OMC 3hp Lightwin – JW gearbox- prop

[LeeRoy Wisner]

Got a few questions on The Johnson/Evinrude 1952-1968 3hp motors. I have torn into my 6 motors, along with doing a lot of looking at factory parts lists. At this stage in time, it is about impossible to ascertain which was the original prop to what motor. We can assume by observation, but to be sure is my question ???

What I find is (1) Propellers, there are 2 differnet ones, the 2 blade #203919 & the 3 blade #203120. It seems that the 3 blade was used on the first 3 years of production of either Johnson or Evinrude. And many of the folding motors that I see, have the 3 blade, is this factory or changed later??

(2) In tearing into the gearboxes, I find two different sets of gears. A (what I believe to be) a 1952 or 53 JW10 has a 12 tooth pinion with a driven gear #277362 of 20 teeth. A 1954 Evinrude 3012 also has the same 12-20 ratio & 203120 prop of which I have no reason to doubt that it is not original. A 1957 Evinrude 3022 has a ratio of 17 to 28, gear #277457. The 1966 JW21 & the 1968 JW23A also uses the #277457 gear. Same basic size of gears, just different size/number of (and smaller) teeth.

It is my assumption that the higher gear ratio (although slight) gear boxes use the 3 blade and the lower ratio the 2 blade props. HOWEVER, I cannot find any quick reference as to which motors/years used which prop, therefore asking for assurance/help.

Marked on props 2 blade #203919 6 1/4″ X 5 1/2″ BUT on some listings it shows 6 1/8″ X 6 1/4″ misprint?
” ” ” 3 blade #203120 6 1/4″ X 5 3/4″
JW23 2 blade prop #203919
JH series 3 blade prop #0312286 Replaced by 0315858 8 X 5 1/2 as JW do not have enough clearance for the 8″
I do not have access to a JH motor to be able to count the gear teeth.

The reason this popped up is when I was restoring a VERY EXPERIENCED JW10, which now wears the powerhead off a 3022 Evinrude. The JW10’s lower unit had a broken exhaust extension, so I was trying to easily swap the a 3022 but later found it had a bad mid-section, so back to using the best of both & found the different drive gear of the JW10 would not mesh with the Evinrude driven gear. Finally got it figured out, and it now running, but it now wears parts off 7 motors, thanks to eBay for some starter parts.

(3) My question, why did they make the change as the size of the props is so close, and the gear ratio is also close. Therefore if they were swapped, what difference in performance would a person notice, probably minimal? The smaller teeth would not be a strong. But why the change unless the new gears were off another later companion model?

OH YES, I finally figured out how to get that driven gear thrust bearing (Nylon) #203140 out of the housing? On the motors that I worked on, it had to come out in order to get the drive gear out. I tapped the center hole to 1/4×20 & then threaded a long rod (you need at least 6 1/2″) into it (the hole), pushing the bearing out !!!

Also FYI, the starter pawl system of these early 3 years is also different than the later motors.

[aquasonic]

Six motors apart at the same time! That would, to say the least, be confusing for some of us.

Regarding the different starters, there are two types. The Simplex starter, for the 3 Hp, was used from 1952-1955. In 1956, the Eas-A-Matic starter was introduced, with the elliptical pulley, which made it possible to turn over the motor with less force.

As far as the different props go, the earlier props were three bladed as you had mentioned. My limited understanding is the change from the 3 blade to the 2 blade props occurred because the earlier 3 blade setup had a tendency to over-rev, causing connecting rods to break.

The minor changes in the gearing may also be related to the over-rev issues. I’ll be interested to see what others have to say.

 

[frankr]

I didn’t take time to wade through all the facts and statistics you mentioned. but it should be noted that JW and JH models are totally different purpose-driven motors.  JW, is, of course, the angled weedless drive designed for shallow and weedless waters inhabited by fishermen.  On the other hand, JH motors have straight 90 degree drive with larger/flatter props, designed for high thrust on larger boats.  Indeed, Evinrude named theirs as “Yachtwin”, suggesting sailboat auxiliary use.  Apples and oranges.

[fleetwin]

Likewise, didn’t research all the points you have mentioned.  But, I have noticed that the earlier three blade props used on early 50s models weedless 3hps seem to be slightly less pitch than the later 50s models through the 60s.  Again, I would have to actually research this to see if my observation is correct.  I was not aware that the gears/ratios changed slightly either, but that is entirely possible.  Again, we are speaking about the weedless drive models, not the right angle models.

The two blade props used for most of those years seems to be slightly more pitch than the 3 blade props that were introduced on the 4hp models in 69.  In most cases, these engines are incapable of planing a boat, so trying to compare top speeds seems pointless.  What prop do you have now?  If you have the original three blade prop, go ahead and try it.  Replace it with the 2 blade prop if the engine seems to over rev slightly.

[frankr]

[LeeRoy Wisner]

“As far as the different props go, the earlier props were three bladed as you had mentioned. My limited understanding is the change from the 3 blade to the 2 blade props occurred because the earlier 3 blade setup had a tendency to over-rev, causing connecting rods to break.”

That may also partially explain why these motors have a “bug catcher” carb restricter between the carb & silencer.

I will be picking up a folding Yachtwin within a couple of weeks for more comparison.

This series of motors is new to me, but I am learning

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