volvo 270 heavy steering only at speed

hello all,hope someone can help,i have a fjord 21 inboard cabin cruiser with a volvo 270 drive,have mated it with a peugeot turbo diesel 120 hp,steering is light when below 1200 rpm (5mph) but goes heavy when the power is on above 1400 rpm (7mph) and stays heavy all the way up to 4000 rpm(35mph)
have renued all bearings/pivots, greesed everything,no play in anything,everything is "as new" .
steering is very light at idle,little finger operation,no power steeing fitted.
point is it this normal, can i do anything about it,am i missing something,is it a torque thing going on from the engine ? prop is a 14 x 19, is it a load thing ?

need help before i do something silly like fitting a couter reacting plate onto the front of the drive to "equil" the surface area up infront of the pivot point to get free power steeing.

dont want to fit power steering,a complication i dont need,and it never had before.

any help gladley recieved.

Re: volvo 270 heavy steering only at speed

The exhaust port/trim fin (Item #4 in picture below) trims the drive at higher speed, if it's turned the wrong way or missing or loose, the steering will pull very hard in one direction.
Adjustment will be necessary.