Changing stock prop on 2004 Johnson 50HP, Update :-(

[Salmonseeker]

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 11 3/4 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.<br />Thanks in advance

 

[Dhadley]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

Work with your existing prop to max out the set up before you spend $$$ on another prop. For maximum engine life you want your top rpm around 5800-6000 with an average load. Try raising the motor to gain rpm and see how the motor reacts. This will give us a better picture of which ss prop to get.

 

[ob15]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

Listen to Dhadley, he's the expert. <br /><br />The setup doesn't sound right. I have a 15' skiff with an 89 50 on it and I can hit the rev limiter on my motor (6100) using the same prop (11 3/4 x 17). I can get over 40 mph on mine too. How heavy is the boat and is it a vee hull?<br /><br />Where is the AV plate in relation to the keel? As Dhadley said, try raising the motor on the boat.

 

[Dhadley]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

Hey Dave -- sell Mr Fisherman38 your 17 and we'll fix you up with a 19. <br /><br />I see a faster boat in your future.........

 

[Ron G]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

 

[ob15]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

I actually have a 19" SS prop but the hub is spun. I'm not sure if I want a SS prop on the motor though. Have heard the lower units weren't really designed for the stresses from a SS prop.<br /><br />Enough of me, lets help Mr. Fisherman38.

 

[Dhadley]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

Trust me -- a ss prop doesnt put any stress on a lower unit that it cant handle. We've run ss props since they came out. On the gearcases of the day.<br /><br />If you want a ss prop -- get one. No reason not to.

 

[ob15]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

Thanks a lot Sir Dhadley. I will definitely get a new hub put in the SS prop. It's actaully a 11 1/2 x 19. Should work out great.

 

[Dhadley]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

Sounds good. Keep us posted on the progress.

 

[ob15]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

will do.

 

[Salmonseeker]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

Hey guys. Thanks for the quick response. The AV plate is about 1" above the keel. The boat is a 2004 Crestliner 1600 SC v bottom, the boat specs say it weighs 860lbs. I am not sure I want to raise to motor because during tight turns or larger waves if the tilt is not near the lower limit the boat cavitates and over revs. I then have to let off the throttle and allow the prop to grab. <br />One other thing I am concernI have with my prop, I went to the Johnson website and check out their props. It says my prop(hydrus high thrust prop) is designed and manufactured for pontoon boats or work boats. Check it out for yourself. <br /> http://www.evinrude.com/en-US/Accessories/Product.htm?product=HYDRUS&category=Propellers <br />Perhaps I just need a different style prop and not change the pitch. WIll pitch affect my speed?<br />Thanks JASON

 

[Dhadley]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

We dont worry too much about venting in a tight turn with aluminum props if youre going to ss anyway. The better design will take care of that.<br /><br />Right now we are only concerned about how the set up reacts to increases in X dimension. If you raise the motor and gain rpm then we know which direction to go when looking at ss props. If the r's dont come up we know that hull doesnt respond well.<br /><br />On the other hand if youre not going to change X dimension then the only way to get the correct rpm is with pitch.

 

[Salmonseeker]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

If I do go with a smaller SS pitch prop say a 15 which should bring my rpm up. How will this affect my top end speed. Will it improve any?<br />Thanks JASON

 

[mollywalk]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

I have a 12 1/2 x 15 alum and a S.S. The speeed will not change much if any. Getting out of the hole will. A 15 pitch will increse your RPM's around 400 so I will first try a 12 1/2 x 15 alum as they are cheaper.<br />I was able to find a use S.S. on ebay after watching for a long time for a very good cheap price.<br />I had to remove a lot of rust and paint but it works great.<br />I sanded after useing removel and etch price and than engine high gloss paint.<br /><br />Try that.<br />A show room S.S. is a lot of money.

 

[Salmonseeker]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

I know they are expensive but I have found a great price on one. Unfortunately they won't let me try it. I juat wanna make sure it will help before I purchase it.<br /><br />Dave F. I would love to get 40 mph. where is your AV plate in relation to the hull bottom.<br />If you got any pics that would be great.<br /><br />Thanks Jason.<br />ps sorry about the dupilcate post

 

[Dhadley]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

This is why you need to test with your prop. You need to know how the rig reacts to change.<br /><br />If you dont want to test, buy the smaller of the two props. Youre much better off adding bite than trying to remove bite from a prop.

 

[ob15]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

My AV plate is slightly over an inch above the keel. Maybe 1 1/2" max but propably about 1 1/4"

 

[Salmonseeker]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

Dhadley,<br /><br />You said my max rpm should be 5800-6000 rpm for long engine life. My owners manual says 4500-5500 rpm. Are these numbers only conservative estimates? Will my engine last running 5800-6000 rpms. <br />Thanks for all yout help <br />JASON

 

[Salmonseeker]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(

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. Top speed was about 29 MPH.<br /><br />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 with Cavitate.<br /><br />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.<br /><br />If I stay with the same Rapture prop it seems like I might almost need a 19 pitch prop.<br /><br />I defenatelly want a new prop and want my current one to be a spare. Any help picking one would really help.<br /><br />As for the Rapture I know a guy who wants it so its no loss to me.<br /><br />Thanks Jason

 

[Salmonseeker]

Re: Changing stock prop on 2004 Johnson 50HP, Update :-(