Spun Prop on 1962 10 hp?

[BSDenning]

I've got a 1962 10 hp Evinrude Sportwin (model number 10024). I've got it on a 14ft jon boat rated for 3 people. Recently, I was running the motor at wot on the river with the boat weighed down pretty good (3 people in the boat and gear for fishing). The motor was running fine and then it revved up. I backed the throttle down and the RPM's dropped. Then I brought it back up to wot and the same thing happened again. I backed it off and it ran fine at a lower throttle. Later in the day, I ran it at wot and it didn't give me any problems.

Anyway, the symptoms sound to me like a spun prop, but this motor has a drive pin (shear pin) in it. Is it possible to have a spun prop on a motor with a drive pin? It seems like the drive pin would keep the prop from slipping.

 

[F_R]

Re: Spun Prop on 1962 10 hp?

Take a closer look at the prop. There is the aluminum blades portion and a bronze center hub. What you can't see is the rubber ring between the bronze hub and aluminum blades portion. It is that rubber ring that tears loose and then the bronze portion spins without turning the blades. The drive pin only drives the bronze hub.

They usually don't self heal. Since yours seems to have healed, it probably was just cavitating. Try it some more and see if you can get it to slip.

Make a mark on the prop, and another on the prop nut, aligned with the first mark. Then run the motor till the suspected slippage occurs. Stop the motor and look at the marks. If they are no longer aligned, it slipped.

 

[tashasdaddy]

Re: Spun Prop on 1962 10 hp?

here is a bigger prop

 

[BSDenning]

Re: Spun Prop on 1962 10 hp?

Thanks for the explanation F_R! What exactly is cavitation? I thought that happened when the motor was not far enough down in the water.

I will try what you said about marking the prop to see if it moves.

Is there any chance that the prop could completely spin off the bronze hub while I'm running it? What I'm asking is, should I be worried about losing my prop in the water.

 

[tashasdaddy]

Re: Spun Prop on 1962 10 hp?

it could in reverse.

 

[BSDenning]

Re: Spun Prop on 1962 10 hp?

Oh, I see, because in forward, the prop is pushing forward toward the motor. In reverse it would be pulling backwards away from the motor. Thanks Tashasdaddy.

 

[1946Zephyr]

Re: Spun Prop on 1962 10 hp?

You might check your shift linkage adjustment, to make sure you're not jumping out of gear

 

[F_R]

Re: Spun Prop on 1962 10 hp?

cavitation is air bubbles around the prop. There are many causes including improper depth, weeds fouling the lower unit, boat bottom, etc, etc. Here in Florida, weeds are a MAJOR problem and everybody around here knows about cavitation.

 

[BSDenning]

Re: Spun Prop on 1962 10 hp?

You might check your shift linkage adjustment, to make sure you're not jumping out of gear

How do I do that?

 

[BSDenning]

Re: Spun Prop on 1962 10 hp?

cavitation is air bubbles around the prop. There are many causes including improper depth, weeds fouling the lower unit, boat bottom, etc, etc. Here in Florida, weeds are a MAJOR problem and everybody around here knows about cavitation.

Ah, ok. Does cavitation also happen when you follow closely behind another boat?

You know what, now that you explained to me about cavitation, I bet that was what was going on because there were a lot of leaves floating in the river that day. I bet I could have got a pile of leaves stuck in front of the prop and caused cavitation.

I took the boat out today and I had no problems.

Thanks a lot F_R!

 

[F_R]

Re: Spun Prop on 1962 10 hp?

Anything that disturbes the water and causes air bubbles ahead of the prop can cause cavitation. Here in the salt water bays we have what is called sea grass. Just one lousy 12-18" blade of that grass looped around the gearcase can cause cavitation on boat/motor combos that are prone to it. Then in fresh water we have water hyacinths, hydrilla, pepper grass, and a mess of stuff I don't know the name of. Boating through it can be a battle. You have to keep stopping, put the motor in reverse to clear it and then go forward to the next clump. Anybody mention worn out shifters?

 

[TN-25]

Re: Spun Prop on 1962 10 hp?

Anything that disturbes the water and causes air bubbles ahead of the prop can cause cavitation. Here in the salt water bays we have what is called sea grass. Just one lousy 12-18" blade of that grass looped around the gearcase can cause cavitation on boat/motor combos that are prone to it. Then in fresh water we have water hyacinths, hydrilla, pepper grass, and a mess of stuff I don't know the name of. Boating through it can be a battle. You have to keep stopping, put the motor in reverse to clear it and then go forward to the next clump. Anybody mention worn out shifters?

That is exactly how we experienced weed fowling on our 9?. We would then stop, run it in reverse to shed the weeds, then continue in foreward without a problem until the next marshy area. We never had that problem with the Johnson weedless 3-horse (they really work!)

 

[BSDenning]

Re: Spun Prop on 1962 10 hp?

Well, I learned a lot from this thread. Thanks guys!