This fitting relocates the return line for the heater to the inlet side of the raw water pump, increasing water flow thru the heater core at idle speeds. The 1-1/4" barb is for PCM GM, Indmar Ford & GM, and GM Mercruiser engines.
Increase your heat while idling!
1 1/4" Main to 5/8" barb for heater hose
OEM installed on all Malibu Boats with heater option 05+