1976 johnson 40hp

I have a 1976 Johnson 40hp that starts up and runs great, however anything past half throtle causes a slip in the motor(feels like its coming out of gear)
I have had the prop tested and replaced with a brand new prop(both were tested and are not spun)I have taken the lower end apart and found a bearing that had come apart, I repacked the bearing and still have the same problem.gears look good.According to the scematic there are thrust washers above the bearing i repacked, they are hard to check but look worn.ANY IDEAS!!!!!!!!!

Re: 1976 johnson 40hp

is it a slipping or a bang or thump, like you hit something underwater?

Re: 1976 johnson 40hp

MARIJAM729 said:

I have a 1976 Johnson 40hp that starts up and runs great, however anything past half throtle causes a slip in the motor(feels like its coming out of gear)
I have had the prop tested and replaced with a brand new prop(both were tested and are not spun)I have taken the lower end apart and found a bearing that had come apart, I repacked the bearing and still have the same problem.gears look good.According to the scematic there are thrust washers above the bearing i repacked, they are hard to check but look worn.ANY IDEAS!!!!!!!!!

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You are talking about the pinion roller bearing?? It is normal for that to fall apart if you remove the pinion. It ain't broke.

If the thrust bearings were so bad as to allow slippage, there would be obvious catastrophic damage to the gears. You say the gears look good, so that isn't broke either.

That leaves the question just asked..Does it jerk, bump, and grind? If not, there are only two things that can slip. One is the prop hub, which you have eliminated. The other is cavitation or ventilation. In reality, they are both the same thing...air around the prop.

Re: 1976 johnson 40hp

The motor does not bump or grind. If i put the motor past 5mph the motor races and you get spurts of power(feels like if you were in a car and trans was going bad) I haven't checked the ventalation around the prop, how would i do that?
And yes it was the pinon roller bearing that had fallen apart.
Its a shame because this motor has low hours and starts every time

Re: 1976 johnson 40hp

There isn't any way to "check" for ventilation. It's just one of those things that you feel and recognize from experience. Could you get somebody that knows to take a ride with you?

First question I have to ask is it a short shaft motor on a long shaft transom? That would be the #1 obvious cause.

Other than that, ventilation is usually caused by jacking the motor up too high on the transom in an effort to get more speed. That lower unit in that motor was designed 60 years ago, when boats were made of wood and had keels. The anti-cavitation plate has to run well below the boat bottom or it will ventilate. You simply cannot jack them up like modern designs.

Another cause is anything that changes the flow of water to the propeller. Can be weeds, marine growth on the boat, some sort of add-ons on the motor, and anything else that I can only guess at.

Invite somebody experienced with high performance boats to take a ride.