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1980 15 with 40hp Mercury prop recommendation
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| Tom in VA |
Posted on 09/02/20 - 11:02 AM
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Repowering with 2019 Mercury 40 hp (not Command Thrust). Motor has WOT RPM of 5500-6000 and 2.00:1 gear ratio. In lieu of Black Max aluminum prop, what are recommendations for optimal performance. I saw a previous thread that suggested Stiletto Triad but that was a number of years ago. When I looked online appears this prop is no longer available. Appreciate any suggestions (hoping not to spend a lot!). Thanks!
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| pederj |
Posted on 09/02/20 - 11:24 AM
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I have a similar rig. Mine is a 1975 15’ sport with a honda 40hp fourstroke. It came with a four blade aluminum prop 11.1 x 11. My motor is the same for max rpms and gear ratio. I did experiment with a three blade aluminum prop Solas 11.1x13.
With two men about 400# together, battery, 1/2 tank of gas on flat water we did 34mph at 6000 rpm with the three blade prop, per Lowrance fishfinder. With the four blade prop we did 32 mph. The motor is mounted three holes up.
The four blade prop got us on plane quicker and just felt like a smoother ride.
For this boat, a comfortable cruising speed for me is about 24 mph, which is about 5000rpm and I went with the four blade prop.
Hope this helps.
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| biggiefl |
Posted on 09/02/20 - 12:13 PM
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Just FYI....for maximum longevity for a gas engine, cruise speed should be 75% of redline or less. 5k is about 83.5%. A diesel can cruise up to 90%
24 Whalers so far.... |
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| Phil T |
Posted on 09/02/20 - 12:51 PM
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I don't have any owner recommendations for the 3 cylinder Mercury 40hp Fourstroke and a 15 Sport.
The prop calculator returns a recommendation for pitch as 12.6"
Given Pederj's performance above, I would say 13" is accurate. I would recommend a stainless prop rather than aluminum. Best way to explain aluminum vs stainless is its like buying a 40K car and then putting Big Wheel tires on it.
Typically you drop 2" of pitch from the aluminum/stainless prop pitch size for a 4 bladed prop.
Consider a Mercury Spitfire (4 bladed) 10.6x12 part #8M8026625
1992 Outrage 17 I
2019 E-TEC 90, Viper 17 2+
2018 Load Rite Elite 18280096VT |
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| Tom in VA |
Posted on 09/03/20 - 4:38 AM
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Appreciate everyone’s feedback, a four blade prop wasn’t even on my radar. Looking for clarification on the Spitfire recommendation, am I correct that you are suggesting this as a solid alternative if stainless is too pricey for me? Also you noted that going to a 4 blade usually translates to a drop in pitch by 2 but you are recommending a 12 pitch. Was that a typo or your recommendation? Final item, my plan is to have motor installed 2 holes up as that is what I have seen advocated by most people on Whaler Central. Thanks all!
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| Phil T |
Posted on 09/03/20 - 6:31 AM
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I might have misread your original post in thinking you were looking for a 4 bladed prop. Too many prop threads in my head.
Primary recommendation is for a stainless 3 bladed prop. Select a 4 bladed stainless if you carry heavy load, need a low planing speed.
Would start with Mercury Vengeance 3 blade in 13" of pitch. If you want 4 blade, Trophy Sport.
1992 Outrage 17 I
2019 E-TEC 90, Viper 17 2+
2018 Load Rite Elite 18280096VT |
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| Tom in VA |
Posted on 09/03/20 - 7:45 PM
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Phil, I think I’m going with the Spitfire aluminum 4 blade. Could you confirm the proper pitch? Unsure if you meant 13 for the 3 blade prop or the four blade. Thanks again for your help and patience!
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| biggiefl |
Posted on 09/04/20 - 7:55 AM
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I would say an 11 or 12, definately not a 13 with 4 blade. I personally would not run a 4 blade on a 15' hull.
24 Whalers so far.... |
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| Phil T |
Posted on 09/04/20 - 7:59 AM
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The 13" pitch recommendation is for the 3 blade. Typically one drops 2" of pitch when going to a 4 bladed prop.
I don't recommend aluminum props for several reasons.
Easily damaged.
Don't "protect the gearcase" better than stainless steel. Old wive's tale.
Cost more in the long run, will need to be replaced.
Don't perform as well as stainless steel.
1992 Outrage 17 I
2019 E-TEC 90, Viper 17 2+
2018 Load Rite Elite 18280096VT |
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| Tom in VA |
Posted on 09/04/20 - 3:19 PM
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Once again, appreciate everyone taking some time to share their wisdom (and patience). As it turns out, due to COVID-19, everything appears to be back ordered. I drop off the boat tomorrow for the repower and they’ll stick a Black Max prop on it for now. I’ll see how that performs and then order a “permanent” prop based on what I learn and keep the Black Max as an emergency backup.
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| Tom in VA |
Posted on 09/24/20 - 4:58 AM
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Got the boat on the water for the first time last weekend and am pleased so far. Have only run WOT briefly as I’m in break in period and am seeing it run at 30 mph (confirmed by both my Lowrance and Waze app). Had same top end whether it was me and my buddy or just myself in the boat. Haven’t messed around too much with the trim as this is my first experience with this capability. When I have tried trimming it I think I’ve trimmed up too much as the boat would start porpoising. Boat hasn’t had any difficulty getting up on plane and is burning just under 1 1/2 gallons an hour. Thanks again to everyone for their input.
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| Phil T |
Posted on 09/24/20 - 6:36 AM
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Tom -
Finish break in and then do some performance testing.
Report WOT rpm, speed, engine height, prop make/model/size.
Pictures would be good too!
Thanks
1992 Outrage 17 I
2019 E-TEC 90, Viper 17 2+
2018 Load Rite Elite 18280096VT |
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| Tom in VA |
Posted on 10/31/20 - 1:13 PM
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Completed break in and have the following performance numbers with Black Max 3 blade 10 3/8 x 14 pitch (aluminum):
With just me (180 lbs), full 6 gallon fuel tank...
WOT 6,100* rpm = 33.2 mph; 5,500 rpm = 30.1 mph; 5,300 rpm = 28.5 mph
This was my most recent run, have never seen WOT rpms exceed 6,000 previously.
Performance with 4 people (~600 lbs), full 6 gallon fuel tank...
WOT ~5,600 = ~28.4 mph
Performance with 3 people (~420 lbs), full 6 gallon fuel tank...
WOT 6,000 rpm = 30.1 mph
Other than when carrying 4 people, I have found the boat to get up on plane fairly quick. With four it took some time and required a lot more rpm to maintain plane.
Let the feedback begin!
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| pederj |
Posted on 11/02/20 - 6:01 PM
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Hey Tom,
Earlier in the thread you mentioned mounting the motor 2 holes up. I am just wondering if thats how it ended up. Mine is mounted 3 holes up and I was really concerned it was too high based on my prior boating experience. But it has worked very well with the motor peeing strong and still having lots of “grip” while turning. I should of mentioned in my first post that with a couple bumps of t-n-t at full speed, you will gain another 1-2 mph.
Good luck!
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| Tom in VA |
Posted on 11/02/20 - 6:29 PM
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Motor is mounted 2 holes up (i.e. 3 set of holes). I did just as you suggested with the trim on my last run where I was by myself and it added a couple mph. Thanks!
Edited by Tom in VA on 11/02/20 - 6:34 PM |
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| biggiefl |
Posted on 11/03/20 - 6:44 AM
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Trim till it slips and them bump it down till it grips when doing a WOT run.
24 Whalers so far.... |
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| Tom in VA |
Posted on 11/06/20 - 2:33 PM
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Looking at my results, any recommendations on using different prop?
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| Phil T |
Posted on 11/06/20 - 5:46 PM
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see post 6
1992 Outrage 17 I
2019 E-TEC 90, Viper 17 2+
2018 Load Rite Elite 18280096VT |
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