20H prop

[Tom Heintzberger]

Can any tell me what the diameter and pitch is on a stock Mercury 20H hydro propeller?

Thanx

[ZUL8TR]

20H prop

With 16:21 gears and toilet exhaust?
or
With 1:1 gears and standard H quicki tower?

As an example my 25ss early version 1973 with 16:21 uses a 7" x 13" pitch plus cup and runs at 7000 rpm with shaft CL at 3/4" below bottom. Speeds about 62 - 63mph

I have 3 props I use on it, one at 7" dia and 2 at 7.3" dia and all have about the same average 13" pitch at 2" radius, but all have different leading and trailing pitches for different progresssive pitch layou. No surprise they all run different with different setups.

[Tom Heintzberger]

I'm running 1:1 gears and Standard H tower.
The "Mercury Master Service Manual" has two part #s for 20H "B" hydro w/1:1 - bronze 48-21055 and SS 48-26011.
20H w/ 16:21 "B" H&U 48-29926
I have not found anything to tell me what the pitch and diameter was of these props.

[sam]

I'm running 1:1 gears and Standard H tower.
The "Mercury Master Service Manual" has two part #s for 20H "B" hydro w/1:1 - bronze 48-21055 and SS 48-26011.
20H w/ 16:21 "B" H&U 48-29926
I have not found anything to tell me what the pitch and diameter was of these props.

That is correct, they did not publish the exact specs.

The information you have been given is correct.

[BmJuby]

What about 1:1 with the conversion? Thoughts on pitch diameter, or is there not much difference between 1:1 converted and 1:1 unconverted?

[B1PRORACER]

This would do... if you could find one!

The props on a 20H conversion with a 1:1 gear ratio would use propellers that are the same as those for the MK30H "C" classes. For Unconverted 20H with 1:1 ratio, I believe that the stainless steel prop of choice is a 48-23636. Everyone in the 70's thru to the mid 80's was looking for these propellers as "blanks" for ASR propellers- the root pitch was better than the other B/C propellers. Probably a long course ASH or ASR propeller from the mid-80's on would be good... run it a 1/4" lower on the transom.

[sam]

A "B" Merc and "C" Merc would use the same prop?

Just seems a little unlikely when using the same ratio

[Guest]

20-H prop

If I remember correctly we ran a 6x7 on the A runabout and a 6x8.5 on the B runabout with 1:1 gears.
I will check my old prop box! I do remember running a 7x13 Michigan on the B runabout with gears and a 7x14 on the hydro set high.

Alan

[rumleyfips]

Who knew?

I remember being surprised by John Webster at Silver lake , New York in the late 70's. He ran the same boat in A & BSH but he also ran the same wheel. A 1-1 B could use a prop just over 6x9.

By the way, he ran well in both.

[B1PRORACER]

You are right Allen. At the end of the KG4H era- the ASRs were running 6X9 props with the previously mentioned prop as a blank (with the reduced root pitch). The ASH boats could pull a 6x9 1/4 prop- usually with the more common 48-26048 props as blanks. This was one of the few Kamic props that was very close either for the B or the C. I am going by memory on the prop numbers and I don't have my Mercury books handy to refer to. My brother was competitive in the mid-60s in CSH with the prop that won the 1962 nationals in BU. I still have that prop... and yes, it had a little too much diameter for a late 70s ASR.

[B1PRORACER]

A similarly amazing thing that I saw in the 70's.... Roger Hartwell ran the SAME two blade prop in 25ssR, 25ssH, BSH, BSR and SuperC!

Howard Pickerell and his friend Gibby Peterman used to trade props between ASH and PRO250ccH.

I won the nationals in 250ccH and 250ccR with the same propeller....!

My Nephew's best JSR (60J) propeller was right off a vintage KG4Q engine. The blades were think and the area was big. I never cared what a prop looked like or where it came from.... put it on and see what it does!

[G Stillwill]

I still have the prop that my Dad won the nats in ASH in 1962 and its a Smith wheel that was worked for a Merc Quincy A deflector Alky with 1-1 gears. All those props from Smith we had were worked brass Kamic KB- 6 and KB- 5's. Pop Smith used his own set of numbers when he stamped a prop so not sure what the pitch is but the Dia is 6 in. The one Hopkins I have is stamped 6x9 and is for ASH.

[Guest]

Props

We have been running a two blade 6 3/4 by 9 1/2 on our C MOD Merc with 1:1 gears with some success until the last race of the season. Guess it got a litttle tired!.

Alan

[David_L6]

We have been running a two blade 6 3/4 by 9 1/2 on our C MOD Merc with 1:1 gears with some success until the last race of the season. Guess it got a litttle tired!.

Alan

9 1/2 pitch sure sounds low to me for a C Mod Merc.... Must have been running it pretty deep???

[ricmontoya]

Props - 20H 1-1 non conversion

Here a couple of props, 1) is a6x9 Kamic, the other is a 6 3/8 x 10 1/2 Cary, $50 each.

Ric - 206-283-4773 ricstr4@gmail.com