A Prop Question

MantasR

Recruit
Joined
Mar 12, 2012
Messages
5
Hello Guys:

I saw one guy to submit this post


" I have a 196 with the 5.0 GXI/SX and like it a bunch. It started with a 21 pitch prop which was really fine at the elevation of Lake Powell (approx 3400...now at like 3200') It got great fuel economy and pulled freinds well. Top end was right around 50 with half fuel and 3 or 4 adults.
The end of last season I went to a 4 blade 20 pitch stainless. WOW! You better hold on to something. The bottom end is a big difference. We cruised with 8 (yes 8) large adults around Powell doing about 30 and still got decent economy. Of course wanting to see the real
performance, I unloaded everybody and everything of significant weight and went out by myself. When I got back, everyone kept asking me why I had that stupid grin on my face...Top end didn't (and really shouldn't have) improved much. I measured 53 by GPS. From a stand still the boat really lept onto plane. Pulling a friend that weighs about 225 on a slalom ski was ok before the new prop...now I just tell him to hold on as tight as he can and he really just pops out of the water."


I have 2003 Monterrey 206 with 5.0 GXI/SX, 90 hours on the motor. Seems to be that guy above was happy with 4 blade stainless steel 20 pinch prop. Do you think by going 21 or 22 pinch would still have a good plate time and better performance on the top end? That 5.0 GXI motor with 270 HP , a monster motor for 20-21 feet boat, plus it has a lot of tough. I do not think you will over-prop by going 21-22 pinch.

THANK YOU IN ADVANCE FOR ANY FEEDBACK THAT I CAN GET!!!
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,581
Hello Guys:

I saw one guy to submit this post


" I have a 196 with the 5.0 GXI/SX and like it a bunch. It started with a 21 pitch prop which was really fine at the elevation of Lake Powell (approx 3400...now at like 3200') It got great fuel economy and pulled freinds well. Top end was right around 50 with half fuel and 3 or 4 adults.
The end of last season I went to a 4 blade 20 pitch stainless. WOW! You better hold on to something. The bottom end is a big difference. We cruised with 8 (yes 8) large adults around Powell doing about 30 and still got decent economy. Of course wanting to see the real
performance, I unloaded everybody and everything of significant weight and went out by myself. When I got back, everyone kept asking me why I had that stupid grin on my face...Top end didn't (and really shouldn't have) improved much. I measured 53 by GPS. From a stand still the boat really lept onto plane. Pulling a friend that weighs about 225 on a slalom ski was ok before the new prop...now I just tell him to hold on as tight as he can and he really just pops out of the water."


I have 2003 Monterrey 206 with 5.0 GXI/SX, 90 hours on the motor. Seems to be that guy above was happy with 4 blade stainless steel 20 pinch prop. Do you think by going 21 or 22 pinch would still have a good plate time and better performance on the top end? That 5.0 GXI motor with 270 HP , a monster motor for 20-21 feet boat, plus it has a lot of tough. I do not think you will over-prop by going 21-22 pinch.

THANK YOU IN ADVANCE FOR ANY FEEDBACK THAT I CAN GET!!!

:welcome: to iboats

The previous guy had a 19 footer and you have a 20 footer, he said it did great and hope it did, but prop changes are complex. Someone says they can have 1600 p0unds (8 adults) in a boat and it preforms great and gets decent fuel economy, well lets just say I'm a skeptic.

Adding blades increases stern lift but lifting the stern can also cause other issues to happen, such as porpoising, touchy steering at WOT and can also reduce top speed.

Before you change a prop we would need to know what is your WOT RPM. ?
What do you want that your not getting now?
How do mainly use the boat now (tubing, skiing, just running around and floating)?
 

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,585
Years ago Mercury had an extremely great book all about props. I bought it and read it cover to cover a couple times. I actually still have that book. If you ever wanted to know anything about props and prop technology, you have to get and read that book. There is so much more involved in building a prop then I ever thought. Props are not just some paddles spinning around, there is much more precision progressive designs involved....a must read!
 

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Its hard to sit here and read a post like that and lend it credabiltiy unless he was under under propped from the start. It is quite possible that the poster was edging or hitting his rev limiter and was not aware of it happening...it is very brief and unless you did a sustained run for a mile or so a untrained ear might not even notice it. You should be aware that marine engine's have very mild cams and are not responsive to throttle input above 4500 rpm in essence i believe he was just floating at wot if he is truly is posting actual event's. We all read to pitch up to the desired wot rpm when actually one should pull down the engine to the desired rpm. If you want to get a accurate picture of your boats true performance and tune it right so to speak below is a very good guide and if that's too much work then as a wag a 21p 4 blade with no load ( read no people) should work for your boat and with 8 people it could well be a 18..in the middle is 19/20.


ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight

The below link would be a much more thorough list of data to provide if you're looking for detailed performance numbers,
http://forums.iboats.com/prop-questi...ml#post2336620
 
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Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,464
Hello Guys:

I saw one guy to submit this post


" I have a 196 with the 5.0 GXI/SX and like it a bunch. It started with a 21 pitch prop which was really fine at the elevation of Lake Powell (approx 3400...now at like 3200') It got great fuel economy and pulled freinds well. Top end was right around 50 with half fuel and 3 or 4 adults.
The end of last season I went to a 4 blade 20 pitch stainless. WOW! You better hold on to something. The bottom end is a big difference. We cruised with 8 (yes 8) large adults around Powell doing about 30 and still got decent economy. Of course wanting to see the real
performance, I unloaded everybody and everything of significant weight and went out by myself. When I got back, everyone kept asking me why I had that stupid grin on my face...Top end didn't (and really shouldn't have) improved much. I measured 53 by GPS. From a stand still the boat really lept onto plane. Pulling a friend that weighs about 225 on a slalom ski was ok before the new prop...now I just tell him to hold on as tight as he can and he really just pops out of the water."


I have 2003 Monterrey 206 with 5.0 GXI/SX, 90 hours on the motor. Seems to be that guy above was happy with 4 blade stainless steel 20 pinch prop. Do you think by going 21 or 22 pinch would still have a good plate time and better performance on the top end? That 5.0 GXI motor with 270 HP , a monster motor for 20-21 feet boat, plus it has a lot of tough. I do not think you will over-prop by going 21-22 pinch.

THANK YOU IN ADVANCE FOR ANY FEEDBACK THAT I CAN GET!!!

Ayuh,.... Welcome Aboard,....
I doubt the underlined statement, atleast til ya say what the current prop is, 'n what the rpms at Wot are,......

A 5.0l in a 20' hull, ain't much motor,...
 

MantasR

Recruit
Joined
Mar 12, 2012
Messages
5
With Existing porp 14.25 x 19:
43 mph at 4500 RPM
44 mph at 4750 RPM

I think max RPM on this motor is 5000, I didn't want to push past 4750 RPM

So with 14.25 x 20 I should run around 43 mph at 4300 RPM?
And with 14.25 x 21 I should run around 43 mph at 4100 RPM??

Do I understand this correctly? I'm looking for the best stainless steel prop for a mid range.. wanted to cruise half loaded at 35+MPH with 3100-3200 rpm
 

MantasR

Recruit
Joined
Mar 12, 2012
Messages
5
Its hard to sit here and read a post like that and lend it credabiltiy unless he was under under propped from the start. It is quite possible that the poster was edging or hitting his rev limiter and was not aware of it happening...it is very brief and unless you did a sustained run for a mile or so a untrained ear might not even notice it. You should be aware that marine engine's have very mild cams and are not responsive to throttle input above 4500 rpm in essence i believe he was just floating at wot if he is truly is posting actual event's. We all read to pitch up to the desired wot rpm when actually one should pull down the engine to the desired rpm. If you want to get a accurate picture of your boats true performance and tune it right so to speak below is a very good guide and if that's too much work then as a wag a 21p 4 blade with no load ( read no people) should work for your boat and with 8 people it could well be a 18..in the middle is 19/20.


ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight

The below link would be a much more thorough list of data to provide if you're looking for detailed performance numbers,
http://forums.iboats.com/prop-questi...ml#post2336620


1) Performance issue you are trying to correct. - I would like to cruise at 35+MPH with 3100-3200 RPM, mostly wanted to improve a mid range
2) Current prop manufacturer, model, aluminum or stainless as a minimum. - Current prop is 4 blade aluminum 14.25 x 19 pinch. Volvo Penta https://www.generalpropeller.com/3587522
3) Current prop diameter and pitch (required). 14.25 x19 https://www.generalpropeller.com/3587522
4) Wide open throttle RPM and speed with an average load (very helpful). With Existing porp 14.25 x 19: 43 mph at 4500 RPM and 44 mph at 4750 RPM. motor maxed at 5000 rpm
5) Engine/drive make, model, year, and HP - 2003 5.0 GXI, SX Drive, 270 HP
6) Boat make model, year, length and weight - 2003 Monterey 208 Montuna, 20 feet and 8 inches, weight 3500

Looking to improve a mid range, I do not like to run boat more that 3500-3700 RPM
 

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
No matter what RPM you want to cruise at the correct prop will be one that allows the engine to rev freely to the top of the manufacturer specified RPM range with normal to light loads. If you prop "up" past that the engine lugs and you are exposed to internal damage due to detonation and overheating of vulnerable components, resulting in tuliped valves, possible burnt pistons, etc.
 
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Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
I was trying to interpret your RPM numbers at WOT and typical load and am still unclear as to what the top RPM you can get to at WOT. I am not sure of your engine's RPM range from the manufacturer so I will just give some examples.

If your mfg specified RPM range high end is 4800 then if your prop allows the engine to go higher than that then you need the next step up in pitch. If you are 3-400 rpm lower than that then you need to drop down a step in pitch.
 

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
1) Performance issue you are trying to correct. - I would like to cruise at 35+MPH with 3100-3200 RPM, mostly wanted to improve a mid range
2) Current prop manufacturer, model, aluminum or stainless as a minimum. - Current prop is 4 blade aluminum 14.25 x 19 pinch. Volvo Penta https://www.generalpropeller.com/3587522
3) Current prop diameter and pitch (required). 14.25 x19 https://www.generalpropeller.com/3587522
4) Wide open throttle RPM and speed with an average load (very helpful). With Existing porp 14.25 x 19: 43 mph at 4500 RPM and 44 mph at 4750 RPM. motor maxed at 5000 rpm
5) Engine/drive make, model, year, and HP - 2003 5.0 GXI, SX Drive, 270 HP
6) Boat make model, year, length and weight - 2003 Monterey 208 Montuna, 20 feet and 8 inches, weight 3500

Looking to improve a mid range, I do not like to run boat more that 3500-3700 RPM



One last peice if you could that is the gearing ratio on you outdrive..A average load how ,many people on board and was the speed taken with gps...Last but not least i assume your can run the engine to 5000 rpm with your prop .....or is 4750 the highest the rpm will go?

My question's come from your posted top speed of 43mph that combo would or could do 53 with two people and a load of gas etc with 6 people no it would not..Did you use gps to measure the speed?
 
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MantasR

Recruit
Joined
Mar 12, 2012
Messages
5
One last peice if you could that is the gearing ratio on you outdrive..A average load how ,many people on board and was the speed taken with gps...Last but not least i assume your can run the engine to 5000 rpm with your prop .....or is 4750 the highest the rpm will go?

My question's come from your posted top speed of 43mph that combo would or could do 53 with two people and a load of gas etc with 6 people no it would not..Did you use gps to measure the speed?

I have Volvo Penta SX-M outdrive with 1:60 ratios, found a small tag on the left side of the drive. Number above ratios noted 3868891. And number below rations noted 4202076600 (picture attached)




RPM: I reached 4750 RPM pretty easily and left like motor could go at and beyond 5000 RPM (recommended WOT per manufacture are 4600-5000). Motor was quick to respond to the throttle even at 4750 RPM...

SPEED: My 1st post was just a copy and paste quote of the guy with 196 5.0 GXI motor and his experience with the props..Not me and Not for my boat( sorry if I mislead anyone..) My experience with my boat and 14.25x19 prop ===>>> speed taken with GPS app on my phone( I tested in the car on the way to the lake....pretty accurate), half tank of gas and only me in the boat: 43 MPH with 4500 RPM and 44 MPH with 4750 RPM. I left like the motor was revving louder from 4300 RPM to 4750 RPM but I was not getting much speed.

[FONT=&quot]to what I can understand...I have 3 candidates for my new prop:

#1 - http://boatpropellers.iboats.com/Vo...-148-20_Propeller/541/9101/?cart_id=886919092
3 BLADE STAINLESS STEEL 14 3/4 - 20 pitch

#2 - http://boatpropellers.iboats.com/Vo...993205_Propeller/541/11237/?cart_id=886919092
4 BLADE STAILESS STEEL 14 1/8 - 20 pitch

#3 - http://boatpropellers.iboats.com/Vo...153-20_Propeller/541/22458/?cart_id=886919092
4 BLADE STAINLESS STEEL 15 1/4 - 20 pitch - I FEEL LIKE THIS LAST ONE CAN BE AN OVER KILL - TO LARGE!!!

Which prop would you get to benefit your mid range/cruise on the boat and play safe( to be easy on the motor/drive) !!!!??? Send me a link.... :)

THANK YOU FOR ALL!!!!!![/FONT]
 

MantasR

Recruit
Joined
Mar 12, 2012
Messages
5
No matter what RPM you want to cruise at the correct prop will be one that allows the engine to rev freely to the top of the manufacturer specified RPM range with normal to light loads. If you prop "up" past that the engine lugs and you are exposed to internal damage due to detonation and overheating of vulnerable components, resulting in tuliped valves, possible burnt pistons, etc.

VERY VERY GOOD INFORMATION SIR!!! THANK YOU!!!
 

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Well there are two ways to go about this and its up to you

1. Take the boat out again and run it to full rpm that would be 5000..if you do that while at 5000 listen very closely for a very brief engine miss you would hardly be able to hear it just a nano second of hestitation. If it does which i am sure it would do your under propped.
2. Here's a bit of a guess but it will get you where you want to be and will do everything your looking for..Stilletto BayPro 2 in a 20 pitch a very agressive midrange and top end performance prop. Or the solas http://boatpropellers.iboats.com/Vol...****=886919092

Your current prop is slipping badly and either prop will improve that, The baypro would be the prop of choice you have a pm
 
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