MSB20210917
4.5”/112# Thrust Lower Units
Brush End Sealing
Click here to download Service Bulletin MSB20210917
Service Bulletin
4.5” (112# Thrust) Lower Unit Brush End Sealing
- Model Numbers: All motors with 112 Pound Thrust Lower Units, EO 1 Horse
- Serial Number Range: : N345MK00345 - Present
- Reason: Explain Historic/Current Variations of 4.5” Diameter Brush Ends/Center Sections
- Actions: No Inventory or Product Updates required, Informational Only
- Related Part Numbers:
- Center Section Assemblies: 2777242, 2777241, 2777250, 2777249, 2777248, 92-200-240, 2777345, 2777346, 2777347, 2777348, 2777343, 2777344, 92-200-340, 2777356, 2777353, 2777354, 2777357, 2777251, 2777252, 2777255, 2777258, 2777259, 92-200-351, 92-200-250
- Brush Ends: 92-300-150, 92-300-151, 92-300-155, 92-300-156, 92-300-175, 92-300-176
- Seal Kit: 2881450
- O-Rings: 701-107, 701-103, 701-098
- Additional References: Repair Manual Chapter Lower Unit Repair; 2004985 Seal Kit Instruction Sheet
Explanation:
The seam between the Brush End and Center Section on 4.5” diameter Motor Lower Units has had some feature changes since release in late 2013.
- (December 2013-June 2015) To prevent the potential for RF interference from errant timing a “Key” is stamped into the Center Section that locks into a notch in the Brush End; this Key system prevents timing changes/rotation of the brushes with respect to the magnets. To accommodate the Key system the O-ring used to seal the Brush End to the Center Section (701-107, 107MM x 1.78MM) was positioned in a thin groove machined into the face of the Brush End.
- (June 2015-July 2019) The groove on the sealing surface of the Brush End that retains the O-ring was made wider and deeper, a Thicker O-ring was used. This was done to make assembly easier; the thicker O-ring (701-103, 103MM x 3.00MM) is less likely to fall out of the deeper groove in the Brush End during assembly. This change made Brush Ends 92-300-150 and 92-300-151 obsolete since 92-300-155 and 92-300-156 are backward compatible as long as the correct O-ring is used.
- (December 2017-July 2019) Elimination of the alignment key. Impacts that shift the Brush End in spite of the Key stretch the through bolts and cause leaking of the lower unit; this became a bigger issue than the potential RF interference.
- (July 2019) With the alignment key gone it was no longer necessary to locate the O-ring in a machined groove. The O-ring sealing method used on most other lower unit O-ring seals could be applied to the 4.5” Diameter Brush Ends. This method wedges the O-ring (701-098, 98MM X 2MM, same as plain end O-ring) on three sides; the face and vertical of the Brush End, and a 45 degree chamfer at the center section. Using the same O-ring on both ends of the Motor Lower unit and an installation method common to most Minn Kota products is a process improvement.
To insure correct parts are available on repairs:
- 2881450 Seal and O-ring Kit includes one of each of the three O-rings that might be the correct O-ring; two Brush End O-rings will be discarded, Armature Seals and Thru Bolt Orings and Plain End/Sonar End O-ring are not affected by these changes.
- Center Sections with a flat surface toward the brush end sub to a kit that includes a chamfered Center Section and a current Brush End
- There is a commitment to keeping these 92-300-155 and 92-300-156 available to avoid unnecessary replacement of Motor Lower Units/Center Sections.
- 701-107 is not available individually, 701-107 subs to seal kit 2881450. Since 92- 300-150 and 92-300-151 sub to 92-300-155 or 92-300-156, making this change to Oring 701-107 is the most effective way to insure no one attempts to install 92-300-155 or 92-300-156 without O-ring 701-103.
Summary of compatible, currently available, parts for 4.5” Diameter Motor Lower Unit Repairs:
Motors Made After 7/2019, or w/Updated Center Sections:
Motors Made Prior to 7/2019 and without Updated Center Sections:
