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Just this morning replaced ten year old 14x17 prop with a new OMC 13.25 x 17 prop and went for a test spin. Speed the same, but engine only turns max of about 4600 RPM. It was 5100 with old prop.

I would have thought a quarter inch less diameter with same pitch would have given me more RPM, not less....

In all, $ 150 wasted.

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Canibul,

Not all props are cupped the same.

Who was the manufacturer of the first 14x17 prop? What model? Part number?

What model and part number of the second OMC prop you just bought?

Also, what size and year of engine are we talking about here? Sounds like a 115 hp engine but I am just guessing. You say the prop was 10 years old so is the motor a 1996 model OMC?

All this information, including the manufacturers max WOT recommendations, will help us determine what the problem might be.

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Dont know who made the first one, but it was pretty dinged up. It has a little plastic cowling thing on the aft end of it. Came with the boat, which has a 96 Evinrude 70 on it. New one is OMC P/N 0763463, which was bought from local Whaler dealer.

I think WOT for the engine is 5500 but not totally sure. I made the mistake of buying the online Seloc manual for it. What a hassle that thing is. try to find a simple spec. Never again.

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Great....

So you have a 1996 Evinrude 70 hp.....

I had a 1985 Evinrude 70 hp and the WOT was stated in the manual as 5000 to 5500 RPM.
I know some of the newer models were rated up to 6000 RPM WOT so I am not sure about yours.

I had two props for my Montauk which had the 70 hp Evinrude on it.
1. 15 pitch OMC prop
2. 17 pitch OMC prop
I got more RPM out of the 15 pitch at WOT and a better hole shot.
I got a couple of more mph top speed with the 17 pitch but the hole shot was slower.
So, I used the 15 pitch on my Montauk and it worked good for me.

Maybe someone here with the newer model Evinrude or Johnson can shed some more light on the subject. It would be good to know the part number and manufacturer of the original prop.
It should be stamped on the inside hub of the old prop or on the outside.

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ok, found it. Inside hub there is an "M" in a leaning diamond shape, as a logo.

There is a small circle with "D2" inside it. Then the number 176214.
and the size 14x17.

Does that shed any light on it?


I would expect higher revs going from a 17 to 15 inch pitch, but keeping same pitch and dropping 3/4" in diameter I did not expect lower WOT.

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I think the "M" would indicate a Michigan Wheel prop but am not positive.

Your thinking would be correct except that different manufacturers use different cup and/or rake on their props.

If you compared a stock 17 pitch OMC prop to a stock 15 pitch OMC prop, then yes, your thinking would be correct.

Here are my OMC prop numbers for my prior 1985 Evinrude 70 hp.
OMC stock Aluminum
13 3/ 4 x 15 # 391198
13 1/ 4 x 17 # 391199

I just did a little research on props at the Bombardier site.
The 176214 is an OMC prop and is 13 1/4 x 17 pitch.
They state that this prop is used on 1999 65 hp models.

I also did a search for the OMC prop you just bought. The 0763463...
This prop does not show up in their database.... Weird....

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The old (nominally) 14" x 17" prop is an OMC aluminum propeller. It is still being made by BRP. The "M" is on most old OMC props. I am not sure what it symbolizes, but it is an OMC logo.

Part #763463 is an old OMC aluminum prop that is 13-3/4" x 17" and is no longer made by BRP.

The difference in performance between the two could easily be attributed to the old prop being rebuilt and altered. The previous owner (or some other) may have had a prop shop re-pitch it or it may be that in removing nicks and dings, enough blade area was removed that it offered less resistance and spun higher.

Unless you are comparing propellers within a specific line of props, simple diameter and pitch can not be used for predictions except in very general ways. The only really good way to know how a propeller performs on a given boat is to go it and run it.

If the "new" prop wasn't satisfactory, just return it. It was old stock anyway, as OMC went out of business six years ago.

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sad, but it doesnt work that way here. I am stuck with the new prop. Its used.
And I dont think I can throw $ 150 a shot to try them out one by one and build a prop collection.

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You need to find a new dealer. You have also discovered why it is best to always "try before you buy".

As it is, just sell your "new" prop on Ebay and take the proceeds and apply them towards something more appropriate, a BRP # 391198, 13-3/4" x 15" aluminum propeller for example.

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sigh. there is one boat dealer in this nation. One.

Ebay never an option, either. I'm stuck with it.

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Seems I been seeing lots of this we all want performace to our needs .

I did a few searches and found Iboats.com http://www.boat-props.com/ and http://www.discountboatpropellers.com

http://www.piranha.com/show_article.php?id=4

from the saddle

Bill

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Bill...I thought you were a brother!!