9.8 Enough HP?

drivadesl

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Apr 13, 2011
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I'm looking to add OB power to my 14' Starcraft aluminum boat. I don't have weight specs for it, but it is a vee hull, all welded open style with pedastal seats rated for 40 hp and 5 persons. Right now I have it set up with just a bow mounted trolling motor but looking to add an outboard for use in lakes that allow them. So I'm wondering whether a 4 stroke 9.8 HP would be enough to get it on plane with say 3 adults and gear.

I am looking at used engines, and found a 4 stroke Johnson 9.8 high thrust tiller model for sale with electric start which I prefer so I could also keep a battery charged for the trolling motor. Will this be enough or should I go larger? I like the idea of the 9.8 since it is the limit for many of the smaller lakes. I can always get another larger engine (25-30hp) if I want something for bigger water.

Appreciate any insight from those who have been there. Thanks.
 

tmcalavy

Rear Admiral
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Aug 29, 2001
Messages
4,005
Re: 9.8 Enough HP?

Uh, no...if you intend to take anyone else with you. Rule of thumb is 75% of the boat's rated hp for base-line, acceptable performance. With three adults, the 9.8 probably won't plane your rig.
 

ezmobee

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Mar 26, 2007
Messages
23,767
Re: 9.8 Enough HP?

No it won't plane it. It will push you along just fine though. Heck we cover a lot of distance in my dad's little 14' with 3 adults with only a 4HP.
 

drivadesl

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Re: 9.8 Enough HP?

Fair enough. I know the 3/4 rule, but when reading some posts on similar 2 stroke engines, seems some guys are putting these on 14' boats similar to mine and are satisfied. With the HP limit rating on some lakes, not much choice so figure I can putt along leasurely and not be in a rush. Certainly would get better performance with a 30hp motor, but then more limited where I can take it. Thanks.
 

steelespike

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Apr 26, 2002
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19,069
Re: 9.8 Enough HP?

If the boat is a bare bones you might be able to setup to plane with 3 but it will likely be a struggle.If your 200 pounders forget it.As far as charging the trolling battery it might help a little but hardly enough to notice.
It would likely take 2 to 4 hours run time for every one hour of use.Depending on the charge rate. A 2 stroke would be lighter, plane a little easier and be simpler to maintain.
 

Navigator_Victory

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Apr 3, 2011
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284
Re: 9.8 Enough HP?

I think plenty for small lakes....I have gone many miles up creeks and along shore lines with three high school friends would not move as fast today as we did back them...140 then 190 now.......but, I did always want a bigger motor but, that ws just so I could go faster....not sure you are going to get it on plane though.....maybe see if you can find someone to borrow from and try it out..? or better yet make that part of the prerequsite of the purchase
 

RRitt

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Mar 30, 2006
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3,319
Re: 9.8 Enough HP?

how much does your boat weigh?
I have a 14' vee skiff that was rated 40HP but previous owner beefed up transom and hung a 60HP. I let my teenager have carte blanche with the skiff so I don't want it to go fast. However, it's the only boat I got that can do 4" of water and bounce off oysters. So it needs to go fast enough to keep me happy but slow enough to keep her out of trouble. 10 HP was not it. With just me, fishing gear, tank of gas, and cooler full of ice the boat is about 600lbs. 10 horse worked too hard and plowed too much. It would catch plane sometimes if the wind was at my back - but mostly it just plowed. I think 18 would be the perfect amount. without the teenager i would be going 25HP. If I was still a young buck who didn't mind getting bounced around then 30-40. I know the old fisherman had 60HP but I think he was dragging nets. a 14' boat going fast just isn't all that safe.
 

drivadesl

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Apr 13, 2011
Messages
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Re: 9.8 Enough HP?

Thanks for the replies. I figure that it will push the boat along enough to get where I'm going at a minimum fully loaded so thats fine. That still gives me lake access. If it planes say with just me and my 12yo son that would be a bonus, and if not no biggie. I was thinking 4stroke since I'm not a fan of the smoke you can get sitting right at the motor on the stern. Plus figure eventually they will ban 2 strokes on some of the smaller lakes, and in particular the reservoirs.

The one I'm going to look at is a Johnson high thrust with a high output alternator so was hoping it would help keep the trolling motor charged. I know there is some more maintenance with the 4 strokes, but I just never had luck with 2 stroke reliability. Please lets not go into a debate on it, I'm saying that I want to try out the 4 stroke for myself and see how I like it. I can always sell it if not happy with it. I'll let you know if I can get this one. But if not maybe will look at one of the tohatsu's.

Thanks for the input again I really appreciate it.
 

ezmobee

Supreme Mariner
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Mar 26, 2007
Messages
23,767
Re: 9.8 Enough HP?

A "high thrust" is for a large boat kicker or a pontoon. That model would definitely kill any chances you might have had at planing.
 

drivadesl

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Apr 13, 2011
Messages
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Re: 9.8 Enough HP?

Wasn't aware of that, thanks for the heads up. Keep on looking I guess.....
 

RRitt

Captain
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Mar 30, 2006
Messages
3,319
Re: 9.8 Enough HP?

i'd look for a 15 tohatsu. if 15 is enough then great. if it's not enough then change the carberator and turn it into a 20HP.
 

drivadesl

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Joined
Apr 13, 2011
Messages
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Re: 9.8 Enough HP?

I'd prefer if the 10hp would convert to the 15 like a jonnyrude can...Any way to supe up a 10hp 4 stroke?
 
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