Hey all new to the site and appreciate any advice you can give me on this question. Im looking to buy a jon boat and am going to go look at a 2016 Alumacraft MV 1648 NCS tomorrow. I have a 1987 15hp Johnson 2 stroke short shaft that I want to use on it, will this motor be sufficient for this boat? Specs say it has a 20" transom which mean a long shaft would be ideal & Ill probably eventually get one but can I enjoy it for a year or two with the short shaft?
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Will a short shaft work for Alumacraft 1648 NCS
- Thread starter bernieds
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maintenanceguy
Well-known member
short shaft and long shaft mean different things to different people.
Get the shaft length that matches your transom. I have a kicker/backup motor on my boat that has a shaft that's 3" shorter than ideal. It works as a backup but would be awful as a primary motor. Occasionally I use it just to make sure it gets some exercise. If the water is choppy or I go over a wake, the prop gets close enough to the surface that it sucks in air. As I go up and down the motor speeds up and slows down as the prop depth changes.
Get the shaft length that matches your transom. I have a kicker/backup motor on my boat that has a shaft that's 3" shorter than ideal. It works as a backup but would be awful as a primary motor. Occasionally I use it just to make sure it gets some exercise. If the water is choppy or I go over a wake, the prop gets close enough to the surface that it sucks in air. As I go up and down the motor speeds up and slows down as the prop depth changes.
CedarRiverScooter
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Take a tape measure. Compare to your motor's height from transom clamps to cav plate. Cavitation plate needs to be lower than bottom of boat a little. Note that motor leg will not be exactly parallel to transom.
zekepa
Active member
I have a short shaft Mercury 20 hp on a Tracker with a 20 in transom. To get it to work I had to put a jackplate on it. The combination of set back and lowering the motor a couple inches works bow. Before I installed the jackplate as soon as it got on plane it would start sucking air.
wmk0002
Well-known member
A homemade jackplate with about 5" of setback that you can adjust down some would probably work.
You can also convert those old 9.9/15hps between long and short shaft pretty easy. If memory serves me right, the drive shaft slides out of the lower unit and the shift rod unscrews meaning you can remove those parts and replace with the correct longshaft ones. Then you have the 5" spacer on the leg housing and also need an extension for the water tube.
I'd venture to say that you may be better off to try to trade your motor for an identical one but with a longshaft. There are lot of people in your same situation who would at least entertain the idea.
Lastly, those Alumacraft 1648 NCS models are great boats, especially for someone who likes the open concept and likes the ability to mod them how they like. I definitely wouldn't let the transom size dictate buying it or not if it's a really good deal.
You can also convert those old 9.9/15hps between long and short shaft pretty easy. If memory serves me right, the drive shaft slides out of the lower unit and the shift rod unscrews meaning you can remove those parts and replace with the correct longshaft ones. Then you have the 5" spacer on the leg housing and also need an extension for the water tube.
I'd venture to say that you may be better off to try to trade your motor for an identical one but with a longshaft. There are lot of people in your same situation who would at least entertain the idea.
Lastly, those Alumacraft 1648 NCS models are great boats, especially for someone who likes the open concept and likes the ability to mod them how they like. I definitely wouldn't let the transom size dictate buying it or not if it's a really good deal.
wmk0002,
Thanks a lot for the advice. I've been looking for a boat like this 1648 NCS for awhile not realizing my motor may not work but am really excited about it and think I'll buy it either way. Two quick questions 1st how fast does your 9.9hp move your 2016 NCS? If i get this boat most of the time it will just be me (6'1" 250lbs) but once in while it'll be me my shorthair (70lbs) and the little lady (110lbs) and I'm hoping I can still get 15-18mph with the three of us & 2nd how is the stability on the front casting deck fishing? Thanks for any info.
Thanks a lot for the advice. I've been looking for a boat like this 1648 NCS for awhile not realizing my motor may not work but am really excited about it and think I'll buy it either way. Two quick questions 1st how fast does your 9.9hp move your 2016 NCS? If i get this boat most of the time it will just be me (6'1" 250lbs) but once in while it'll be me my shorthair (70lbs) and the little lady (110lbs) and I'm hoping I can still get 15-18mph with the three of us & 2nd how is the stability on the front casting deck fishing? Thanks for any info.
wmk0002
Well-known member
bernieds said:
My 1992 9.9 Johnson was actually converted to a 15hp. With me (170 lbs), trolling motor, group 29 battery, 3 gal fuel, fishing gear about a 50lb floor and a few other odds and ends it would go about 20mph with the factory 10" prop. Add in my dad, who is similar size to me, and it would drop to around 18mph with the same prop. Speed was good but the rpms were a little low so I reverted back to the 8" pitch that came on it when I got the motor. That prop would keep it around 6700-6800 rpms (7000 is upper range of WOT for this model) with both of us in there and still run 18-19 mph but with much better holeshot. I've since moved that motor to an old 1440 flatbottom since I got a new 25hp Yamaha on my 1648 and swapped the prop to a 9" pitch 4 blade.
I also had an early 80's 9.9 I ran on the boat as well and with the factory 10" prop it ran about 16-17 with me solo and about 15 with an extra person.
Lastly, the front deck is really stable on mine but keep in mind that it is a flatbottom which I'd imagine is a bit more stable than a mod-v front. The only issue I have with the front deck is the length - at only 4' long it's a little cramped. For some time I have been looking to add a removable deck extension to mine to extend it to either 7 or 8' to allow more room for me plus give the option for two people up front and to try my hand at bowfishing. On the flip side, the short deck is nice at times like when anchoring in current and fishing out the back of the boat.
