Johnson service bulletin archive / Dealer Letter #194

Johnson vs Michigan Wheel Bazooka Hub Propellers - 1969 Comparison - DL-194

Johnson responded to reports about Michigan Wheel “Bazooka Hub” propellers by describing its own comparative tests. Both designs produced nearly identical speeds in the tested installation, but Johnson reported severe ventilation with the Michigan propeller when the motor was raised and tilted. The letter also includes a separate correction to the 1969 special service tool catalog.

Original Johnson Motors red Dealer Letter letterheadDL-#194

May, 1969

SUBJECT: PROPELLERS

Some of you may have received conflicting or confusing reports on the effects of using Michigan Wheel "Bazooka Hub" Propellers on Johnson engines. In order to verify or disprove these stories our engineers tested the Michigan propeller and compared its performance with the comparable Johnson propeller.

The engine was set up for the test with the stern brackets resting on top of a 20" transom and the anti-cavitation plate parallel to the boat bottom. The results of this test showed that the boat speeds obtained with either the Michigan Wheel or the Johnson propeller were nearly identical. We did find, however, that the converging ring on the Johnson propeller allowed us to raise the motor on the transom and tilt the motor out to gain added boat speed without running into ventilation (cavitation) problems. When we attempted these changes using the Michigan Wheel propeller, severe ventilation was experienced. (This testing was limited to 17" and 19" pitch propellers and the results do not necessarily apply to other size propellers).

Reports from the field verify our test results in that excessive ventilation on some installations has been eliminated by replacing the customers Michigan propeller with a Johnson propeller.

Original Johnson Motors signed signature block

DC:rm

CORRECTION: On Page 8 of the Johnson Special Service Tool Catalog for 1969, part number 312435 Clamp Button Fixture should read part number 302435.

Related factory publications

The original comparison was limited to 17-inch and 19-inch pitch propellers. The separate catalog correction changes the Clamp Button Fixture number from 312435 to 302435.