Hub size

rphillips

Seaman Apprentice
Joined
May 18, 2012
Messages
46
Fooling with my 18' bass boat /w mercury black max XR2 150 hp. owned it appx.17yr. It came with a Quicksilver 3 blade 23p prop, & there was appx. 3/16" space between outer wall of prop & inner wall of lower unit. I just figured that's how it should be. Appx. 12 yr. ago, I traded for a 4 blade 24p from a prop shop, no name on it, but it helped the holeshot, didn't fix but helped, same gap. Today a buddy loaned me 2 of his props,( I'm still trying to get a better hole shot ), to try. I put his on there & that gap closed to maybe 1/16". Have I had the wrong size all the time? What sizes do they make? where do you measure the hub dia.? inside, outside, outside of lip that goes up in lower unit? How much difference could be expected from my smaller hub & the larger hub, pitch & diameter being the same?
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,033
Merc used two different size hubs on their larger motors. The inline 4/6 cylinder motors used a 4-1/4" hub, as did some of the early V6 motors. Most of the newer (90's and newer) V6 Mercs were 4-3/4" hubs.

The prop hub should fit inside the gearcase lip, with less than 1/8" clearance.

Two comments, I tried the smaller hub inline 6 prop in my V6 Merc and all I got was a lot of ventilation. She did plane, but the slippage was high, so I am surprised your motor worked as well.

Secondly, a 23" pitch prop is usually too much for your boat/motor combo. A 24" pitch prop would be worse.

You might provide some hub measurements and some prop numbers so we can figure out exactly what is going on.
 

rphillips

Seaman Apprentice
Joined
May 18, 2012
Messages
46
when I bought this outfit, it had a small hub Quicksilver 3 blade 23p, no idea of dia. on a 1985 XR2 150 eng. I found this small hub 4 blade 13 1/4 X 24P, at a prop shop, no name or #'s on it, shop said it was 24P, that gave me a little better shot. Yesterday I tried a small hub High five 12 3/4 X 24P, gained appx 300rpm, lost a few sec. hole shot & appx 3 mph. on top Tried a big hub Mirage 21P, lost a lot on hole shot, eng. just strained & moaned a lot before getting on top of water lost appx.4 mph. on top I had a big hub Lazer II 23P with me, but didn't have the correct bushings & washers to get it mounted to my eng, The small hubs 4" OD of the little lip that goes up in the lower unit housing, & the bigger ones are 4 1/2". Will try 23P Lazer II another day.Ventilation makes sense why I get by with the 24P, & the Mirage 21P, with no ventilation couldn't slip so strain & moan till it gets going. May try to find a 19P or 21P big hub of some sort to try. Hoping for something good. All ideas appreciated, Thanks, Rick
 

rphillips

Seaman Apprentice
Joined
May 18, 2012
Messages
46
I've been researching props a couple of weeks now, looked & read about bunches & bunches of them. I never see the hub size listed anywhere, WHY????
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
The V6s used the 4 3/4 hub right from the get go. In the late 80s and 90s some of the XR series got the smaller 4 1/4 props.

rphillips... Hub size was rarely mentioned as the props were known as Inline 6 or V6 props. Incidentally, the V6 when introduced, it was decided to use the same size prop as was being used on the MerCrusier Sterndrive
 
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