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  Prop selection- 97 21' Outrage 250 EFI Merc

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Author Topic:   Prop selection- 97 21' Outrage 250 EFI Merc
rtk posted 03-11-2004 06:14 PM ET (US)   Profile for rtk   Send Email to rtk  
I am repowering my 1997 21 Outrage with a 2003 Mercury 250 EFI. The motor I am replacing is a 1997 Mercury 225 carb. It has a 19P Laser II stainless that I can use but I have been told that the LaserII may not be the best design for the boat- made for lighter/smaller boat applications. Besides that, the size may not work out.

I used the Mercury prop selector and I am getting vey different results (performance, prop type and pitch) based on the "boat type" I choose-"fiberglass fishing" or "offshore fishing".

Weight estimated based on:

Dry Boat Weight: 2500
Motor: 500
Full Fuel (120 gal): 900
T top (hard top) 250?
Misc gear, etc 500?

Total 4650

BoatType: Fiberglass Fishing
Performance Goal: Overall good performance
Boat Weight: 4700.
Estimated Top Speed: 52.9
Theoretical Pitch: 20.0
Black Max - Best economical all-purpose aluminum propeller (48-832832A45) Pitch: 21.0 (RH)
Laser II - Best bow lift & top speed for light boats (48-16546A46) Pitch: 21.0 (RH)
Tempest Plus - Best bow lift & top speed for heavy outboard boats (48-825862A47) Pitch: 21.0 (RH)
Trophy Plus - Quick hole shot, great handling, good top speeds (48-825934A47) Pitch: 21.0 (RH)
Vengeance - Great general boating prop, 5X more durable than A (48-16318A46) Pitch: 21.0 (RH)


BoatType: Offshore Fishing
Performance Goal: Overall good performance
Boat Weight: 4700.
Estimated Top Speed: 47.9
Theoretical Pitch: 18.0
Black Max - Best economical all-purpose aluminum propeller (48-832830A45) Pitch: 19.0 (RH)
Laser II - Best bow lift & top speed for light boats (48-16544A46) Pitch: 19.0 (RH)
Mirage Plus - Excellent speed for high horsepower (48-889620A46) Pitch: 18.0 (RH)
VenSura (Offshore) - Water sports and sgl/twin light C-Consoles (48-825900A46) Pitch: 19.0 (RH)
Revolution 4 - Acceleration, mid-range cruising and top speed (48-857026A46) Pitch: 19.0 (RH)
Vengeance - Great general boating prop, 5X more durable than A (48-16316A46) Pitch: 19.0 (RH)

I want to go with a stainless.

I know the site is just a general guide. My dealer will work with me on propping the boat on the water with an appropriate prop- just wanted to get the expert's opinions.

I know this is long but I wanted to throw all the facts out there.

Thanks in advance!
Rich

jimh posted 03-11-2004 08:24 PM ET (US)     Profile for jimh  Send Email to jimh     
Looking at your results I have seen something that I didn't notice before: the Mercury propeller calculator must allot a particular "hull factor" value based on the TYPE of boat you indicate. In the results above when the weight is held constant and the boat type varied, the "offshore" boat goes slower than the "fishing" boat. This probably reflects an estimation of the hull factor in the speed calculation (which is based on horsepower, weight, and hull factor). An "offshore" boat would probably be considered to have a deep-vee hull and thus a lower hull factor index than a "fishing" boat, which would be a moderate vee-bottom.

My simplistic understanding of these various Mercury propeller lines is limited to relationships like that between the Black Max and the Vengeance. I see those as similar designs just made in different materials. The Laser II has more rake and cup to the blades. If you have a boat capable of doing 45-MPH or more I am sure the Laser II would be a good propeller.

I am certain others can comment with much greater authority on this topic and I hope they do.

rtk posted 03-11-2004 09:11 PM ET (US)     Profile for rtk  Send Email to rtk     
Jim I think your comment on the "offshore" and "fishing" boat classification is right on the money. I would tend to lean toward the "offshore" classification as appropriate for this boat. I have only owned the boat since the end of October 2003 and put about 15 hours on it. With the LaserII top speed with light load (1/4 tank fuel, 2 people, light wind, calm water) was about 45 mph per gps at 5200 max rpm. She was sluggish out of the hole but performed well on plane. Handling though in a bit of current and chop seemed to be a bit sloppy- I did not feel like I had great control of the boat.

I think you are also on the money regarding the prop.

From the Mercury website:

LASER II
If you like to run fast and light, the Laser II is your propeller. A three-blade stainless steel design providing amazing bow lift for high horsepower light weight outboard powered 15' - 18' and sterndrives up to 22'.

For outboards 75 hp and up and Alpha Sterndrives 3.0L - 5.7L
High-rake design for greater bow lift
R/H and L/H rotation (19" - 26" pitch)
PVS-equipped
Equipped with Flo-Torq II hub system

Maximum top speed is not my top priority- handling in seas and midrange performance is. I am going to use the boat a majority of the time for inshore fishing- a couple people on the boat, full fuel, ice and fishing gear (plus a bunch of fish!) is going to add a bit of weight. Don't get me wrong I like a fast boat as much as the next guy but as you all know this is not designed to be a high speed boat.

Thanks again for your interest and your comments.
Rich

VMG posted 03-17-2004 11:59 AM ET (US)     Profile for VMG  Send Email to VMG     
I owned an OR 21 with a '98 Yam 225 EFI. No t-top, it ran 47 mph at 5500rpm trimmed, two adults, 2/3 a bag of gas. Would do 50 w/ light fuel load and one person aboard. Would jump on plane in about 2 seconds without going to full throttle, and it averaged about 3.2-3.3 mpg anywhere between 3000-4000 rpm (25-35 mph). Prop was 15.5x17 Mirage Plus. I have M+ props on newer OR 23 w/ twin 150s and have seen similar benefits in hole shot and mid-range performance.
jeep9221 posted 03-17-2004 04:13 PM ET (US)     Profile for jeep9221    
Take a look under the PERFORMANCE forum for the following - last updated (as of today anyway) on 2-6-04 w/ the following heading:

New 225-HP, 4-stroke Yamaha--1993 Outrage 21

You will find a prop chart based on testing 5 props on my new Y/O-21. I hope that this helps. Top speed has been a consistent 46 MPH, without loosing acceleration w/ a 17 (P) x 15.25 (D) - SS Salt Water Series Yamaha 3 blade prop - my final selection.

rtk posted 03-17-2004 05:05 PM ET (US)     Profile for rtk  Send Email to rtk     
VMG and jeep9221,

Thank you- both your replies are very useful to me. Explains why I was only getting 5200 rpms out of her with a 19 pitch prop. Looks like the 17 pitch is the one for this boat with a 225 HP. The mirage was also recommended by the person who reconditioned my LaserII last fall.

They are supposed to pick up the boat this Friday for the repower. I think I'll start with a 17 or 19 pitch mirage- I am putting a 250 HP on it and it will be interesting to see how much of a difference the extra 25HP makes in performance. I will see what the dealer recommends also.

Thanks again for your replies. I'll post a "performance report" when she is broken in!

Rich


VMG posted 03-17-2004 07:32 PM ET (US)     Profile for VMG  Send Email to VMG     
At the time I bought the boat I was told the Yam SWS props are very similar to the M+ in performance. Deciding factor in this instance was significant price difference. Note the mid-range performance of the SWS prop compared to the others of similar pitch (on Jeep's chart) -- all that diameter (and cupping) pushes alotta water.

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