Will changing from factory aluminum prop to SS aftermarket increase rpm's

Salmonseeker · Aug 16, 2005

Hi guys, I want to upgrade to a stainless steel prop. I have a 2004 Johnson 50HP 2 stroke on 16 foot aluminum. My current prop is a 12 1/4 X 17 stock aluminum prop. With this set up I run 30 MPH at 5100 rpm. The max rpm range is 5500 rpm. I want a bit more speed out my boat. Will a SS prop increase speed? or RPM?,or should I change the pitch to 15. Thanks in advance JASON

roscoe · Aug 16, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

SS will scrub a few rpm. Drop to a 14 or 15. Should put you at 5500-5600, and your motor will love you

Salmonseeker · Aug 17, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Thanks Roscoe, How do you think this will affect my performance. Top speed, hole shot,etc. I should also note my current prop says it is designed for high thrust use on pontton boats and work boats. Check it out. http://www.evinrude.com/en-US/Accessories/Product.htm?product=HYDRUS&category=Propellers Thanks Jason

roscoe · Aug 17, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

If you ar eworried about losing top end speed, don't. Any loss in speed due to the prop pich will be overcome by the increased rpm you will be turning. Hole shot and top speed should both be a little better. But it depends on which ss prop you go with.

ob15 · Aug 17, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

fisherman38. Try to only post once per topic. Can get very confusing to some while going through the forum. Thanks. Duplicate post

Solittle · Aug 17, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Whqat is your set-up? - - Where is your cavitation plate relative to the bottom of the hull? You might be able to pick up some rpm by raising the engine.

Salmonseeker · Aug 17, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

It is about 1" above the center of the hull bottom. JASON

Salmonseeker · Aug 18, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Thanks for the help guys, Roscoe I got a great deal on a new Michigan Wheel Rapture 11 3/4 x 15 SS prop. Going on holidays for a couple of weeks, will try it out as soon as I get back. I can't wait. Thanks JASAON

Salmonseeker · Sep 11, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Hi again guys took the boat out today with a new prop. I used a 11 3/4 X 15 Michigan wheel Rapture SS propeller. As soon as I gave it full throttle the rpms would hit around 5000 then I would max out at about 6100 rpm(possibly hitting the rev limiter). Top speed was about 29 MPH. I put the old one back on, It is a Johnson stock prop 12 1/4 X 17 and it definately sounded better. Ran 31 MPH at 5100 rpm. With the engine fully trimmed I could hit 5350 rpm and gain 1 MPH, however any slight movement of the steering wheel or minimal wave and the prop would ventilate. I was hoping by dropping a pitch my rpms would be near what was recomended, 5800 rpm. Obviously the different style prop makes a difference. If I stay with the same Rapture prop it seems like I might almost need a 19 pitch prop. Any help picking one would really help. Thanks in advance, Jason

roscoe · Sep 11, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Well thats a fine mess

Yes, there is quite a difference between different props, beyond the dia and pitch. I'm not very up to date on the differences in the SS props available. But there are many post here that compare the differences in performance between 2 or 3 ss props.

walleyehed · Sep 11, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

The fact you can run with full trim indicates the engine is mounted too low on the transom. Let's stay with the alum 17 if it's in good condition. Lift the engine one hole and test. At this point, speed isn't important, let's get the efficiency up and the speed will come with it.

Salmonseeker · Sep 11, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Thanks guys, Dhadley also recommended this in another post. I will raise the motor up one hole and try it later this week. I was thinking about doing this as some water does flow over the cavitation plate. I will keep you guys posted. Jason

Scali · Sep 11, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

I'm not trying to sound like a jerk but on a 16' skiff with a 50, why bother with a SS prop ? I lost a lower unit when my 19' Carolina Skiff with a 90 johnson once hit a slab of cement near the ramp { had a SS prop }. Dont get me wrong, SS props are great & have thier place but for a small fishing skiff that hit's the shallows, geeze I'd stay with aluminum . Unless your sure it's all soft bottom & no rocks { if thats possible } & or have the proper insurance.. Oh well, just a thought..

dmonwai · Sep 11, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Originally posted by Scali: I'm not trying to sound like a jerk but on a 16' skiff with a 50, why bother with a SS prop ? I lost a lower unit when my 19' Carolina Skiff with a 90 johnson once hit a slab of cement near the ramp { had a SS prop }. Dont get me wrong, SS props are great & have thier place but for a small fishing skiff that hit's the shallows, geeze I'd stay with aluminum . Unless your sure it's all soft bottom & no rocks { if thats possible } & or have the proper insurance.. Oh well, just a thought..

I also have a 16 foot aluminum boat with a 50hp main motor. I put a SS prop on because I wanted the most performance I could get from my setup. My boat weighs about 1700lbs loaded up with me and my fishing gear and a full tank of gas (18 gallons). When I first got the boat it would do 27-28 MPH by GPS, after changing motor height, changing to a SS prop and adding Smart Tabs it now does 32-33 MPH. It also handles and rides a lot better, I'm happy with the improvements. But I might add a hydraulic jack plate next because I know I can go higher on motor height, right now I'm at the highest I can go without drilling new mounting holes in the transom. The shallowest water I'm in is when I'm at the ramp. I fish salt water for salmon and the water depth I fish in is anywhere from 100 feet to 700 feet deep. When I'm fishing I don't use the main motor, I use a kicker to troll. My main motor is only used for getting to/from the ramp and fishing areas.

walleyehed · Sep 11, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

If running shallow water, ya gotta operate the boat accordingly...I would only recommend staying with alum. if you run in rapid type rivers with alot of boulders in which case a jet-drive would be the prefered means of propulsion. Much more lower unit damage occures from bent, dinged, mangled alum. props putting undue stress on the lower unit gears because the prop gave insted of the hub allowing the bent prop to continue to be used......SS on the other-hand, if a direct hit occures, the hub will slip 9 out of 10 times...Re-hub and go.

Salmonseeker · Sep 11, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Hey guys thanks for the response, I wanted to go from Aluminum to SS because I was told I would get more performance. Never really thought about hitting anything, I will definatelly keep it in mind. Most of my fishing is done on Lake Ontario for Salmon, fishing mostly deep water. I do occasionally fish new smaller lakes so hitting bottom is a possibillity. I may stay with aluminum, just experimenting right now. Damon my set up sounds similiar to yours especially if that picture is your boat. I got a couple of Scotty electric downriggers etc. I do not have a trolling motor however, I just troll with my main. It actually trolls for salmon well. I can troll as slow as 2 MPH. Would love a small kicker for trolling, especially for as a back up. I venture far from shore some days and would hate to have no back up motor if mine failed. Just curious what size of trolling motor do you use? The motor is mounted in its lowest position right now. I will try to raise it one hole and see what happens. Thanks Jason

Salmonseeker · Sep 11, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Good point Kenny. I have had aluminum props in the past and they don't take much to damage. Jason

dmonwai · Sep 11, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Originally posted by fisherman38: Damon my set up sounds similiar to yours especially if that picture is your boat. I got a couple of Scotty electric downriggers etc. I do not have a trolling motor however, I just troll with my main. It actually trolls for salmon well. I can troll as slow as 2 MPH. Would love a small kicker for trolling, especially for as a back up. I venture far from shore some days and would hate to have no back up motor if mine failed. Just curious what size of trolling motor do you use? The motor is mounted in its lowest position right now. I will try to raise it one hole and see what happens. Thanks Jason

I have a Honda 8hp for a kicker. I use a connecting bar to the main motor so I can steer from the helm and use a Trollmaster throttle control on it. It works really well for me, I fish by myself 99% of the time. I really like having a kicker, it keeps the hours off my main motor (I'm on the water fishing about 50 hours a month)and it great to have in case my main motor has problems. Sometimes I'll be 20-25 miles from the launch where I'm fishing. My boat is a 2001 16' Smokercraft Osprey. I have 3 Scotty electric downriggers (2 mounted and 1 spare), Lowrance X107CDF fishfinder, Garmin 276C GPS/Chartplotter, Pro-Troll Blackbox, Icom 402S VHF. I fish all over Puget Sound and the Strait of Juan de Fuca for salmon. Here is a pic from a salmon derby on the Strait of Juan de Fuca last year.

Scali · Sep 12, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Wallyhed, are you trying to tell me the hub will slip 9 out of 10 times when a direct takes place with a boulder using an SS prop resulting in no damage ??????? If so I respectfully disagree emphatically. The propshaft spline twists more often then that, happened to me, seen it over the years @ the Marina a few times. I just dont believe thats true..

walleyehed · Sep 12, 2005

Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's

Believe what you wish...I test props as a part of my living. I will run more props in 1 month than most Marinas change in a year. The rubber hub is designed to slip long before the splines or gears take any heat, BUT, if the gears and splines have not been taken care of as they should be...yes, you can twist the splines, but that is Extremely rare. In fact, in over 25 years, I have not seen a spline twisted from a prop-strike but once, in which case it was a solid hub on a twin Scarab that left the water at about 75MPH, engines over-reved and when the props hit back in the water, it twisted the splines enough we had to cut the props off. "Resulting in no damage to the lower unit"....not the prop...the prop will obviously be damaged, but fixable...aluminum would be trash.

The propshaft spline twists more often then that, happened to me, seen it over the years @ the Marina a few times.

The hub WILL slip before the splines twist. That's why they are made that way. And, as I said, if it does twist the splines (I'd rather think it maybe sheared them), the prop is improperly installed and/or the prop shaft has been neglected.

Will changing from factory aluminum prop to SS aftermarket increase rpm's

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