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Bennington 18.5 with 50hp Johnson 4st Need Prop

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Fox5flyer

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My 2004 pontoon matching 50hp Johnson 4st is over propped. Currently has 11.8x11p Solas and only achieves 5200rpm WOT lightly loaded when I should be getting at least 6000 or a little more. Can anyone out there who has this combo tell me what they are using for a prop please? Aluminum or SS.
Thanks,
Darrel
 
I had that same engine on a '03 Harris 22' but it's long gone. There really isn't any performance benefit to put a SS prop on a 50 hp though.
 
Echoing Tom above. No use putting a SS on a 50hp. They are only worthwhile if you have a high HP motor because the SS wont flex and lose performance thrust at high HP speeds, whereas an aluminum prop will.

IMHO go aluminum for that motor. Cheaper. Safer on your lower unit if you hit something with it. It wont flex or lose performance with a 50hp motor.

As to specifics, I don’t know for that motor and hp what size, pitch or brand. Have you tried looking up ideas with a prop selector? Also, hopefully some others with 50hp motors will chime in too.
 
My thanks to Tom and Jeff for the responses. Every bit helps. I tend to agree that SS is not necessary so long as I don't hit something, but a lot of people swear by them. I've found on ebay a new/old stock aluminum 11.25x10p that is priced right and I might give it a go and if it doesn't work I'll just add it to my growing collection. This whole thing with pontoons is a new world for me. I never realized how heavy and draggy they are which means more hp needed and being able to transfer that hp to the water with the right prop. My motor's manual calls for a 12x13p which might be ok for a speedy boat, but for a pontoon that is way over propped, as I found out.
Hopefully someone with the same setup as me will chime in.
Thanks, again.
Darrel

Vikingstaff said:
Echoing Tom above. No use putting a SS on a 50hp. They are only worthwhile if you have a high HP motor because the SS wont flex and lose performance thrust at high HP speeds, whereas an aluminum prop will.

IMHO go aluminum for that motor. Cheaper. Safer on your lower unit if you hit something with it. It wont flex or lose performance with a 50hp motor.

As to specifics, I don’t know for that motor and hp what size, pitch or brand. Have you tried looking up ideas with a prop selector? Also, hopefully some others with 50hp motors will chime in too.
Click to expand...
 
Where stainless shines is holding its shape while under power. The 50 does not have enough force to flex the aluminum prop, thus you are not leaving anything on the table. And any boat with 50hp will be doggy. Just keeping it real with you.
 
lakeliving said:
And any boat with 50hp will be doggy. Just keeping it real with you.
Click to expand...
I understand that. I've been around the block a bunch of times and I've watched how horsepower keeps growing to the point that it's no longer about what is necessary, but how fast can you go and how much gas you can burn in a very short time, especially with pontoons!
Personally, 50hp is plenty for my boat and I just want the benefit of all my motor has to offer and that is centered on the prop.
Thanks,
Darrel
 
I have a Yamaha 50Hp 4ST, does OK by me!!! Who needs to go fast in a pontoon??? When I am on mine I am NOT in a hurry to do anything!!!
 
Fox5flyer said:
I understand that. I've been around the block a bunch of times and I've watched how horsepower keeps growing to the point that it's no longer about what is necessary, but how fast can you go and how much gas you can burn in a very short time, especially with pontoons!
Personally, 50hp is plenty for my boat and I just want the benefit of all my motor has to offer and that is centered on the prop.
Thanks,
Darrel
Click to expand...
That's cool that the 50 HP works for you and that's fantastic! We have enough HP to do what we want (skiing, wakeboarding, tubing, trying to outrun a pop up storm) but we don't go flying around the lake WOT. The HP is there if you need it. We spend most of our time anchored in a No Wake zone cove floating/eating..........

Quick story........We were on a neighbors 20 foot Sweetwater pontoon boat with a 75 HP Yamaha on the back. We were on a different part of the lake hanging out about 7 miles away. Well we saw a storm moving in and we packed up and took off for home. 4 people, 2 coolers, gear, towels, etc.............The wind and sideway rain caught us and was stinging us as it hit. He had the throttle mashed down. I looked over his shoulder and we were doing a whopping 12 MPH!!! Couldn't get out of our own way. By the time we got home the sun was coming out........
 
Another thing to keep in mind is SS is A LOT heavier than aluminum. I have both props and estimate my SS (thanks Todd!) is 3 or 4 times the weight.

A small motor will have to turn that extra weight. Acceleration could suffer. Speed could suffer. Gas mileage could suffer. You might be worse off with stainless... Just something to consider.
 
I'll tell you what I have but don't think it will help after looking at your current prop's specs. Yamaha T50 on a 20' with a Quicksilver 14x11P (p/n 2030P11). The T50 has an oversized lower end and has no trouble spinning that size prop. It's been a while since my tach worked but when it did I recall seeing about 5800 rpm.

Since your boat is older like mine, I'll ask if the toons are clean? Like, shiny polished clean? If you're dragging around years of growth with you the motor will be working harder and the max rpm will suffer.
 
"Since your boat is older like mine, I'll ask if the toons are clean? Like, shiny polished clean? If you're dragging around years of growth with you the motor will be working harder and the max rpm will suffer."

Thanks, Maynard! :)
Every bit of input helps and I'm hoping that I'm homing in on this problem. I've said I wouldn't buy another prop and to stop using the Trial and Error method which can build up quite a collection for eventual ebay fodder. Actually, to many people it's not a problem at all, as I'm sure they don't really care about how fast the boat will go or what WOT rpm it will get. The guy I bought it from said he never ran it WOT and had no idea what his max rpms should be! I don't plan on cruising that way, but it's good way, IMO, to determine if you have the correct prop hooked on.
As for the condition of my tunes, honestly no they are not polished clean and shiny so I'm sure it is having some effect on this, but then again they aren't bad or beat up and I'll live with them the way they are. When I'm in chest deep water I have a scrubber that I use to give them a good clean.
Anyway, when the new prop gets here I'll test it out and report back.
Darrel
 
Fox5flyer said:
What prop, D/P, brand, model are you using? Also, what is your WOT?
Thanks,
Darrel
Click to expand...
I actually don't know the specifics, I have a Yamaha 50Hp my WOT is just north of 5500.
 
Thanks, I had no idea when I got into this what a "black art" it is. Specifics are so important.
However, I think I've found the right prop, but awaiting it's arrival. Will report back with my success, or not.
Darrel
Jim Rampello said:
I actually don't know the specifics, I have a Yamaha 50Hp my WOT is just north of 5500.
Click to expand...
 
Fox5flyer said:
Thanks, I had no idea when I got into this what a "black art" it is. Specifics are so important.
However, I think I've found the right prop, but awaiting it's arrival. Will report back with my success, or not.
Darrel
Click to expand...
I have seen all kinds of problems with props and WOT RPM's on here. Makes me feel pretty good that mine is where it should be, I think!
 
Maynard G. Krebs said:
I'll tell you what I have but don't think it will help after looking at your current prop's specs. Yamaha T50 on a 20' with a Quicksilver 14x11P (p/n 2030P11). The T50 has an oversized lower end and has no trouble spinning that size prop. It's been a while since my tach worked but when it did I recall seeing about 5800 rpm.

Since your boat is older like mine, I'll ask if the toons are clean? Like, shiny polished clean? If you're dragging around years of growth with you the motor will be working harder and the max rpm will suffer.
Click to expand...

Thanks, Maynard G Krebs. I'm sure that's your real name? -:)
First off, no barnacles on my toons, but some slime and a thin layer of rough stuff which I'm sure contributes parasitic drag to a degree. I clean it up as much as I can whenever I'm parked on the submersed sandy point about chest deep, but other than a towel I need something a bit more robust like a large, durable scrubbing pad. Any suggestions?
Now, on to the prop. I received my 12.25 X 9p aluminum unit (new) and now I get right at 6500 WOT which is the max recommended rpm (5900-6500) for my engine (Johnson 50hp 4str). I should be happy with that as it gets there quickly, but I tend to be a perfectionist with most of my time spent cruising 6000 would probably be much better for a compromise. So for the time being I'll be happy and just keep my eye open on Ebay for maybe a 10p or maybe a touch larger on the diameter. Again, input welcome.
Anyway, folks. Thanks for all of the input as I appreciate it immensely and I'll keep an eye on this forum and if I can contribute anything useful I'll chime in.
Regards,
Darrel
NE Michigan Lake Country
 
Sounds like you are more or less set, aside from a small tweak to it all. Glad to hear it! Also noticed you are boating in NE Michigan. Any one particular lake or a cluster of them? A decent amount of us Michiganders around here. We are on Houghton Lake ourselves.
 
Vikingstaff said:
Sounds like you are more or less set, aside from a small tweak to it all. Glad to hear it! Also noticed you are boating in NE Michigan. Any one particular lake or a cluster of them? A decent amount of us Michiganders around here. We are on Houghton Lake ourselves.
Click to expand...
I'm on Cedar Lake, just north of Oscoda on the east coast about 30 miles south of Alpena. It's about 6.5 miles long x 3/4 mile wide. Nice lake, but would be nicer if deeper.
D
 
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