1981 Evenrude 25HP proper prop

[flywelder]

I have a used 1981 Evenrude 25HP outboard, model # E25RCIM and I'm wondering what the proper propeller for it would be, as I am sensing that the prop on it now is incorrect, for the prop on it now, is brass, and has no rubber splined, insert/hub, just a brass prop that is master grooved/splined. Is this the proper/ factory prop? or what wold be the correct prop for me to buy?

 

[jimmbo]

No, it certainly is not the correct Prop, unless you are using it on some kind of little Race Boat, then it might be.
OMC never marketed Marketed Bronze Props for that engine. They did market 2 SST props for it though,

As for what is the correct Prop, well that will depend on what the Motor is used. A Tachometer will be needed to determine which is the correct one, which will allow the engine to run in its Recommended RPM range at WOT, which for your engine is 4500 - 5500. There are small Inductive Tachs available that you can use

OMC had about 7 props for that engine, ranging in Pitch from 7" to 12" in one inch increments. I'm sure there are still props from both BRP and 3rd parties available

The prop that shipped with the 81 25hp was an AL 9 1/4" X 12", up one inch from 1978 - 1980 engines, which shipped with a 9 1/4" X 11"

 

[jimmbo]

I had looked in the 1981 Evinrude Brochure and it said 9 1/4" X 12", looking the 1981 Johnson Brochure, and it say 9 1/4" by 11".

 

[flywelder]

Terrific information!! thank you very much!! The engine is on a 1980s something 16 foot long, Dixie fishing boat, fiberglass. I use the motor to just get to fishing spots on the local lakes. I'm very happy you included the info from the 1981 brochure and that it was shipped with a 9 1/4 x 12" prop. I will seek one of those in aluminum. Thanks again!!

 

[flywelder]

Oh I forgot, to ask, did the brochure say the prop was a 3 blade or a two blade? and is the proper prop, a RH or LH ?

 

[jimmbo]

3 blade, OMC never Marketed a 2 blade for it. Michigan Wheel probably made some 2 blade ones. All the props for those engine were RH.

I think a 10" pitch would be closer to what you will need


The Evinrude Brochure said 9 1/4 X 12, the Johnson said 9 1/4" X 11. We had a 79 25hp Evenrude and it came with the 11, and we were using it on a 14 ft car top. and it was within the RPM range. We also had another of the same boat with an 80 35 hp

Pic was early June 1981, wow 39 yrs ago

 

[flywelder]

Oh a 10 inch , okay, I'll hunt for one of those,even used and decent is fine. Thanks again!

 

[Texasmark]

3 blade, OMC never Marketed a 2 blade for it. Michigan Wheel probably made some 2 blade ones. All the props for those engine were RH.

I think a 10" pitch would be closer to what you will need


The Evinrude Brochure said 9 1/4 X 12, the Johnson said 9 1/4" X 11. We had a 79 25hp Evenrude and it came with the 11, and we were using it on a 14 ft car top. and it was within the RPM range. We also had another of the same boat with an 80 35 hp

Pic was early June 1981, wow 39 yrs ago

Off topic but response to a valid posting: Are those Mirror Craft boats? I had a 14' , big and wide, with a classic Merc. Mark 30 remote I found used. Nice little light weight boat for smaller waters and easy to get around places. The 30 was just right for a good ride to and from the fishing spots.

 

[flywelder]

I pulled the bronze prop off. and after cleaning I found this info on it:
Michigan PR 423 .
Has any one any info on this prop? such as: age; pitch; diameter; maintenance needs ?

 

[jimmbo]

My Michigan Catalog shows PR 423 as a Bronze 3 blade, 8 3/4" X 10"

 

[flywelder]

Oh! !!! and wow! so, the bronze is a 8 3/4 x 10!! wow! very interesting! has me wondering why Michigan made a 8 3/4 x 10 and not made it 9 1/4 x 10 ??? half an inch difference??:noidea:

Jimmbo suggested 9 1/4 x 10, and evenrude says 9 1/4 x 12 .

Now, I want to know, do you feel, there could be a significant and actual notable difference felt,/ sensed, between the 8 3/4 x 10 and the 9 1/4 x 10 ? That Would justify purchasing a prop? Or put the money back for some future, and unexpected repair!?

I doubt I could tell a difference, if I didn't know I was comparing,/ actually testing and comparing two, slightly different props against each other. maybe others could, but, I am no expert or have any experience with props either.

Then, as I think on it, Evenrude is in a good position to test different props on each motor, and if they thought 8 3/4 was enough or best they wouldn't suggest 9 1/4. mmm? Much to consider! Looking forward very much to reading your thoughts! they will mean, and help, a lot!

 

[jimmbo]

Michigan had prop Engineers who worried about the Diameter, The Blades are only a 1/4" different. I would continue running the Michigan, as the Bronze Prop likely has thinner but stronger blades than the AL. The downside is it is a lot heavier than the AL, Heavier than SS. and that can accelerate Wear on the Clutch Dog and Gears, especially if shifting is done too slowly.
Without seeing the Props side by side, I can't compare Blade Shape, Area or Contour,

 

[flywelder]

Excellent info! Great reading! I felt certain you would have some! I was unaware of the items you mentioned! Now, your comment on shifting too slow..... I thought that would be better to do! yikes!

I wish there was a video to watch that was a great example of just what speed to shift in and out of forward and reverse!!

 

[jimmbo]

Best speed to shift into gear at, IDLE. Shift Quickly.

 

[flywelder]

Okay shift quickly. Thanks! Another question: the prop needs to be tight on the splined shaft? No sliding back and forth on the splines. correct? So, the prop nut, needs to be spun up tight against the prop,and still line up the hole for the cotter key, correct?

 

[Texasmark]

Okay shift quickly. Thanks! Another question: the prop needs to be tight on the splined shaft? No sliding back and forth on the splines. correct? So, the prop nut, needs to be spun up tight against the prop,and still line up the hole for the cotter key, correct?

To answer that question, my 100 hp viscinity Mercury service manual says torque prop nut to 55 ft#. Slop would just "wallow" out parts and lead to problems later on. If you have a Castle Nut, which sounds like the case, if, getting the nut tight, there is no room for the cotter pin to remain in the nut's slots, you will have to insert a shim washer between the nut and the prop, or you have the wrong thrust washer on the prop shaft that the front end of the prop rests against and it is allowing the prop to move too far forward on the prop shaft causing the problem.

 

[flywelder]

Thank you!!
Oh! so, a 'thrust washer' is used / required on the shaft between the gear housing and the prop! Or washer between the prop and the nut! interesting!
Could a thrust washer be placed on both sides of the prop? and that be okay? Just seems in my mind, to be a good idea for a bit of 'cushioning effect'?

 

[flywelder]

Would any one have and would share with me a link to exploded pictures of the different sections of my evenrude motor, THAT, listed all the parts identified, NOT just identifying the parts still available to purchase! That would be helpful to have such reference material.
THEN, is there any means for me to attach that info, or/ link, to my profile HERE on this forum,? so I can refer to it quickly, just by clicking, and not having to search the web for it time after time? My engine is a 1981 E25RCIM

 

[jimmbo]

Your 20 hp uses a Splined Drive, It may have a Pin in place of a Thrust washer or the prop just bottoms out on the splines(It has been almost 40 yrs since we had the our 25), Just snug the Prop Nut till the Holes for the Cotter Pin Line up.

Edit: Parts List show neither a Pin or a Thrust Washer.