Prop hub numbers, what will they tell me?

ParallaxBill

Petty Officer 1st Class
Joined
Aug 27, 2006
Messages
341
Guys,
I just tested my 73 Glassmaster Tarpon w/165 Mercruiser in very good tune. But I am only getting 3,500 rpm @WOT in good trim 4 adults on board. Previous owner noticed the drop in rpms but thought the spark arrester being dirty was the problem. It has since been thoroughly cleaned. He also noted the rpm loss about the same time as his prop change to a higher pitch SS prop "duh".;)

So, what I have is a good running motor not turning the 3,900-4,100 rpms I think I should be getting. The only info I have on the prop is the hub numbers as follows. What can I learn from them?

On the hub face are...5, J then 48-73982-21.

Is it safe to assume the pitch is the last two digits? Also the prop is 14" in dia. if that much.

What do you recommend? I'm thinking a 19-20" pitch aluminum prop. No? The boat is heavy at nearly 1,800 Lbs, should I go for a 4 blade?
 

ParallaxBill

Petty Officer 1st Class
Joined
Aug 27, 2006
Messages
341
Re: Prop hub numbers, what will they tell me?

Found the answer I was looking for about the numbers. Just typed them into a google search and got this;

Stainless Steel Mercruiser prop, 13 & 3/4 X 21 , 21 inch pitch, Like new, Mercruiser part number 48-73982-21 $295.00
 
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