Whats the minium hp outboard engine I need?

mjmarotta

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I have a 17.5 ft. 950 dry weight bass boat. What is the smallest engine I can put on it and get it on plane? will a 48hp do it don't care about going fast. 25mph 30 mph would be fine. Thanks
 

bonz_d

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48 might work if propped correctly. Big blades, small pitch.
 

southkogs

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I'm thinking she'll fight to get on top of the water, and if it did get on plane it might get real "mushy" if you try turning it too hard.

The standing rule is 75% of max for minimum which would put you around a 90HP. If you already own the 48, I'd give it a try. Nothing to lose there. But if you gotta' go get something, I'd look for a 70HP or so.

I had a 15' that was rated for 100HP. I ran a 50HP on it for a while and it would get up on plane with just me and a kid aboard, but add a second kid and it wouldn't do it. Boat was a little heavier than yours, but not too much - I think about 1,200 or so.
 

Alumarine

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You'd also be running it at near full throttle if not full.
You'd be surprised how much fuel a small motor can drink at WOT.
 

bonz_d

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The boat pictured in my signature is max rated @ 75hp. It's dry weight is listed at about 650lbs. I am running a Johnson 60hp 2 cylinder on it which is basically the maxed out version of the 50/55hp model. So that's 80% of max hp and it performs very well. Now I also get to see many of these same boats powered by only a 40hp OMC so that's a hair above 50%. How does it perform? Couldn't tell ya because I have never actually been in one powered that way.

Does it work? I would guess yes otherwise there wouldn't be so many of them around. Would it be enjoyable? Doubt it.
 

Silvertip

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To go 25 - 30 mph you have to be on-plane. How efficient the hull is will determine what HP it takes to get on plane. Since the boat is rated for a 125 and the 70 - 75% rule definitely applies, then a 48 is going to be a real dog. I also find it difficult to believe a 17.5 foot boat weighs 950#. Add the engine, yourself, your gear, gas and adult beverages and I think you will be very disappointed.
 

series9

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I've got a 700# McKee (without engine) with a 50hp Evinrude. A 40 would work, but not a 30.

And I completely agree with Marc C. If you run a two-stroke at WOT, it will devour fuel.

More is better. Find a 90.
 

sublauxation

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My 18 ft Aluminum Sylvan weighs more than that so I too am pretty sure you're off on your weight estimate. It's rated for a 135 and I have a 90 on back. It planes well and will do 44 on GPS. How old is the boat? As to the 70% rule, I could be wrong but at some point outboards were rated at the powerhead vs now at the shaft so if your boat is older a 125 will be equivalent to a smaller newer outboard.
 

gm280

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Certainly mixed opinions here and I'll give another as well. 48 HP isn't going to do the job without special circumstances. So I would buy as big engine as you can find for the money, but not to exceed the 125 HP max rating, and then throttle back and cruse in comfort. And then as the engines gets tired, and they all do at some point, you still have enough to still get the job done without issue. And fuel economy will certainly follow the throttle handle as well... Just because you have the capability to go fast, doesn't mean you have too. And resale down the road, will attract more buyers with a bigger engine. JMHO!
 

WIMUSKY

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FWIW, I'm in the 90 camp too......... I personally wouldn't go with anything less....... Start adding people, gear and gas and you'll want all of that 90.....
 
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bonz_d

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I have a 17.5 ft. 950 dry weight bass boat. What is the smallest engine I can put on it and get it on plane? will a 48hp do it don't care about going fast. 25mph 30 mph would be fine. Thanks

Back to the beginning.
There now you have many expressions of opinion and all with valid points. But I will go back and again state that yes that 48hp may do what you want but it would have to have the correct prop and yes it would be woefully underpowered. It could get up to plane with light loads but would also have no reserve power should it be needed.
 

WIMUSKY

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With one exception, a 48hp will never push that boat 25-30mph....... Maybe you'll get 25 with a good tailwind at WOT....... Maybe.... :)
 
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Willyclay

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Having more power available than is normally required is a very desirable objective! Good luck and let us know what you decide.
 

sublauxation

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I should add, the guy I bought my 18ft aluminum boat from used it on Lake MIchigan with a 35 or 45 HP Merc. He trolled for Salmon all day long and it worked perfect for him. I'm guessing he had to keep a close eye on the weather as I'd have hated to be out 10 or 20 miles when a storm came up.
 

bonz_d

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propped with an 11.5 X 9 X 4 might, but I've been wrong before.
 

roffey

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if it were me I would go with the max HP, you don't have to go full throttle but it nice to have when you need it.
 
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