fittings work well with hard tubing, PVC, PEX, copper, etc. Don't try them with "soft tubing" i.e: hose. There is a hose barb adapter that will transition from SeaTech fittings to hose. (See part #'s 28253 & 28254 on pages 370 & 371 in the above linked catalog.)
If your leak is at the connector at the suction side of the water pump, replace the connector (part 21025 & 21026 on pg 388).
If the leak is at the connector on the pressure side of the water pump, SeaTech has water pump connectors (pg 370 of above linked catalog). Connection can then be made to the "hard tubing" using other fittings as needed.
One thing to keep in mind, most of the problems that occur when using SeaTech fittings are due to:
1- Using them with non-compatable tubing or trying to use them with hose without the required transition/adapter, or
2- Not fully inserting the tubing into the SeaTech fitting. There is a scribe line on the fitting showing the depth of full insertion.