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Newbie- Prop on 20SLI w/ Yamaha 50Hp motor

acehiggy

acehiggy

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Buckeye Lake, Ohio
I am new to boating with getting my first boat last year. I have a 2010 Bennington 20SLI with the Yamaha 50HP 4-stroke engine. I bought it new at the dealer and have no idea what prop the dealer put on it. It runs about 6000 RPM at full throttle. Does this sound like the correct prop for my setup. I was told max RPM was 6000 and I should never exceed it, is this correct?

Thanks in advance for your input.
 
Hi acehiggy, welcome to the forum! It sounds like you are propped correcly, as long as you don't exceed 6k rpm. I have a 20SLi as well, but only get 5500 rpm. I would like to know what your gps speed is and what prop you have. The numbers are stamped on the prop, let me know what you have! :)
 
Geoffrey & Brenda said:
Hi acehiggy, welcome to the forum! It sounds like you are propped correcly, as long as you don't exceed 6k rpm. I have a 20SLi as well, but only get 5500 rpm. I would like to know what your gps speed is and what prop you have. The numbers are stamped on the prop, let me know what you have! :)
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I will check this weekend and let you know. Thanks for your reply.
 
acehiggy said:
I am new to boating with getting my first boat last year. I have a 2010 Bennington 20SLI with the Yamaha 50HP 4-stroke engine. I bought it new at the dealer and have no idea what prop the dealer put on it. It runs about 6000 RPM at full throttle. Does this sound like the correct prop for my setup. I was told max RPM was 6000 and I should never exceed it, is this correct?

Thanks in advance for your input.
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I have almost exactly the same boat and I get 18mph with a 14x9p Mercury prop on my Yamaha High Thrust 50.
 
That's why i was asking, i have a Yamaha H.T. 50, 14inx13p, 5500 rpm 18mph, i thought if i went down on pitch i would gain rpm & mph?
 
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You should. A 14x12p might get you 20mph. I'm guessing you have 25" logs. (Mine are 23")
 
acehiggy said:
I will check this weekend and let you know. Thanks for your reply.
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I took a look from the dock this morning and without getting in the water, I can't see any labeling on the prop. When my wife get's here this evening, we will try to get a better look.
 
Good thread. Ericscher, I have the same Yamaha and boat as you.[ with the exception of 25" tubes] I go about 19mph at 5200rpm. Good to know I am in the ballpark.
 
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Ace...

Back the boat into the slip and trim the prop up out of the water. You should find the markings you're looking for on the rim of the hub.
 
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Sparky -

I'm looking forward to doing a little, er... performance enhancing.

Add a 22' ESP center tube some extra bracing and a wave shield; then replace my 50hp Yamaha with 20" shaft 225 horse Yamaha on a hydraulic jackplate... Yup. Oughtta shorten that lake right up. :D
 
sparkdr, don't you think 5200 is a little low? seems like you're leaving a little power and rpm behind. what prop are you running? i have the 25" logs as well, and only get 18mph @ 5500. Hey eric, yipes! let us know how those mods turn out for ya! :D
 
Geoffrey & Brenda said:
sparkdr, don't you think 5200 is a little low? seems like you're leaving a little power and rpm behind. what prop are you running? i have the 25" logs as well, and only get 18mph @ 5500. Hey eric, yipes! let us know how those mods turn out for ya! :D
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I will check next time out. I didn't think running at a lower rpm would be a bad thing as long as i'm hitting 18-19 mph.
 
Geoffrey & Brenda said:
Hey eric, yipes! let us know how those mods turn out for ya! :D
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LOL, yeah...

When they finally rise high enough on the priority list. :lol:

What's that old saying? Life is what happens while you're making other plans? :huh:
 
ericscher said:
Sparky -

I'm looking forward to doing a little, er... performance enhancing.

Add a 22' ESP center tube some extra bracing and a wave shield; then replace my 50hp Yamaha with 20" shaft 225 horse Yamaha on a hydraulic jackplate... Yup. Oughtta shorten that lake right up. :D
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eric, You might hit ludicrous speed with that set up.
 
sparkdr220 said:
I will check next time out. I didn't think running at a lower rpm would be a bad thing as long as i'm hitting 18-19 mph.
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I did check the prop, however I had to do it from my Seadoo in the water. The only numbers I could see from my angle were Y2 589. Tried to google and found nothing.
 
sparkdr220 said:
I did check the prop, however I had to do it from my Seadoo in the water. The only numbers I could see from my angle were Y2 589. Tried to google and found nothing.
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I can't tell you sure that what you found was a part number, but it's probably worth asking at the parts counter.
 
ericscher said:
Ace...

Back the boat into the slip and trim the prop up out of the water. You should find the markings you're looking for on the rim of the hub.
Click to expand...
I had the prop out of the water and I used my grab stick to spin the prop. I could see the writing but I could not make out what it said from the back of the boat. I am going to get my SeaDoo out next weekend and so I will be able to check.

I have 25" tubes and I had 7 people onboard. I was pulling a tube with 2 people in it, my boat was turning 5500RPM at WOT. Don't know what speed I was going but would have liked to have a few more MPH. However, it was a big 3 person tube and my boat was well loaded. I am guessing I am setup properly! Next week I will check the prop and will have my GPS onboard so I can measure speed. We had too much going on this weekend for me to look more into this.
 
I have a 22' bennington with a 50 hp Yamaha with a 13p prop and I get 5500 rpm and 19 to 20 mph on a gps, but that is with clean tubes. If you moor you boat at a dock it will have growth that takes a few hundred rpms off and a couple of miles per hour.
 
Ok, I finally got my GPS out and I was really disappointed with the results. I had wide open throttle and the engine was maxed out at 5600 RPM. My GPS indicated 14 MPH. It was actually flopping between 13 & 14 MPH. The boat had two people on board and the waters were moderately calm with little wind. I had the top up. Again, it is a 20SLI with 25" logs and a Yamaha 50HP high thrust engine. I have attached a picture that shows the stamped information on the prop. I suspect I don't have the right prop on it, but it came that way from the dealer. It would be nice to get 18 or more MPH!

dscn1283 (Prop ID).jpg I believe it says: 48 854340A33 9PL

I think I found the part number. I think the above part number is a Mercury Black Max Silver 14x9 prop. Any suggestions of what I should use?
 
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