What size motor for 12 ft V-hull Aluminum boat?

bowman316 · #1 March 23rd, 2009, 01:28 PM

I have a 12 ft Simple Aluminum slight V-Hull boat, and want to use this boat to run up river, this river can get quite a current when water is running. So what size engine would have enough power to get up a fast current? I was looking for a 9.9 hp, but I wonder if a 6 would be able to do the job?

the boat is very light, maybe 200 lbs. And the beam is about 3-4 ft wide. closer to 4 ft wide.

Mark_VTfisherman · #2 March 23rd, 2009, 01:35 PM

Not knowing the size of the river and what the current is, I can't say for sure, but most 12' boats do fine with a 6-or-so.

But if your boat is rated for it, I would go with the 9.9. A small aluminum will really scoot with a 9.9, and save you a lot of fishing time

bowman316 · #3 March 23rd, 2009, 01:45 PM

This is the Susquehanna river, at the Head of the Chesapeake bay. It is about a mile wide, But there is a dam upriver, and when they release water, it may be a 5 MPH current, maybe more.

I had a 2 50 lb thrust trolling motor's on there, and had both going and was just staying still in the current.

jasper60103 · #4 March 23rd, 2009, 02:02 PM

Here's a good thread...
http://forums.iboats.com/showthread.php?t=297930

Mark_VTfisherman · #5 March 23rd, 2009, 02:03 PM

9.9, definitely.

For trolling motors you can guess at about 1hp for every 25- 35 "pounds of thrust."

It's actually not that simple, and I think there is a thread somewhere about the math, but that is good enough for easy figuring.

So a 6hp will just barely creep you over the speed of the current. It may not plane your boat well, either, but I have no reason to say that other than a guess. You will likely plane out about 10 to 15-ish mph with the 9.9, nice for getting somewhere and enough to insure a margin of safety.

That is my opinion. Mileage may vary...

CATransplant · #6 March 23rd, 2009, 03:03 PM

Almost all v-hull 12' boats are rated for 10 hp, so I'd get the 9.9. It'll plane you out, and that's the key to going upriver. With the six, not so much. I use my 6hp on the Mississippi, though, up here in Minnesota. I avoid the river when there's a lot of current, since it's a drag running against it.

bowman316 · #7 March 23rd, 2009, 03:13 PM

I saw an ad for a 7.5 HP honda engine. selling for $250 bucks.

I think that would get the job done, But you never hear anything about honda engines, Idk if they are good or not.

coolguy147 · #8 March 23rd, 2009, 03:31 PM

least 9.9 i got a 10hp 2 stroke and with me and buddy about 135 and 110-115between the both fo us and some gear plug gas we plane out pretty good if he sat in the front. my boat was a flat though with a vi hull in front. would suggust leats 9.9

forget the honda its 4 stroke

bowman316 · #9 March 23rd, 2009, 03:35 PM

yea, 4-strokes are way too complicated for that size of engine. And too much weight.

kenmyfam · #10 March 23rd, 2009, 10:59 PM

Go with the max you can. Best for fighting currents and some reserve power. The difference in fuel is hardly noticeable.

5150abf · #11 March 24th, 2009, 07:26 AM

Had a 12' tinny with an old ('64) 9.9 on it and it did really well in my river, currents would get pretty heavy at times and I never had a problem.

With just me in th boat and the eight spread out just right it would really move out.

A 6 will do but a 9.9 would be better.

Mark_VTfisherman · #12 March 24th, 2009, 11:09 AM

Quote:

Originally Posted by bowman316

I saw an ad for a 7.5 HP honda engine. selling for $250 bucks

I don't care for Honda's but that is not the point. Get a 9.9.

bradleeson · #13 March 24th, 2009, 11:11 AM

I used to run a 12ft with a 6 hp, and always wished I had something like a 9.9 on it. If you find a killer deal on a 6 hp though you should be okay.

Bard1 · #14 March 24th, 2009, 11:42 AM

9.9 is the way to go.

reelfishin · #15 March 24th, 2009, 01:14 PM

I have a 12' Duranautic V hull, it runs along ok with a 1978 6 hp Johnson on it but struggles in anything but the very least amount of current with two passengers. I'm close to 300lbs, and add a passenger and some tackle, and were pushing 600lbs, it moves the boat but not very fast. My 9.9 does a lot better but still isn't super fast. I actually do better with my older 9.5 hp Evinrude since its so much lighter and I don't need to carry the 75lb battery.
I have a Honda 10hp, it's an older Honda 100 4 stroke, it runs great but outweighs my Johnson 25 hp. I wouldn't even consider hanging it on my 12' boat. I believe their 7.5 hp motor is based on the same motor?

I'd go with no less than the 9.9 hp. The best thing I did to mine was to put the 15hp carb on my 9.9, that woke the motor up enough so it at least has enough power to get the boat well on plane and moving along at a nice pace.
My Duranautic is rated for 10hp max and 540lbs.

CATransplant · #16 March 24th, 2009, 01:58 PM

Just to add a small note: The 6 hp I use is fine for me, since I'm almost always on small lakes. I use it on the river, but only when I'm by myself.

If you're going to mostly do river fishing, I'd definitely go with the 9.9 or 10 hp. You'll be glad you did.

bowman316 · #17 March 24th, 2009, 02:54 PM

This would be for duck hunting in the winter on islands up in the rocky shallow part of the river.

Somewhere I would never take my glass boat.

Shizzy · #18 March 24th, 2009, 11:25 PM

I have a 6HP in my 14'er. with all my gear and a trolling motor she isnt as fast as Id like..... 10 HP would be much better.

with just me and no trolling motor or gear she zipps around plenty fine.

sasmit8 · #19 June 12th, 2009, 08:31 AM

Hello
What is the motor rating for the boat?
I have an old 12ft sears V hull--It is only rated for a 7 1/2 HP
I have a Suzuki 6 HP on it.It is all the motor I want on it. Once in a while I use it up in maine on a river with a strong tidal flow.It seems to handle the
currant OK.

Tacklewasher · #20 June 12th, 2009, 12:06 PM

Quote:

Originally Posted by bowman316

yea, 4-strokes are way too complicated for that size of engine. And too much weight.

I replaced a Johnson 9.9 with a Honda BF100 (10hp, 4 stroke).

Weighs 75 pounds. Heavier than the 9.9 but still light enough that it was easy to use and I much preferred it over the 2 stroke, especially for trolling.

I could plane out my 12 foot (rated for 10hp) and hit 26kmh (gps).

The old blue and white Honda's are great motors, require little added maintenance and are not that much heavier. If you are choosing between a 6hp and the Honda 7.5, I'd go with the Honda.

But I do think you need a 9.9. Take a look at the old Honda's before deciding.

coolguy147 · #21 June 12th, 2009, 12:22 PM

my 12foot is rated to 15hp. kinda of a wide boat i guess.

ur expect around 20mph with 9.9 or 10 and with a 15hp( if rated for) expect 30+ maybe.

with a ncie current i would suggest a least 10hp

but we have to know what the boat is rated for maybe some pictures?

MrGadget77 · #22 July 7th, 2009, 03:02 PM

I bolted a 1976 20hp mercury on my 12 ft aluminum boat, and I find it gives me just the right performance...the boat did give up its own name....
ITZA HANDFULL

dbear1959 · #23 July 7th, 2009, 03:38 PM

I had just about the same boat. 12 footer, 3-4 feet wide, and not real deep. I had a 6hp Merc on it and it would not plane unless I sat in the center seat and extended the tiller. Then it was fine, but not real convenient. Go with a 9.9 it should do the job.

By the way I weigh about 200lbs if that helps explain/judge the planing & moving up to the center seat issue.