Prop. Swap Options --NOT TRYING TO BE CHEAP-- :-) Just efficient!!

[imported_Samuel]

Hello-

I have a 40HP Lark VI (1964). I am looking into prop. issues, such as replacements etcetera. This motor has a pin drive, with a ¾ inch shaft, no splines (except the 2 positioning cut in on wall).

OEM prop has a base height of 3 inches. So as I look, I find many great used props., pin drives, but with a 7/8 hole. They appear to fit in all other specs., but would be loose if installed. Thus the question(s) below:

“If I find a prop. That is a slightly larger diameter, say 7/8, can I shim the prop. , making sure it is concentrically centered?”

“Will the shims increase damage potential?” “if so, why?”

Yes, I can find new props to fit, but they are aluminum or Very Very expensive if S/S. I need a SS prop. due to the fact that the lake I run in has a sandy, silt bottom with lots of shallows and “hidden treasures”…

Not trying to be cheap. But necessity (and a not too fat checkbook) is /are the mother(s) of invention.

Related Q:? Can I use washers or pipe (use as a sleeve) with washers at each end as a base extension should the prop. be less than the 3” inches the original is?

Many Thx.

Sam

 

[walleyehed]

Re: Prop. Swap Options --NOT TRYING TO BE CHEAP-- Just efficient!!

All 1960-1974 40 JohnRudes used the same props...they all have 13 spline pin drives.
If you have something with no splines, this is the first I know of it on these models....
Are you sure the small cone-shaped hub is not missing?

 

[imported_Samuel]

Re: Prop. Swap Options --NOT TRYING TO BE CHEAP-- Just efficient!!

Walleye-

I had a good look at the shaft and it appears non-oem...just 2 holes for the shear pin and one for the cap & cotter pin that holds the shear pin in place.

There are no splines at all....since the holes on the shaft are centered, but oblong, I would guess that they are after market, since they look drilled.

Other than that described above, the shaft is smooth all the way to the lower unit seal.

I guess it must have been rigged by a creative prior owner.

Thx

Sam

 

[walleyehed]

Re: Prop. Swap Options --NOT TRYING TO BE CHEAP-- Just efficient!!

There was one shaft made that I found, that uses 2 tabs for alignment, with no splines.....if this is the prop you have, we may be in trouble.
Let me see if I can get the master of this vintage of engine to post on this...hang tight!

 

[Paul Moir]

Re: Prop. Swap Options --NOT TRYING TO BE CHEAP-- Just efficient!!

That's the normal prop style for Big Twins (25hp '51-55, 30hp '56, 35hp '57-59, 40hp '60-76, commercial '78-'85, 28hp '62-'64, 33hp '65-'71 ) They are a smooth 3/4" bore with pin in one end and two grooves which allow the propeller to be removed if the pin's hole through the propshaft ends up marred.

There is no SS available that I know of with this style hub. Al is available from both Johnson/Evinrude and Michigan Match in a variety of pitches. Since the HP of the Big Twin varied so much over it's run, and the fact they were fitted to all styles of boat, the likelyhood of finding the "right" pitch prop by chance is remote.

That said, I see a bunch for sale on Ebay. Just search for "evinrude propeller" and pick through the non-thru-hub ones. A nice brass speed prop there too.

I believe the 7/8" bore is for the old (60s era) V-4s, but I don't know much about them. They will not suit your Lark. Not only will the pitches be off, but the diameter is too large to fit under the anti-ventilation plate.

But your average J/E dealer or outboard junkyard will have scads of these since they were so common. Do not pay much as they don't have much value. Check tcoutboards.com, laingsoutboards.com, etc, etc.

Check your prop for a number. If you don't find one on one of the blades, it's an older prop. Check the area under the thrust washer (just beyond the pin). If you don't find one there, flip it over and check the area between the outer aluminium casting and the brass hub. If you don't find a 10-3/8x12 (say) then you'll find a six digit number starting with 3.

Can you tell us about your boat a bit? How heavy (ideally), what style, what size? We should be able to get you in the ballpark for pitch with that.

Walleyehed: Sorry, normally I try to read through the prop forum to learn a thing or two, but things have been busy lately in the repair forum. I have PMs directed to my email so if I miss one of these just fire me a PM. I think they're working...

Big Twin prop with hub removed:

 

[Texasmark]

Re: Prop. Swap Options --NOT TRYING TO BE CHEAP-- Just efficient!!

Back in those days we ran brass props as well, bought from Michigan Propeller Co. Probably still available.

That !@#$%^&*() shear pin and that stupid lower unit gear box (protruding) were the two main reasons why my garage houses black engines.

Seems every time you needed your engine, like on the windward side of riprap with the wind blowing 30 mph, you'd hit something and snap the pin. Then you're just dead meat.

On the gearbox, couldn't hardly get to stay sealed and always hanging up on something when you're fishing.

Mark

 

[walleyehed]

Re: Prop. Swap Options --NOT TRYING TO BE CHEAP-- Just efficient!!

Paul, thanks for the help!!d

 

[imported_Samuel]

Re: Prop. Swap Options --NOT TRYING TO BE CHEAP-- Just efficient!!


Guys- I sit before you in awe of your knowledge.

My boat is a Triton 15 foot cruiser/runabout. A floating weight of approx. 700#. 4 seats, 18 gallon tank with a 1964 Rude Lark VI, 40HO for power.

Normally run with 275# lbs of passengers and stuff.

The motor as stated above has a smooth bore/shaft for the drive with the following dimensions of the prop./shaft:

OEM Prop. is an Alum. 10" 12 pitch

Shaft 3/4"
Prop. Height (laying flat) 3"
Prop. Diameter rear hub 2 7/8”
Space between outer hub and inner hub 3/8”
Shear Pin dia. 1/4"

I found a new S/S unit with similar dimensions on eBay for 15.00, only the rear of the hub does not appear to be notched. I figure that I can pout a washed between the front of the sealed unit and the prop to maintain the space and reduce direct friction.

Any suggestion or comments on my Shim ideal...I would appreciate.

Note: I ran, quite well I may add, the 7/8 bore brass prop., 10.5 ". I shimmed the prop using rolled aluminum sheet metal inserted in the prop. the I took 3 clothes pin (wooden ones) and inserted them to establish centering of the unit and snugged fit. I cut a new shear pin and it fit through the prop hole and the cotter pin hole on the shaft and I cover this with a tight rubber band to prevent the loss of the pin by centrifugal forces. I ran fine for almost two hours...had some play when I got out of the water...still trying to figure a better shim system so that I would get no play from components coming loose.

Any ideas let me know.

Sam

 

[Texasmark]

Re: Prop. Swap Options --NOT TRYING TO BE CHEAP-- Just efficient!!

Do you have a competent machine shop handy? I do and although I haven't needed them for water projects, I have gone to them many times with agricultural unsolvable problems and was very satisfied with their support, ideas, and unique parts made for me at a very reasonable price. Besides, I found that they like things to stimulate their imagination, and one of a kind type things. Beats the heck out of having to do 300 widgets over and over.

They might could take a piece of 3/4 thick wall (like schedule 40 ) stainless steel or bronze tubing; chuck it up in the lathe, cut the od down to a few thousandts under 7/8, whack it off to length and bingo; got your shim that will last. While they're at it they can drill a hole in it for your shear pin so that the pin can lock it in place on the prop shaft.

Might try it.

Mark

 

[imported_Samuel]

Re: Prop. Swap Options --NOT TRYING TO BE CHEAP-- Just efficient!!

Now that is a plan...

I am happy with the broze prop - 7/8 bore, 10in dia. , 12 pitch (new) i got for 22.00 on eBay, and the new SS 3/4 bore, 10" 11.5 pitch also obtained on eBay for 14.00. Using your suggestion I could easily switch back and forth between them and not be stuck with the all too easily bent OEM Alum. prop.

Much help guys, as always...smooth boating to all8)

Sam

 

[Texasmark]

Re: Prop. Swap Options --NOT TRYING TO BE CHEAP-- Just efficient!!

Great.

Mark

 

[Paul Moir]

Re: Prop. Swap Options --NOT TRYING TO BE CHEAP-- Just efficient!!


Do you know what the SS prop was supposed to be used for?