Author Topic: I want a new prop please help decipher these numbers  (Read 1540 times)

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Offline vashtsdaytona

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I want a new prop please help decipher these numbers
« on: May 15, 2023, 11:33:11 PM »
These are pictures of my current alum prop.

I think I was a 3 blade 23 or  in stainless. My understanding based on calculators this should drop rpms about 350 relative to speed it is now.

135hp black max, cvx17.  It can easily get to 6000rpm and I can get an honest 60mph GPS.  I'm not really looking for more speed, I'd like to keep the same speed but bring down the rpms

Right/wrong?

Now also what diameter do I need.  The numbers make me think current is 12in and a very rough tape measure says 12in.  But now I'm thinking thats wrong, when googling this number I'm seeing 14.5in??m

My hope is to find good used one, but I'd be happy to take any links you have to whatever would be appropriate

« Last Edit: May 17, 2023, 07:29:34 AM by vashtsdaytona »

Offline Hyperacme

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Re: I want a new prop please help decipher these numbers
« Reply #1 on: May 16, 2023, 11:44:21 AM »
It's a Merc / Quicksilver 13.75 diameter 21 pitch
Will fit Merruiser and V6 outboard

Maybe try a 21 pitch stainless steel prop.

Offline vashtsdaytona

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Re: I want a new prop please help decipher these numbers
« Reply #2 on: May 16, 2023, 06:21:36 PM »
Thanks for reply, you recommend getting the same pitch but in stainless, would that make a difference?

Offline Hyperacme

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Re: I want a new prop please help decipher these numbers
« Reply #3 on: May 16, 2023, 06:54:30 PM »
OOPPPss .. fat fingered and didn't proof read ..   22P stainless.

Dane has same boat & motor as yours .. and should know best prop.
Was hoping he would see this .. maybe a day or two when he logs into forum

Offline aquamaniac

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Re: I want a new prop please help decipher these numbers
« Reply #4 on: May 18, 2023, 10:30:53 PM »
Sorry, I'm a little late to the party.

Your 48-78122A40 propeller is a 13 3/4 diameter 21" pitch alum prop. I'll attach a page from the 1991 Mercury propeller catalog. All of these props are probably out of production now but you might be able to find them used.

The 23" pitch QSS Stainless would be 48-16320A5

I do have a 1985 CVX-17 with the 135 Merc. First motor was a 1986 and I replaced it with a 1998 Merc 135. Performance was very close between the two motors with the 1998 being a little stronger especially out of the hole, and better starting and idling.

I generally run a 23" QSS unless I'm pulling strong slalom skiers and then I run 21" High Five. I also have the same Alum prop that you have and was happy with the performance of it.

These boats really respond to trim, and even with the 23" stainless prop I still hit 6000 rpm trimmed out.

Offline vashtsdaytona

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Re: I want a new prop please help decipher these numbers
« Reply #5 on: May 21, 2023, 12:16:45 AM »
thank your for that great information.

newb prop buyer question about compatibility

we are sure

48-16320A5

would fit my 88 black max 135?

perhaps props fit decades worth of motors?  I dont know those things.  In car or motorcycle world, usually a much more narrow range of interchange


Thinking that my current prop is on that chart and it fits, then any of those should also physically fit up?

I might have gotten excited and jumped the gun on what I thought was a good deal.  I bought a new old stock 48-16320A5 that happened to be on eBay at the moment.

Hope this link works,   https://www.ebay.com/itm/284819905742?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=Qr99WhKIQ-y&sssrc=2349624&ssuid=OOoNzKE1R1q&var=&widget_ver=artemis&media=COPY


So will that just swap right over?  I have
 Taken props off for service reasons but only put back what was there, not worried about the procedure, but would I need any other adapter or different spacers/hardware?   I am hoping it will be just easy off easy on


The hub on the stainless looks to be much deeper/recessed from the outer face, compared to my alum 21.  Which makes me worry about fitment
« Last Edit: May 21, 2023, 02:36:40 AM by vashtsdaytona »

Offline Hyperacme

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Re: I want a new prop please help decipher these numbers
« Reply #6 on: May 21, 2023, 02:20:54 PM »
That prop is on the chart to fit your motor.

Offline vashtsdaytona

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Re: I want a new prop please help decipher these numbers
« Reply #7 on: June 07, 2023, 04:00:43 PM »
Prop arrived as described in new old stock.  it was a direct fit and all is well.  gave up accel but gained in every other way, as was expected.  thank you for helping.