Johnson Service Bulletin SB-793 - Pump Housing Assembly

The pump housing assembly used on the thermostat equipped 35 H.P. and current 40 H.P. engines was recently redesigned. By incorporating a new vent system in the pump assembly the life of the pump has been extended considerably. It will now tolerate greater wear to the housing or impeller before its pumping ability is adversely affected.

This modified vent system has resulted in changes to the following parts:

377533 Impeller Housing and Seal - Obsolete - superseded by 378348 Impeller housing assembly complete (Fig. 1).

The following parts have been modified to fit both the new pump housing and also to service the old housings. (Fig. 2).

307955 Gasket supersedes 305491 307954 Cap supersedes 305503

The old gasket 305491 and cap 305503, Fig. 2, can still be used to service the old housing. However, due to changes in the vent system they will cause failure in the water system if used on the new style housing.

NOTE TO FIGURE 2: Note different locations of vent holes in pump housings indicated by arrows. Also note 2 vent holes in new style gasket #307955 and cap #307954, while only 1 vent is in old style cap #305503 and gasket #305491.

This change does not make this pump assembly immune to damage or accelerated wear due to excessive silt content in the water. For this condition, where any pump assembly wears and fails prematurely, the chrome pump assembly is specifically suited and recommended to insure longer life.