1971 OUTRAGE, E-TEC 150: Propeller Selection

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Author Topic:   1971 OUTRAGE, E-TEC 150: Propeller Selection

JayR posted 10-21-2006 07:12 PM ET (US)
Specifics...
150 E-TEC
1971 Ribbed Outrage
Top speed, 43.5 MPH at 5250 RPM's
Current prop is a stock OMC aluminum 14.8 x 17
I would like to get the full RPM rating of 5800.
Which prop should I buy? I have access to nothing for trial purposes.
Any suggestions?
Thanks
jgkmmoore posted 10-21-2006 08:44 PM ET (US)
13 or 13.25 X 17 SST or Stiletto.Should bring you to around 55/5600.Better holeshot too.Believe a 15" would be too short. Tom Clark can probably inform you best.
Perry posted 10-22-2006 02:50 AM ET (US)
Would you really want to put a 13" diameter prop on a 21 foot Whaler with a 150 HP V6? A 13" diameter prop seems a little small to me.
Tom W Clark posted 10-23-2006 10:27 AM ET (US)
No. The Stiletto Advantage IIs are 14-1/4" diameter not 13-1/4".
A 14-1/4 x 15" Stiletto Advantage II will perform like a BRP 17' Pitch prop and would probably be a very good math for the E-Tec 150.
LHG posted 10-23-2006 01:04 PM ET (US)
Then, based on his numbers above, Jay would need a 15" BRP alum or a 13" Stiletto?
ratherwhalering posted 10-23-2006 01:23 PM ET (US)
Preliminary report: 1982 Outrage-18, 2007 E-TEC 150, 4-inch CMC set-back brackets, full fuel tank, stern seat, 2-batteries, lots of gear, 220 driver. Stiletto 14.25 x 17 Advantage. 47.5 MPH at 5500 RPM WOT. The engine needs to be raised 1-2 inches and is still in the 10 hour oiling period, so we are waiting for +/- 20 hours and 1/4 fuel tank load to complete a comprehensive performance report. Still, I agree that the 14.25 x 15-inch Stiletto Advantage II would be a very good match for your rig.
LHG posted 10-23-2006 01:32 PM ET (US)
On second look, Jay's stats don't add up. Existing prop seems more like a 19" pitch, rather than 17". Or speed (too high?) and RPM (too low?) are wrong for the 1.86 gears.
jimh posted 10-23-2006 01:32 PM ET (US)
There is a rule of thumb for propeller pitch changes on how they affect engine speed:

quote:
An increase in pitch of two inches will decrease engine speed 450-RPM, and vice versa.
This can be applied with propellers in the same family. You cannot rely on propellers of different design and manufacturer to adhere to the rule because the actual pitch rating may not be consistent with the initial propeller.
In this instance, we have a boat with a a 17-inch propeller and its engine turns 5,250-RPM. According to the rule of thumb, if we decrease pitch to 15-inches (and stay in the same brand/family of propellers) the engine speed should increase to 5,700-RPM.
The effect of this on boat speed can be estimated with the propeller calculator. The result is an estimated speed of just below 42-MPH.
The SLIP value that the original data produced was quite low, below 5-percent. This is unusually low for a single engine installation. It is more typical to see a SLIP factor of about 10-percent on a single engine boat. (On the other hand the 1971 OUTRAGE is a rather light and easily driven boat, so it may permit propellers to become quite efficient when propeller it at higher speeds.)
When you get a SLIP value that is below 10-percent for a single engine installation (or below 5-percent for a twin engine installation) it is often associated with a propeller whose actual pitch is probably somewhat higher than the marked pitch value. In this case, the propeller reported as a 17-inch pitch may be slightly taller.
ratherwhalering posted 10-23-2006 04:58 PM ET (US)
Sorry, I screwed up my calculations. 46.8 MPH. I'll set the GPS to MPH for the comprehensive report.
JayR posted 10-24-2006 08:53 PM ET (US)
Sorry it took me so long to get back.
I've had several instances where I opened her up and I am certain the speed I gave is accurate. Two GPS readings... Both read the same. The tach is the I-Command series and the analog and digital are identical.
Prop not a 17? Hull more efficient than most due to weight?
I'm at a loss.....
John W posted 10-26-2006 08:39 PM ET (US)
Jay,
I run a 1999, 17" pitch stock OMC aluminum prop on a 71 Outrage. My prop has some dings on the lead edges. Motor is a 1999 carb Johnson v6 150hp. Top speed is 41.5-43 mph at 5300-5400 rpm. My motor redlines at 5500. I don't know if the gearing is the same as yours or not. I'm surprized you're not getting a couple extra mph out of yours, but I don't think the OMC aluminum props are very good in terms of top speed.
As you know, this flat bottom, light weight boat is easily driven in terms of planing speed to 35mph or so. But because the boat does not lift out of the water at high speeds the way many modern hull designs do, it seems to me that the boat doesn't want to go much over 40mph unless a lot of horsepower is applied. I think to get this hull to 50 mph you need 200hp or more. But given that the boat is not very comfortable on anything but flat calm water over 40mph anyway, I don't see the point in maxing out top speed on this hull. (I think a 115 would probably be enough hp for easy cruising at 25 to 30mph, which is the boat's sweet spot in my opinion).
If you could borrow a Stilleto 15 or 17 pitch, I think you would see a couple mph improvement on top end. But I know you have kept an aluminum prop due to rocks in your boating area.
I assume the motor is out of whatever "break in" period that is programmed into its chips? Is it possible that the rpm's might increase over time slightly once the motor is out of "break in" mode??
Peter posted 10-26-2006 09:04 PM ET (US)
The 60 degree carbureted OMC 150s have a reputation of being pretty strong motors so I don't think that the E-TEC 150 would be good for a few extra MPH over one of those. Seems to me that Jay's results are consistent.
JayR posted 10-27-2006 10:33 PM ET (US)
I've only 20 hours or so on it. That's only about 10% of the use I expected for the summer.....
I suspect it is still in the break-in period at this point.
Hopefully I'll have her out again this week.
Thanks, I'll give it some time before making any changes.

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Author	Topic: 1971 OUTRAGE, E-TEC 150: Propeller Selection
JayR	posted 10-21-2006 07:12 PM ET (US) Specifics... 150 E-TEC 1971 Ribbed Outrage Top speed, 43.5 MPH at 5250 RPM's Current prop is a stock OMC aluminum 14.8 x 17 I would like to get the full RPM rating of 5800. Which prop should I buy? I have access to nothing for trial purposes. Any suggestions? Thanks
jgkmmoore	posted 10-21-2006 08:44 PM ET (US) 13 or 13.25 X 17 SST or Stiletto.Should bring you to around 55/5600.Better holeshot too.Believe a 15" would be too short. Tom Clark can probably inform you best.
Perry	posted 10-22-2006 02:50 AM ET (US) Would you really want to put a 13" diameter prop on a 21 foot Whaler with a 150 HP V6? A 13" diameter prop seems a little small to me.
Tom W Clark	posted 10-23-2006 10:27 AM ET (US) No. The Stiletto Advantage IIs are 14-1/4" diameter not 13-1/4". A 14-1/4 x 15" Stiletto Advantage II will perform like a BRP 17' Pitch prop and would probably be a very good math for the E-Tec 150.
LHG	posted 10-23-2006 01:04 PM ET (US) Then, based on his numbers above, Jay would need a 15" BRP alum or a 13" Stiletto?
ratherwhalering	posted 10-23-2006 01:23 PM ET (US) Preliminary report: 1982 Outrage-18, 2007 E-TEC 150, 4-inch CMC set-back brackets, full fuel tank, stern seat, 2-batteries, lots of gear, 220 driver. Stiletto 14.25 x 17 Advantage. 47.5 MPH at 5500 RPM WOT. The engine needs to be raised 1-2 inches and is still in the 10 hour oiling period, so we are waiting for +/- 20 hours and 1/4 fuel tank load to complete a comprehensive performance report. Still, I agree that the 14.25 x 15-inch Stiletto Advantage II would be a very good match for your rig.
LHG	posted 10-23-2006 01:32 PM ET (US) On second look, Jay's stats don't add up. Existing prop seems more like a 19" pitch, rather than 17". Or speed (too high?) and RPM (too low?) are wrong for the 1.86 gears.
jimh	posted 10-23-2006 01:32 PM ET (US) There is a rule of thumb for propeller pitch changes on how they affect engine speed: quote: An increase in pitch of two inches will decrease engine speed 450-RPM, and vice versa. This can be applied with propellers in the same family. You cannot rely on propellers of different design and manufacturer to adhere to the rule because the actual pitch rating may not be consistent with the initial propeller. In this instance, we have a boat with a a 17-inch propeller and its engine turns 5,250-RPM. According to the rule of thumb, if we decrease pitch to 15-inches (and stay in the same brand/family of propellers) the engine speed should increase to 5,700-RPM. The effect of this on boat speed can be estimated with the propeller calculator. The result is an estimated speed of just below 42-MPH. The SLIP value that the original data produced was quite low, below 5-percent. This is unusually low for a single engine installation. It is more typical to see a SLIP factor of about 10-percent on a single engine boat. (On the other hand the 1971 OUTRAGE is a rather light and easily driven boat, so it may permit propellers to become quite efficient when propeller it at higher speeds.) When you get a SLIP value that is below 10-percent for a single engine installation (or below 5-percent for a twin engine installation) it is often associated with a propeller whose actual pitch is probably somewhat higher than the marked pitch value. In this case, the propeller reported as a 17-inch pitch may be slightly taller.
ratherwhalering	posted 10-23-2006 04:58 PM ET (US) Sorry, I screwed up my calculations. 46.8 MPH. I'll set the GPS to MPH for the comprehensive report.
JayR	posted 10-24-2006 08:53 PM ET (US) Sorry it took me so long to get back. I've had several instances where I opened her up and I am certain the speed I gave is accurate. Two GPS readings... Both read the same. The tach is the I-Command series and the analog and digital are identical. Prop not a 17? Hull more efficient than most due to weight? I'm at a loss.....
John W	posted 10-26-2006 08:39 PM ET (US) Jay, I run a 1999, 17" pitch stock OMC aluminum prop on a 71 Outrage. My prop has some dings on the lead edges. Motor is a 1999 carb Johnson v6 150hp. Top speed is 41.5-43 mph at 5300-5400 rpm. My motor redlines at 5500. I don't know if the gearing is the same as yours or not. I'm surprized you're not getting a couple extra mph out of yours, but I don't think the OMC aluminum props are very good in terms of top speed. As you know, this flat bottom, light weight boat is easily driven in terms of planing speed to 35mph or so. But because the boat does not lift out of the water at high speeds the way many modern hull designs do, it seems to me that the boat doesn't want to go much over 40mph unless a lot of horsepower is applied. I think to get this hull to 50 mph you need 200hp or more. But given that the boat is not very comfortable on anything but flat calm water over 40mph anyway, I don't see the point in maxing out top speed on this hull. (I think a 115 would probably be enough hp for easy cruising at 25 to 30mph, which is the boat's sweet spot in my opinion). If you could borrow a Stilleto 15 or 17 pitch, I think you would see a couple mph improvement on top end. But I know you have kept an aluminum prop due to rocks in your boating area. I assume the motor is out of whatever "break in" period that is programmed into its chips? Is it possible that the rpm's might increase over time slightly once the motor is out of "break in" mode??
Peter	posted 10-26-2006 09:04 PM ET (US) The 60 degree carbureted OMC 150s have a reputation of being pretty strong motors so I don't think that the E-TEC 150 would be good for a few extra MPH over one of those. Seems to me that Jay's results are consistent.
JayR	posted 10-27-2006 10:33 PM ET (US) I've only 20 hours or so on it. That's only about 10% of the use I expected for the summer..... I suspect it is still in the break-in period at this point. Hopefully I'll have her out again this week. Thanks, I'll give it some time before making any changes.