalerider posted 10-17-2004 09:46 PM ET (US)
Well...even if the 16" pitch has a lot of cup you are going to loose quite a bit off the top end vs. the Aluminum 19".
Like I hinted earlier...talk a prop maker, they are the experts, they do this stuff all day every day.
jimh posted 10-18-2004 12:52 AM ET (US)
Henry, If you want to learn about the mathematics of propellers, I invite you to read the article in the Reference section that explains how to compute speed and slip. There is a series of several articles that will help you understand more about propellers See:
http://continuouswave.com/whaler/reference/prop.html
If Boston Whaler recommended a particular propeller with your boat and motor combination, it is probably based on their experience with testing the boat. I don't think they just pull these numbers out of a hat. They have probably tested various combinations.
At least six combinations of motor and propeller on a NANTUCKET 190 are reported and analyzed in a Reference article. See:
http://continuouswave.com/whaler/reference/190Nantucket.html
You mention that you anticipate increasing your engine speed by changing to a stainless steel propeller. This is probably not going to happen. And, as LHG has warned, you do not want to run the 115-HP Mercury two-stroke above its rated top speed of 5250 RPM. You really don't want to run any engine above its rated speed, but this particular engine has a fairly low top speed, and you must observe that limit.
You mention that you are looking for better "bite." This is probably going to happen with a stainless steel performance propeller. It is also the reason the pitch recommended was lower. If the propeller has better "bite" it will be harder for the engine to turn (less slipping), and thus the pitch may have to be lower.
When making comparisons between propellers, it is important to maintain as many variables as constant as possible. Keep the boat weight and water conditions as similar as possible, and keep accurate records of speeds noted.
jimh posted 10-18-2004 12:52 AM ET (US)
[A duplicate of this original article posted to another forum has been deleted.]
Yiddil posted 10-19-2004 08:29 PM ET (US)
Jim, downloaded the material, not sure Ill make heads nor tails out of it, but Ill try....thanks everyone....now if it would only stop raining:))

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Author	Topic: NANTUCKET 190 with 115-HP: Propeller Choice
Yiddil	posted 10-15-2004 12:46 AM ET (US) I have a standard Aluminum BLack Max 13 X 19 [i.e., 19-inch pitch three-blade] on my 190 NANTUCKET with 115-HP two-stroke. She runs fine and WOT is [around] 5200 RPM. I thought I'd switch to a stainless steel Mercury prop to get [more engine speed]. I have heard she will run better with the Stainless steel prop. I got a Vengence 13 X 18 prop, thinking from what I heard from others that going down to 18-inch pitch was okay for a SS propeller. Is that correct? I have also heard that I should go to a 16-inch pitch. Now I am confused. Haven't put [the 18-inch pitch propeller] on yet. What will be the estimated difference between the Vengeance 18-pitch or 16-pitch [as compared to] the Aluminum Black Max 19-pitch. I guess I am concerned I got the wrong SS propeller. I know [literally] nothing about props and the math for them. Thanks in advance for your reply and help, Henry
LHG	posted 10-15-2004 02:50 PM ET (US) You do NOT want that particular engine over its redline of 5250! Depending on engine mounting height, in the second hole you could try an 18-inch SS Vengeance prop, but watch redline. An alternative would be a 19-inch Michigan Wheel Rapture which will bring the RPM down 100-200. Not sure she will turn a 20-inch Merc Laser II, even if you go up to the 3rd hole, but if so, this would be my first choice. The first two SS propellers will definitely give you a little better holding and top speed than the aluminum 19.
Yiddil	posted 10-16-2004 12:58 AM ET (US) THanks, I called WHaler dealer and they suggest a SS 13 X 16 pitch. I am to confused. I think the Nantucket' s Mercury 115-HO two-stroke engine is standard in the 2nd hole. I guess I will try [raising the engine one hole] and see what happens. WHaler says 16 pitch, [because the engine does not] have the power for the 18 pitch. Why they would say that? What is really right? Any ideas why [that Boston Whaler would recommend a propeller that I think is wrong]?
Whalerider	posted 10-16-2004 08:50 AM ET (US) Call Powertech Props (www.ptprop.com) and tell them what you have and your goals. They will help you select the right prop. If its not what you need they will exchange or adjust as many times as required until you are happy I have had at least 7 props from them on different boats and was VERY pleased. I am running a Powertech vented 4 blade offshore prop on my Nantucket. Really helped with bow rise and my midrange improved. I am pleased after they did some minor tweeking. Highly recommend them, what do you have to loose. Mark p.s. It has been my experience that boat makers dont usually select the correct prop. Seems like they would! According to BW the Mercury Mirage prop is perfect for the Nantucket/150 opti and it was a DOG!
kamie	posted 10-16-2004 11:11 AM ET (US) Since you have the 18 Vengance I would give it a try. If you don't like it you can always sell it. If you want to try my 19 Laser II you are welcome to try it. Next time I am out I need to test the Vensura 17p anyway to see how she runs.
LHG	posted 10-16-2004 03:05 PM ET (US) The Merc 115 and 150's don't use the same gearcase/prop series. It does seem strange that a 19-inch aluminum would translate to a 16-inch Vengeance SS.
Yiddil	posted 10-17-2004 01:19 AM ET (US) You are telling me a 16 sounds strange. I will meet up with Kamie and try [some propeller] when it finally arrives and see. Whaler definitely says 16, I asked again at the Annapolis Boat Show today. LHG, Kamie, all, thanks. I still don't understand what the difference will be between the 19 and the 16. I am just looking for a bit more bite, holding and top speed. Henry
Whalerider	posted 10-17-2004 09:46 PM ET (US) Well...even if the 16" pitch has a lot of cup you are going to loose quite a bit off the top end vs. the Aluminum 19". Like I hinted earlier...talk a prop maker, they are the experts, they do this stuff all day every day.
jimh	posted 10-18-2004 12:52 AM ET (US) Henry, If you want to learn about the mathematics of propellers, I invite you to read the article in the Reference section that explains how to compute speed and slip. There is a series of several articles that will help you understand more about propellers See: http://continuouswave.com/whaler/reference/prop.html If Boston Whaler recommended a particular propeller with your boat and motor combination, it is probably based on their experience with testing the boat. I don't think they just pull these numbers out of a hat. They have probably tested various combinations. At least six combinations of motor and propeller on a NANTUCKET 190 are reported and analyzed in a Reference article. See: http://continuouswave.com/whaler/reference/190Nantucket.html You mention that you anticipate increasing your engine speed by changing to a stainless steel propeller. This is probably not going to happen. And, as LHG has warned, you do not want to run the 115-HP Mercury two-stroke above its rated top speed of 5250 RPM. You really don't want to run any engine above its rated speed, but this particular engine has a fairly low top speed, and you must observe that limit. You mention that you are looking for better "bite." This is probably going to happen with a stainless steel performance propeller. It is also the reason the pitch recommended was lower. If the propeller has better "bite" it will be harder for the engine to turn (less slipping), and thus the pitch may have to be lower. When making comparisons between propellers, it is important to maintain as many variables as constant as possible. Keep the boat weight and water conditions as similar as possible, and keep accurate records of speeds noted.
jimh	posted 10-18-2004 12:52 AM ET (US) [A duplicate of this original article posted to another forum has been deleted.]
Yiddil	posted 10-19-2004 08:29 PM ET (US) Jim, downloaded the material, not sure Ill make heads nor tails out of it, but Ill try....thanks everyone....now if it would only stop raining:))