I have finally had it with the Grocco in tank pump system that came with this Grady. (2001 Marlin300). I removed the Grocco pump from the top mounting plate and re-installed the plate to the top of the tank. There was an extra 1 1/2 " threaded plug in the top of the tank. I removed that and installed an 1 &1/2 " Male thread 90 degree hose adapter. On the inside of this fitting I fit and epoxied (JB Weld) a 10" long, inch and a 1/4 PVC pipe to reach about 3/8" off the bottom of the tank. I mounded a Jabsco Macerator pump just forward of the tank and in the port side compartment. ( all under the aft berth)... I wound up mounting the pump horizontally and from starboard to port, on a 12" piece of 2x6 lumber secured with 2 brackets to the 2x4 that makes up the tank compartment. A picture is worth 1000 words, I will work on that.
Used the following ... 2' of inch and half sanitation hose.. 1& 1/2 '' male 90 degree hose adapter ( for tank) ... 1&1/2'' female 90 degree hose adapter( for input side of pump.).... 3/4' by 1" "I" hose connect fitting (connects the 1'' pump output to the 3/4'' Grady discharge hose.) ... 2'' of 1'' id hose to connect the 1'' side of the adapter to the 1" pump output.... SS clamps..
Used the following ... 2' of inch and half sanitation hose.. 1& 1/2 '' male 90 degree hose adapter ( for tank) ... 1&1/2'' female 90 degree hose adapter( for input side of pump.).... 3/4' by 1" "I" hose connect fitting (connects the 1'' pump output to the 3/4'' Grady discharge hose.) ... 2'' of 1'' id hose to connect the 1'' side of the adapter to the 1" pump output.... SS clamps..