New build, Transom height and max outboard HP input request

Hello all. My first post anywhere online. I’m building a 22 x 7.5 Foot river cruiser, ply on frame, epoxy/fiberglass construction. Hull speed 6.5 mph. The design is called “Haven” from Australia circa 1970. It should look like this when done.
It looks like this now, about 70% complete.
The design weight for the completed hull is 2200# with the waterline at 12”. I think when fitted out it will come in at 4500-5000# (two people and stores for 2 weeks). Its a trailerable design. I’m building to cruise rivers and canals here and in Canada. 1-1/2 years into build. Hopefully 1/2 to go.
I have two questions (well several hundred but…) that are holding me up right now.

1- The original design called for a 15” transom. Family is encouraging me to change that to 25” as I can accommodate that in the design. I think that would limit me in outboard choices and am leaning to 20” for a Evinrude E-Tech. What would you recommend for height?

2-The design allows for up to a 100 hp outboard with the 15” transom and 100hp is what everyone is pushing me to get. However as this is a displacement boat I thought the Evinrude E-TEC 60hp pontoon motor with its lower gearing would be more than enough. 90% of the cruising will be no wake and in an emergency (bad weather, health) it would still get into the low teens. With all the time and effort I’m putting into the build, I plan to buy the motor new this fall when I see a good offer. However I don’t want to buy more than I need. Your thoughts on motor size and type.
Thats it for now. Any feedback would be appreciated.
Jim

 

I would agree that 15" IS TO LOW. In the old days all outboards had 15" legs. Now you have options and all brands offer 20" for most all of their models. 25" is popular and many models do offer this option. I WOULD GO WITH A 20" it is less expensive than the 25" and you can you can always raise the engine mount to 25" if the need arises. 20"
is the most popular height now.

 

The E-tec 65 Pontoon comes in 25" length
http://www.evinrude.com/Content/Pdf/en-US/2015_Evinrude_Catalog.pdf#zoom=100

 

20" is OK, 25" is better, 15".....no way. You may not even be able to find anything in that HP range in 15"

 

The only hitch might be a 25" would have less re-sale in the 60hp range, where few boats have the transom cut that high. But 100hp it would be OK, imo.