looking for specs on propeller: Mercury 48-79572-17

[Neutron68]

I'm looking for a manufacturers web link to specs, please.

Thanks,
Eric

[WetRaider]

I don't know of any Merc table off hand ... if I remember right, the 48 is a manufacturer ID - the 48, I think, is for Quicksilver (if it's older, it's Quicksilver by Mercury - this seems to be an older number)
The obvious part of this number is the 17.  It's a 17 pitch, or 17 inch pitch ... this means for every 1 full revolution, there should be 17 inches of forward movement (in a perfect world, with no slippage).
A quick google search shows many other props with the same number coming up ... all seem to be a 15 inch diameter prop, aluminum, 3 blade, Right Hand rotation

[Neutron68]

That's odd.  I searched Google and didn't find any manufacturer's information.  
Can you quote the links you found, please?

Eric

[Hyperacme]

Mercruiser 15 x 17

[WetRaider]

Cool, Gregg ... where did that chart come from?

The information I saw was posted on other forums ... a SeaRay group, iBoats, etc., along with eBay listings for the same part number (took me mainly to spanish language eBay sites, which may be why you aren't finding much in a domestic search).

Mercury parts numbers generally start with 48 for Quicksilver parts, 50 for Mercury ... there may be some others, but I've only had experience with those two.  The middle group of numbers is the "real" part number.  Most Mercury parts dealers can find what you're looking for with only those numbers.  Not always, though.  The last two is the pitch.  For some period of time, Mercury was stamping their part numbers with a "P" after the last two, to indicate pitch.

This group is full of many Mercury Geniuses - my experience is limited, the collective experience from this group  is amazing, though.

[Rich_V174SS]

Mercury parts numbers generally start with 48 for Quicksilver parts, 50 for Mercury

To my knowledge not so ...

All Mercury and Quicksilver props start with the prefix 48 to identify the class of the part, in this case a propeller. Parts that begin with the prefix 50 are starters.

[Neutron68]

From the attached image files, it looks like the closest part number is 48-79572A4 which is a 15 3/4 diameter x 17 pitch.
Is that the way the rest of you read that?

I want a 15 inch prop for a 1978 Mercruiser 120.  Won't a 15 3/4 be too big?

Eric

[WetRaider]

All Mercury and Quicksilver props start with the prefix 48 to identify the class of the part, in this case a propeller. Parts that begin with the prefix 50 are starters.

Thanks, Rich.  Sounds much more reasonable.  Merc Genius. 

[Hyperacme]

Attached image was a clip from a PDF of a Michigan wheel brochure ...

http://www.miwheel.com/

http://www.miwheel.com/propellers/resources/downloads/

15 3/4 is Dia.
17 is Pitch

What Glastron do you have ?

[Neutron68]

I've got a 1978 Glastron SSV-177 (17 foot long) with a Mercruiser 120 engine and strern drive serial number 4906558.

[Rich_V174SS]

What is it you want to do? What kind of rpm and speed are you getting with your prop at full throttle?

When I had a Mercruiser 120 in my V174 I was using a 14x21p prop and getting around 4600 rpm. The boat would go 36 mph with an aluminum 21p prop and about 40 mph with a stainless 21p prop. I would think a 17p prop would not be enough and cause you to over-rev the engine at full throttle.

[Neutron68]

I just got the boat in June 2013.  The previous owner had put an13x19  outboard propeller on the boat.  I had t he lower unit seals redone and the service shop manager said I should have a 15x17 prop on there.
I plan to take nice easy cruises around the lake for the most part.  It would be nice to be able to go fast at times.  Maybe sometime in the future I might consider pulling an innertube.

With this 13x19 prop I have seen 4500 - 4600 rpm at full throttle.  The mercruiser manual says 4300 should be the max.  A bigger prop should slow down the rpms, yes?

Eric

[Rich_V174SS]

If you were getting 4500-4600 rpm with the 19p I would leave that prop on. Less pitch would give you more rpm, more pitch lowers rpm. I'm not sure what the 15x17p prop will do because it has a larger diameter versus the lower pitch, it may end up being the same as the 13x19p. Try it and see how it performs for you, rpm vs. speed.

[Neutron68]

The boat came with a beat up 15x19 prop as a spare.  I suspect they put the 13x19 outboard prop on as a stop gap measure.

I'm about to buy this presumed 15x17 prop for $75.  Its either new or it was reworked and repainted.

Eric

[Neutron68]

Here are some photos to go with the previous descriptions.

Here is the 13x19 prop that came on the boat and is still on the boat at the moment.



Here is the 15x17 prop I just bought (left) and the beat-up 15x19 prop that was included with the boat.  
I wonder if the 15x19 was the original 1978 prop?



The seller of the 15x17 prop said it is a 1979 vintage and has been in his boathouse near Annandale, MN for the last 20+ years.
It sure has WIDE blades, compared to the 15x19 prop!
What do the wide blades do for you?  Torque and fast starts?

Eric

[75starflight]

Eric, I have a mercruiser 120 running a laser II 14x21p on my 1975 v179 starflite tri-haul. I have a Max rpm of 4300 running 43mph. This boat originally had a 14.5x19p aluminum on it and I would turn between 4600 and 4800 rpms. It also did this with a stainless 19p. I would steer clear of the 17p.

Just some flood for though, at the red wing meet I had four adults on board 2 coolers and some folding chairs and had no problems getting on plain and it seems to have great pulling power also.

[Neutron68]

Well, I've got the 15x17 prop now.  As Rich_V174SS suggests, I might as well try it and see how it performs.

The Mercruiser 120 manual says the RPM WOT should be 4300.  I've been seeing 4500-4600 with the 13x19 prop.  From what I understand, that RPM rate is too high for this engine.  I have to believe that a bigger diameter prop will offer more resistance to the engine.  If so, the prop should turn slower with a bigger prop.  So, going from a 13 inch diameter to a 15 should lower the max RPM.

Eric

[Hyperacme]

It's hard to guess what a prop will do until you try it ...
If the one you got won't work ... put it on Craigslist and try another size.
You could ask members if you could borrow one and try it.

or

Supreme marine has loaner props, but just SS.

http://www.suprememarinemn.com/

[Neutron68]

What should I do with the beat-up 15x19 prop?  Should I pay to have it reworked and use it as a spare?  Would it be worth anything on Craigslist if I didn't want it?

Any idea why the blades are so narrow and swept back?  Is this some kind of high-speed prop?

(the 15x19 is on the right)
http://i870.photobucket.com/albums/ab264/neutron68/Glastron/20130916_195426_zps03c671dc.jpg

[Rich_V174SS]

That 13x19 prop that is on the boat looks like a small-hub prop meant for an outboard. I would start with a prop with the right size hub, somewhere in the 19 pitch range and go from there. Also, it shouldn't be a problem running that engine up to 4500 rpm. Mine was turning a 21p stainless faster than that.