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1996 outrage 17 repower command thrust 115
Ianuk	#1  Posted on 01/15/21 - 1:19 PM
Member Posts: 3 Comments: 0 Joined: 01/14/21	Hello all, I have a 1996 outrage 17 II which previously had a 1995 Mercury 115 2 stroke. Having just sold the 2 stroke I shall be repowering with a new Mercury 115 4 stroke command thrust. I would like to know which propeller would be best. The engine will come with a propeller and I need to specify the diameter and pitch. I am keen to try to get the correct propeller first time to save a lot of cost in buying lots of propellers to try. I have trawled the amazing resources of the internet as far as I can but I can’t yet find anyone else who has repowered this hull with the command thrust model. I chose the CT option as it is suited to heavier boats and should allow me to stay on the plane at lower speeds and should save on fuel at mid range speeds. It also gives greater choice in prop diameters. My situation is thus: The boat will weigh just under 1 ton with the engine. I will rarely carry more than 100 litres of fuel and my young family currently weigh in at around 220kgs, although this will increase over the years. I would mainly like to cruise at around 18-22kts and would be unlikely to need the top speed to be in excess of 35. The boat had a tendency to porpoise above the mid twenties and I would imagine would be an uncomfortably exciting ride at 40kts! I would like to tow donuts and do waterskiing occasionally (mono ski if the boat will cope) and would love it if I could stay planing slightly slower than previously (16kts ish) The previous 2 stroke performed quite well in most respects apart from fuel consumption and had an old stainless prop with no identifiable markings. All I could measure was that it was 14inch diameter. Any help would be greatly appreciated. I note that Mercury advertise an eco enertia large bladed propeller which might do the job?
Phil T	#2  Posted on 01/16/21 - 8:30 AM
Administrator Personal Page Personal Album Project Albums Posts: 6994 Comments: 6 Joined: 03/26/05	Welcome to WhalerCentral Ian. As you know, the Outrage 17 II is a post-classic designed model with a dry weight of 1700 lbs. It has a min hp of 90 and a max hp of 150hp. The Mercury 115CT has a WOT rpm of 6,000 and a gear ratio of 2.38. For your boat and motor I would estimate a target speed of 43. Note this is for prop calculation requirements, not that I expect you to go this fast in the Channel, North Sea or the Irish Sea. I use 5% for propeller slip. Using a prop calculator, entering all this in, it returns a recommended pitch of 19". It is worth noting the Enertia prop is one of the more expensive props on this side of the pond. ~ $750 - 800 USD What are your prop brand and model options? Can they get you a Mercury Mirage prop in 19-23" of pitch? Where are you located in England. 1992 Outrage 17 I 2019 E-TEC 90, Viper 17 2+ 2018 Load Rite Elite 18280096VT
Ianuk	#3  Posted on 01/16/21 - 12:56 PM
Member Posts: 3 Comments: 0 Joined: 01/14/21	Thanks for taking the time to provide that comprehensive answer Phil. I live on the south coast of the uk in generally quite protected waters but it is very tidal, and with the wrong wind directions the sea can be quite short and choppy. Luckily the outrage is a relatively dry ride compared to other boats. 19 inch pitch seems very reasonable. I am guessing that’s for a 14 inch diameter. The gaps in my knowledge relate to the relationship between prop diameter and pitch. Obviously a larger prop would be harder for the engine to rotate at any given pitch? Is there any advantage for me to use a larger prop with less pitch? The only reason I mentioned the enertia was the advertising blurb and the fact it is larger diameter. It is really expensive! I imagine I will only be offered a run of the mill standard aluminium type prop but now you mention it I will ask the supplier. If I were to invest in a stainless one at any point it would more than likely be a good condition used one.
Phil T	#4  Posted on 01/16/21 - 1:33 PM
Administrator Personal Page Personal Album Project Albums Posts: 6994 Comments: 6 Joined: 03/26/05	Ian - Prop diameter is typically set by the gear ratio of the lower unit. Stainless steel props are recommended as more durable, less flexing, better efficiency. Installing an aluminum prop on a new engine is like buying a Jaguar I-Pace and installing rims from a Austin Metro. Your 115hp is in the middle of the hp range for the Outrage 17II. Add that you want to pull a tube or skier and that tells me you should consider a 4 bladed prop. This will help you with a lower planing speed and also increase ability to maintain plane. To go from 3 to 4 blades, one typically drops 2" of pitch from the 3 blade size. I would ask your dealer for 2-3 prop make/models with diameter/pitch in both 3 and 4 blades from the dealer. I can do some research, talk to a few Outrage 17II owners and prop gurus to give you suggestions. I have a few whaler owner friends in the UK. Three in and around Poole/Bournmouth, one in Wales and another in Norfolk. Edited by Phil T on 01/16/21 - 1:48 PM 1992 Outrage 17 I 2019 E-TEC 90, Viper 17 2+ 2018 Load Rite Elite 18280096VT
Ianuk	#5  Posted on 01/21/21 - 3:07 AM
Member Posts: 3 Comments: 0 Joined: 01/14/21	Having spoken to the supplier my propeller option is for a standard 3 bladed aluminium. I think if I get one and I feel that it is a good diameter and pitch and I am able to meet the wot targets etc, then I would keep an eye out for a replacement used stainless one of the same dimensions. You mentioned that prop diameter is governed by the gear ratio, but I have also read that for efficiency I should swing as large a prop as possible and adjust the pitch accordingly. You mentioned that I should consider a 4 bladed prop as this would give more blade area and better grip etc (and drag too). I understand that most outboards will be limited with blade diameter and so might have no choice but to increase to four or five blades for increased area, but surely a larger 3 bladed prop (up to 16 inch I think with the ct) would have the same effect? Sorry if I seem to be confusing things but I am keen to learn as much as I can!
Phil T	#6  Posted on 01/21/21 - 6:45 AM
Administrator Personal Page Personal Album Project Albums Posts: 6994 Comments: 6 Joined: 03/26/05	I would respectfully disagree with the recommendation for an aluminum propeller. Less efficient More flexing damage easily. See comment above about tires and rims. Please paste the link to what you are reading so I can follow along. What are your prop brand and size options from your supplier? Edited by Phil T on 01/21/21 - 6:48 AM 1992 Outrage 17 I 2019 E-TEC 90, Viper 17 2+ 2018 Load Rite Elite 18280096VT
biggiefl	#7  Posted on 01/21/21 - 7:37 AM
Member Posts: 890 Comments: 4 Joined: 05/08/06	IS the prop being supplied by the shop repowering it? If so that would explain the aluminum choice. Ask if you can upgrade or take it and when you buy a SS prop, keep the aluminum as a spare. I will not run an aluminum prop on anything over 30hp. 24 Whalers so far....
guitarfish	#8  Posted on 01/22/21 - 1:53 PM
Member Posts: 175 Comments: 2 Joined: 04/24/10	I am surprised by that answer biggie, not that I disagree. I have never had a stainless prop so I am the polar opposite. I may get one on my latest Whaler when I get it sorted out. 1971 Menemsha 16 and 1978 15' Custom