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20sl how much power

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Davey25

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Has anyone pulled a water skier or wake boarder behind the 20SL...just in the process of ordering but my wife... 120 lbs would like to be able to ski or wakeboard behind..nothing crazy shell be happy if she can get up...would the 23" pontoons be better? And do you think much difference between the 50 60 70 hp motors. Thanks
 
I don't know about the 20sl at all, but my next door neighbor had a much bigger and heavier 25' Benny RL 2 toon with a Mercury 75 4-stroke. Their 20 something sons, all good size young men, used to wakeboard and combo ski behind it all the time. Not a great pull, but with that motor at least do-able.
 
I have the 20' SLX with a Yamaha 70 Does anything you need it to do

Great power tubing skiing etc . Yamaha 70 hp rocks and very quiet
 
I would definitely have the 25" toons, just for the extra buoyancy, should help you get the most out of the motor, IMHO.
 
By all means, go the 25" toons, and the largest engine the boat is rated for--70 hp.

Most of the difference between the 50-60-70 hp engines are ECM programming. They weigh the same.
 
Davey,

My experience with that setup (20ft+70hp) that it will top out around 23 mph, that's a little slow for slalom skiing. Your wife and small children could slalom ski, but an adult male 160 lbs + would have problems! There is a sweet spot when your slalom skiing and it's around 28 to 30 mph. Also you need the HP to pull a slalom skier out of the water quick. If your only pulling tubes/skiers on 2 ski's it will do that.

RiverBill
 
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My 20SL, 25" tunes with a 50 HP Yamaha will only do about 18-19 mph and can pull little kids in a tube fine enough for their excitement. I would put the 70HP on if you want the best skiing/tubing you can do with that boat. I bought mine at my max budget at the time and will probably upsize the engine in the future. I pulled skiers for 18 years behind my old boat and agree that for 75% of skiers I pulled (adult and kids), 23 mph is fine. For slalom, I liked 28 mph...
 
I also know that my 2075 GLi with a 90hp yamaha, only went 22-24mph, now I suppose depending on how you prop it, but your gonna want the holeshot, so you have to lose some top end.
 
BulldogsCadillac said:
I also know that my 2075 GLi with a 90hp yamaha, only went 22-24mph, now I suppose depending on how you prop it, but your gonna want the holeshot, so you have to lose some top end.
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I concur with Bulldog. 20' with 25" tubes, and a 90hp Yamaha will do aprox 25mph gps depending on your altitude. That is with a 13" prop, the 15" does not work well, as far as rpm and load. Marginal at that.
 
I have a 2012 22sslx with the 32'' elips and lifting strakes and a 90hp yamaha. With me and the wife and 1 kid I got 30.3 mph on the gps and pulling a skier or tube is not a prob. Awesome ride and it turns tight enough for me.
 
I have been told the with the 25 inch pontoons ,every 10 additional horse equates to one additional mph .

These are the estimates I have been told

50 = 18-19

60 = 19-20

70 = 20-21

This not from me, just a dealer I visited in the order process
 
I have a 2012 20sl with a merc 60 bigfoot . I top out at 20mph per gps with a quicksilver nemesis 4 blade prop. and wow what a diff. the 4 blade made the thing jumps when u give it gas now and it will do the same mph nomatter if i have 2 pep. 0r 10 pep. on the boat. I could only hit about 18 with my stock 3 blade prop and was only getting about 5200-5300 rpm at wot and now i get 6000 rpm all day long. All I can say is we love our 20sl.
 
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you might want to consider that other passengers and gear (coolers etc) will further decrease the speed. I think a 90 is a minimum hp . JMHO
 
1trotter said:
you might want to consider that other passengers and gear (coolers etc) will further decrease the speed. I think a 90 is a minimum hp . JMHO
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I have a 20sl with a 70 yam 4stroke. Plods along at 17 or 18, with a quarter tank, and me and mom, nothing else. 14x13 prop, 6000rpm. Prop God says 13.5x12, but I wonder if anybody has similar config, before I go the prop route
 
Rondo64 said:
I have a 20sl with a 70 yam 4stroke. Plods along at 17 or 18, with a quarter tank, and me and mom, nothing else. 14x13 prop, 6000rpm. Prop God says 13.5x12, but I wonder if anybody has similar config, before I go the prop route
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Can't offer any help on what prop to use, but I'm surprised Ken recommends going down in both diameter and pitch given that you already can achieve you max RPM (6000). If anything you should add a little more pitch for more speed, or more diameter for holeshot and efficiency.

Unless you are going from a 3-blade to 4 blade or aluminum to SS?

Also if those numbers are correct you calculated slip is a piss poor 43%. Something is seriously off and/or wrong. Are your toons clean? Any water in the toons? Is the prop hub spun? What shape is your prop in?
 
Thanks for the response. Yeah, slipping like heck. I can go from 5300 to 6000 rpm with no increase in velocity. Feels like I'm still tied to the dock. After my initial assessment of the 6000rpm (+ a bit more on a calm day) I had my prop guy put a bit of cup on the prop. A bit. But, dropped rpm by 1000. Oops. But, speed is the same.

I suspect prop God is thinking slipping is bad as you said, because of hull resistance, and going down a bit would give more oomph to overcome resistance. Toons have no water. It did live its previous life in the water. Toons were ugly. I cleaned them well where I could clean them well. I am thinking there might be crud on the inside surfaces down low hidden by the trailer bunks.

I am not going to do anything else prop wise until I am certain the Toons are spotless. But, there is bottom paint, albeit in good shape. Once that variable is controlled I will address the prop.

Sounds like the engine is straining and never gets into its power band. That's a weird statement I know, but you know how an outboard is supposed to sound.

By the way, hub is not spun. And, compression is great on the Yamaha

Thanks a ton for your support
 
That lack of increase in speed at the upper RPM end is curious. Maybe the water is getting aerated by some turbulence at those higher speeds so your prop is just ventilating? It doesn't take much to get a prop to slip.

I know you're not wanting to throw a bunch of money at this but a relatively inexpensive aluminum prop can eliminate a lot of variables. The engine doesn't seem to be the cause (you can generate the necessary RPM) and if the prop is brand new it can only be either the hull or something with the setup of the engine (mounting height etc).

Pictures of the hull and engine might help generate ideas from the community.
 
That's the plan. Once I am sure the toon are spotless I'll go prop. Prop God sells me one and if it isn't right I send it back, only losing $40. No brainer.

As for ventilating, that's a concern I have. Not overtly venting where the rpm goes nuts, but venting in the sense that the prop sits in turbulent water. Boat has that center pod where engine is mounted and it looks gnarly back there. Engine is on lowest hole and I thought of lifting, but the wash would be worse up high. If I could bet the engine back further with a jackplate like my big boat, that would be interesting.
 
Bennington has stated on the forum in the past, a jackplate will void your warranty.
 
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