Arduino Driving Pump via MOSFET
Vin is only rated to supply at most 1A due to the reverse polarity protection diode in series from the barrel jack to the Vin pin.  You try and draw 1.7A thru that and you may smoke it. 
The Vin header is also only rated for 1A.

Connect the motor to the supply directly. The Arduino Gnd must also connect to the supply.
R2 limits Arduino IO pin current to a safe level. R1 keeps the MOSFET off while the Arduino boots up. Diode dissipates motor generated current when the MOSFET goes from On to Off. The RFP30N06LE looks to be rated for full turn on with Vgs of 5V, and Rds of 47milliohm, that part should be ok to use.

Powering the Arduino from the same source as the motor may cause issues. If you can power the Arduino from USB or a seperate battery pack and not the same 12V that powers the motor, that will probably yield better results, especially if the 12V droops at all under heavy loads from the motor. That could cause Arduino resets.







simulate this circuit &ndash; Schematic created using CircuitLab