I agree with Charlie that is a big boat to move.I have a 9.9 4 stroke merc.long shaft on my 19 foot Lund and it Is just the right amount of power in all conditions.You want to make sure that the kicker will get you home if any thing happens to your main motor.I know it's for trolling but it's also a back up power sorce.Yamaha make high thrust motors with charging capability.You might want to look at these also.Good luck.

Erin

My advice, and I have been running kickers since 1988.
Get a 15HP for that size boat, and get one with a charging circuit, downriggers, fishfinders, VHF and stereo all draw power and nothing sucks worse than a dead battery out in the broads when the wind is kicking up. I always plumb my kicker to the main tank and use a second oil injection system, that eliminates the need for a separate fuel tank. Lastly, there is nothing wrong with buying used. I presently have a 15HP Johnson kicker I pd $800 for used 14 years ago. It gets significant use every year both on my fishing boat and as the primary unit on my duck boat, and thus far I have only replaced spark plugs once and impeller twice. That beats the cost of a new motor by qite a bit.
my .02
Throbbin Rods who is relocating to Ossipee/Wolfeboro starting Monday

I love my honda 15 hp
it is an electric start tiller model
it has 1 cord to hook to battery for charging and starting
You don't even need electric start with honda's they come with a charging system and a cord anyways, no extra.
Honda's are also the only small outboard with a voltage regulator, this is good if you are going to hook in a troll-master you don't have to worry about cable routing messing up the currents.
i have had no problems with it and it pushes my 24ft. grady white at 5-6 mph wide open
it is not a power thrust or anything special it is just a regular honda 15 with a 4 blade prop.
a 9.9 would probably be fine but i don't really know for sure i have always used 15hp kickers.
If you are putting it on a bracket be sure to get the Garelick eez-in model for 4 strokes with the 15" lifting range and not the one with only 9 inches.
good luck.

I just talked to Bill at Shep Brown's, he has a 15hp Honda in stock no electric start though. I am just waiting for a price. Thanks for your help.

you will need a 20in. long shaft, not a 15in.

the electric start shouldn't matter on the honda because of the charging cable. other brands w/o electric can't charge. That is if you don't mind pull starting.

Make sure with the dealer on the charging cable i am 99.9%sure about that.

On my 2000, 18.5 Lund Tyee; I have a 1998 Mercury kicker, 15 hp, 4 stroke, electric start and tilt with a voltage regulator. With the kicker at WOT, it will push the boat at 9 mph on a clam day. On the size boat that you have, I wouldn’t go any less than a 15 hp, the 15 is only 7.5% of your 250 hp main motor.

I have a 15 h.p Yamaha,4 stroke,electric start,tiller,20 inch shaft,which has been sitting in my cellar for the last 5 years. Motor has less than 25 hours of use it's just like new. I sold my 16 ft.Lund and bought an 18ft. so it's been collecting dust ever since, worth a look. If interested email me.

Just got done dueing this last year. i have an 8 hp merc 4 stroke with elc. start. Push's my 18' cuddy @ 8mph wfo. Plenty for lakes, i also agree with Adrian on the garlock transom mount.buy the black 4 stroke version. Comes with easy formula for mounting instructions,(just sucks drilling holes in the transome, ouch)next you will definately want a controll king our such to controll your speed from the dash...Priceless @ $200.... and an easy install.And an easy steer which conects the two motors together so you steer with the wheel.
Any questions Lemeknow!
Whip