1961 Lark iii 40hp

[steve17]

Over the weekend I was out on my boat and when I took the throttle to full speed it sounded like the prop was just spinning and at the same time I was going no where. After doing so research I figured I needed a new prop. But after taking the prop off (for the first time) I looks like I'm missing a key that should be on the drive shaft. At the same time it looks like the cap that's on the end of the prop has a notch that fits onto the groove in the drive shaft the prop sits on. I think that I need to order the key, but am not completely sure since there is a notch in the cap. I've never pulled the prop off before so I'm not sure exactly what I'm missing. Just like I was told that there should be a rubber bushing on the prop, which of course there isn't. I was wondering if anyone had any knowledge of what the issue maybe?
Thanks

 

[HighTrim]

Re: 1961 Lark iii 40hp

There should be a drive pin which locks the prop to the prop shaft. If it is not there, you will have no movement but will hear the motor rev up. #4 in the diagram

Evinrude Gearcase Parts for 1961 40hp 35525 Outboard Motor

 

[steve17]

Re: 1961 Lark iii 40hp

When I took the prop apart the drive pin was in place. I found this diagram and have been trying to study it to figure out if I was missing something or not. Thats when I noticed the notch in the end of the prop shaft and was thinking there maybe something that should fit in there?

 

[bad coffee]

Re: 1961 Lark iii 40hp

Hightrim, thanks for the link. I'm about to rebuild a '56 Lark.


B

 

[HighTrim]

Re: 1961 Lark iii 40hp

If your drive pin is intact, your prop is spun.

Draw a line across the hub to the prop with a sharpie. RUn the motor till it revs. Then pull off the prop. If the lines are no longer lined up, the hub is spun and will need to be rebuilt.

 

[F_R]

Re: 1961 Lark iii 40hp

When I took the prop apart the drive pin was in place. I found this diagram and have been trying to study it to figure out if I was missing something or not. Thats when I noticed the notch in the end of the prop shaft and was thinking there maybe something that should fit in there?

The slot and key molded into the plastic nut are to keep the nut from spinning off in event of a broken drive pin. The big groove in the prop hub with no matching slot in the shaft is to provide for spinning the hub into the prop at the factory. There IS a rubber bushing, you just can't see it. It is a donut between the brass hub and aluminum prop body. The rubber is bonded to the brass and a friction grip between the aluminum. If it breaks loose from the brass it slips and spins......as you experienced

 

[steve17]

Re: 1961 Lark iii 40hp

Okay tested and my prop is spun. Does anyone know where I may find information on what the pitch of my prop should be?

 

[steve17]

Re: 1961 Lark iii 40hp

I found the props offered through iboats. Is there any pros or cons to either? Ones the 12" pitch and the other is 11.5" pitch. I would assume there isn't much diff. Between the two since there so close in pitch and diameter. Any thoughts

 

[HighTrim]

Re: 1961 Lark iii 40hp

More depends on your boat and setup and use. The main thing is that your WOT RPM falls within the recommended range. 0.5" pitch difference will only be about 100RPM difference. As you increase the pitch by 1, you decrease the WOT RPM by about 200 RPM. Likewise, as you decrease the pitch by 1, you increase the WOT RPM by about 200RPM.

 

[steve17]

Re: 1961 Lark iii 40hp

Okay. I have a 65 starcraft Bahama its a light a boat and right now zips down the lake nicely. I use it mainly for tubing and cruising the one thing I don't know is if I'm running at WOT or what my RPMs are at since I don't have a tach so I guess that will have to be something I will have to look into.