Prop ID: Merc 470

[nola mike]

just got a "new" outdrive to replace the one that i should have checked gear oil in sooner...
as a bonus, it came with a quicksilver SS prop. both drives are from merc 470's, my original is a 170 with a QS alum prop. old prop turned 4600 rpm @ WOT.
i've been unable to find out the sizes of these props from the numbers stamped on them:
aluminum: 1920P23
SS: 48 739x(i think?)0 a5 19p. presumably this is a 19p prop--is the other a 23p?
follow up question would be whether these props are comparable (ie, SS v. aluminum), or if i just need to take it on the water and see.

 

[Bondo]

Re: Prop ID: Merc 470

Ayuh,... If you were turning the right rpms with the 19",...
It's gonna be a Dog, lugging to beat 'ell with the 23" prop... I doubt you've got the HP to turn it..

 

[nola mike]

Re: Prop ID: Merc 470

so...is one of these a 19p, and one a 23p?

if anything, it looks like the stainless is a 19p, which should make the boat over-rev.

and i guess you're saying that stainless v. aluminum shouldn't matter as far as rpm, and that the pitch is all that matters? i didn't know if aluminum might have more slip, necessitating a lower pitch in SS to turn the same rpm.

 

[hwsiii]

Re: Prop ID: Merc 470

Mike, there is normally a great deal of difference in blade geometry between aluminum and stainless props. Usually you would go down in pitch some when you get a stainless prop, but a change of 4 inches is normally much more than I would recommend. Bond-o was just saying that if you were turning the correct RPM with the 19" stainless that he thought the 23" aluminum would not reach the correct RPM and Lug the engine.
You say the Quick Silver Aluminum was turning 4,600 RPM, and with the 19" stainless prop mounted on the boat I agree with you that it will be over revving a lot.
Theoretically speaking, changing from a 23" pitch prop from the same manufacturer and model to a 19" would gain about 970 RPM. So I believe that even though you are changing to a stainless prop you will probably be turning over 700 RPM more than you are currently turning with the 23" aluminum.


H

 

[Bondo]

Re: Prop ID: Merc 470

and that the pitch is all that matters?

Ayuh,... Basically, Yes...

 

[nola mike]

Re: Prop ID: Merc 470

thanks for the replies guys...although no one has answered the question of what sizes/pitches these props actually are...i was just guessing

might as well give the SS a try in the spring, and see where we end up.

 

[Bondo]

Re: Prop ID: Merc 470

although no one has answered the question of what sizes/pitches these props actually are...
presumably this is a 19p prop--is the other a 23p?

Ayuh,... We've Both replied/ implied that,... Yes, you're presuming correctly...


If I remember right, You've got outdrive gear Ratio/ID issues....
The 19" would be about Right, If you had the right gear ratio...
That explains the cheaper aluminum prop to sell the boat with the Wrong outdrive...
Putting that 19" on your boat, It could pull the arms right Off a skier...
It'll also Rev to the Moon if you let it go...
It'll be Waaaay under proped...

 

[nola mike]

Re: Prop ID: Merc 470

Ayuh,... We've Both replied/ implied that,... Yes, you're presuming correctly...

good.

If I remember right, You've got outdrive gear Ratio/ID issues....
The 19" would be about Right, If you had the right gear ratio...
That explains the cheaper aluminum prop to sell the boat with the Wrong outdrive...

i have gear ratio issues? the boat came with the original (AFAIK) outdrive...1.84 on a merc 170--that's the one with an alum prop. it does now have a blown upper gearset, which is why i bought outdrive #2. also from a 470, though i'm not sure exact model. also 1.84 ratio, if you believe the stamping on the side. this is the one that came with the SS prop. maybe you're thinking of another poster? or i'm missing something?

 

[ErieRon]

Re: Prop ID: Merc 470

My 1984 470 had a 1.84 ratio and came with a 14" X 19p prop. It's on a 23' cuddy, 3800 lbs, WOT 3800-4200.

Diameter is easy to determine...just measure from the center of the hub to the tip of a blade, and double that dimension. Pitch...not so much..

I'll check your Al prop number against mine when I get in to work and post back what I find.

Hope this helps.

 

[Fun Times]

Re: Prop ID: Merc 470

just got a "new" outdrive to replace the one that i should have checked gear oil in sooner...
as a bonus, it came with a quicksilver SS prop. both drives are from merc 470's, my original is a 170 with a QS alum prop. old prop turned 4600 rpm @ WOT.
i've been unable to find out the sizes of these props from the numbers stamped on them:
aluminum: 1920P23
SS: 48 739x(i think?)0 a5 19p. presumably this is a 19p prop--is the other a 23p? YES the 23p is the pitch for that aluminum prop, And the 19p is the pitch for the SS prop.
follow up question would be whether these props are comparable (ie, SS v. aluminum), or if i just need to take it on the water and see.

Here is the part number history of this prop starting with number 8 being the oldest one, The number has Superseded over the years.

Item Supersession Chain:
Row Class Part Number SS Level Disp Description
1 48 16316A46 00 ACT VENG 14R19

2 48 16316A45 01 SS VEN 14.00X19 RH

3 48 16316A4 02 SS VEN 14.00 X 19 RH

4 48 16316A5 03 SS PROPELLER

5 48 73980A5 04 SS PROPELLER I think this is what you're 19p SS is from mercruiser, from the number you posted this is what i could find after looking up some props for you.
6 48 73980A4 05 SS PROPELLER

7 48 88440A4 06 SS PROPELLER

8 48 74266A4 07 SS PROPELLER

And here is the price and the Availability of the prop if you wanted to buy a one new today from a mercruiser dealer, And if the dealer was out of stock and had to order it from the warehouse this is where it would be coming from.

73980A5 is Superseded to 16316A46
Class:48
Supersession Item Number: 16316A46
Status: Active
Weight: 13.813 lbs
Description: VENGEANCE 14R19
Package Quantity: 1
MSRP: $504.39
Price
Warehouse Quantity:
003 - FOND DU LAC,WI, Has Over 10 in stock
073 - ATLANTA,GA, Has only 6 in stock.
075 - FRESNO,CA, Has only 4 in stock.

And here is a link to show you the style, And name of the prop I believe you have from mercruiser. http://sites.mercurymarine.com/portal/page?_pageid=126,52105,126_52121&_dad=portal&_schema=PORTAL

Also with the number you posted with the aluminum prop, I could not find any info from it from mercruiser.

 

[nola mike]

Re: Prop ID: Merc 470

Thanks! Yeah, what I thought was an "x" on that ss was probably a rubbed-out "8". Looking through the owner's manual, the po (for the alum prop) circled prop part # 48-78124a4, corrosponding to a 13.5 x 23. I guess the smaller diameter might offset the larger pitch?

 

[Bondo]

Re: Prop ID: Merc 470

I guess the smaller diameter might offset the larger pitch?

Ayuh,... Generally speakin',...
The diameter goes in the opposite direction of the pitch when changes are made....
Also,...
Forget about Diameter,... It's out of your control, it's determined by the Engineer who designed it,...
Buy your props by Pitch...

 

[nola mike]

Re: Prop ID: Merc 470

Forget about Diameter,... It's out of your control, it's determined by the Engineer who designed it,...
Buy your props by Pitch...

not sure i understand this...i have to buy by pitch and diameter. in my user's manual there's a range of props for this outdrive, and both numbers vary--doesn't look like there's a "standard" diameter for alpha's. or am i off?

 

[Bondo]

Re: Prop ID: Merc 470

or am i off?

Yep,......

If you're going to buy a prop,....
Look up the listings for props that fit your unit, the Merc.s, Alpha 1, or whatever...
Then you pick the Pitch,+ the blade style you think you want....
Whatever diameter it happens to be,.... So be it....

You shop for Pitch that fits your unit,.... The Diameter isn't really a Choice....