Reply To: Shaking at High RPM Running 1955 Evinrude Fleetwin Aquasonic 7.5HP

[fisherman6]

Good-Fishing wrote:

Just finished pulling the gearcase. Everything looks alright besides the bearing which was obviously letting the water in so i pulled it. The only trouble the bearing gave me coming off was at the end of the shaft where you place the cotter pin it was sticking. Other than that no problems and it looks straight. The prop i bought NOS in original box because the other one was ruined. Since when you use the old one it just spins and you dont move.

When you are referring to the bearing I’m assuming you are referring to the prop shaft bearing head which contains the prop shaft seal. Could you tell if the water was getting past the shaft seal or between the bearing head and the gearcase? There is always a burr on the prop shaft where the drive pin and the cotter pin go through. I always file them off first to prevent gouging the shaft bearing and possibly damaging the shaft seal if it is still serviceable.

When you say the old prop was ruined because it just spins and you don’t move, I’m not sure what you mean. Does the propeller spin when the motor is in gear and running and it just will not push the boat? is the propeller just spinning around the prop shaft and not turning in the water? I’m assuming it must be the first scenario since there is no rubber hub or clutch in this prop, only a drive pin that passes thru a hole in the center of the hub extension and the prop shaft. There is a strong possibility that you may have sprung or broken the shock absorber in the top of the gearcase. These things tend to get more brittle as they age. If this is bent / broken / rubbing the bottom of the drive shaft bearing carrier that may be causing some of your vibration also. When these break I squeeze them back together in a vise or a press and weld the seam together. This eliminates the shock absorber effect and necessitates replacing the steel drive pin with a brass shear pin to protect the gears, but it will not destroy the bearing carrier for the drive shaft and it will not break unexpectedly in the middle of the lake and leave you stranded. While a shear pin is not the easiest thing to change on the water, it can be done and you can get back home. If the shock abosrber breaks you will be rowing or getting a tow.
-Ben

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