Usage:
3508 ( 96Y ),
3512 ( 50Y ),
3516 ( 29Z ) Marine Engines
- SUPPLEMENT: 05/01/89
SERVICE MAGAZINE; APRIL 17, 1989; PAGE 15; "Orifice Plates Can Reduce Foaming In Expansion Tank" in 3508 (69Y), 3512 (50Y), 3516 (29Z) Marine Engines. Illustration 2 does not show the size of the orifice hole in the center of the plate. Add following sizes to the orifice hole:
3508 Marine: 44.4 mm (1.75")
3512, 3516 Marine: 38.0 mm (1.50").
--------------- END SUPPLEMENT ---------------
If foaming in the expansion tank and loss of coolant is reported on the above marine engines, two orifice plates can be installed to prevent this from occurring. Install a plate between each flange and the temperature regulator housing cover as shown in Illustration 1. The orifice in the plates will reduce the volume of coolant flow into the expansion tank and help to prevent foaming.
The orifice plates can be made from mild steel plate, 1.60 mm (.062") thick. See Illustration 2. Note that the orifice size is smaller for the 3512 and 3516 Marine Engines. Four, new 2N0931 Gaskets are needed; one on each side of each plate.
Illustration 1. Location of the two orifice plates that can be installed.
Illustration 2. Dimensions for making the orifice plates.