Question for an electronic expert

[Jack46]

Hello. Back in 2016 I have refitted my Boston Whaler Montauk 190 boat replacing a 2011 115HP Fourstroke with a brand new 150HP 2016 Fourstroke.
The mechanic did not replace the cable from the engine motor to the console mantaining "...it is the same...".
Now I have at hand the "new" cable P/N 84 8M0075945 Harn Kit Fuel/PADDLE Wheel. I cannot find the P/N of the installed ne.
The engine works properly but I do not see all the info on the Smartcraft instruments. It happens that when I try to select "Trolling Mode" I receive the message "Paddle unavailable".
My guess is that the cable is the culprit and I should replace it with the new one, but before entering a complex operation (the tube between the console and the motor is very very populated) I'd like to receive an opinion from an expert.
Thank you!

Post scriptum.
Looking carefully at the kit I am thinking that it is something additional and/or partially replacing the existing cable.
This is only a guess, but, before arguing with my mechanic I'd wish to be sure of what I'm stating. Thank you.

[boats.net]

That harness is the Boat Harness, it connects to connector on engine and the fuel tank senders and speed paddle wheel connects to that boat harness, You may already have that harness if fuel gauge is working on Smartcraft gauge. You would still need to purchase a speed paddle(859223A01) if don't already have one mounted on transom of boat.

[Jack46]

Thank you.
Problem arised when I tried to set trolling speed and I have received the message "Paddle unavailable" on the Smartcraft gauge.
I really do not have any need to discover water temperature as I have plenty of transducers.
I only need to set the trolling speed but I cannot figure out what this sensor (speed paddle) has to do with motor revs.
Can you please shed some light?

PS Could it be just a matter of setup?

[boats.net]

If you have Smart Tach and Speedometer then you will have a Troll Control function on Tach and on Speedometer, the tach troll control will adjust RPM's and speedometer troll control will adjust MPH. The speedo will require a speed signal either a paddle wheel or connected to a GPS.