AQ151 might probaly work with the boat , performance will be similar to AQ170, AQ151 has higher rpm and maybe slightly lower torque and possibly some hp more. AQ170 is stated 170hk SAE and AQ151 is 150 hp DIN. Higher rpm which might also produce more noise. We have one DC21 (same hull as 21 weekender) with AQ151 newly installed top speed is around 28 knots.
I would however recommend to install a V6 or V8 engine We have one 21 Weekender in the Fjord club with a newly installed Volvo Penta V6 4,3GXI top speed above 35 knots.
