Variable pitch prop

Status
Not open for further replies.

TRAILN

Petty Officer 2nd Class
Joined
Jul 28, 2011
Messages
121
Just a curious question. Why don't they make a variable pitch prop? Variable props on airplanes have been used for years. It just seems so logical :confused:
 

craze1cars

Lieutenant Commander
Joined
Dec 26, 2004
Messages
1,822
Re: Variable pitch prop

Google: Land and Sea Torque Shift

Read away to your heart's content. That was the most viable attempt at producing one. Depending on who you talk to, it generally worked well. The company either folded or discontinued it...not sure who owns the patent or if there even was one.

For that matter, why make a shifting prop when one of the big manufacturers could take the world by storm by offering a shifting gearcase...or better yet a CVT gearcase?

Why hasn't anyone taken one of these concepts and figured it out with today's modern technology? Either in the prop or within the gearcase? I haven't the foggiest. High price, low demand, complex shifting mechanisms, lack of reliablity? All speculation on my part...
 

wellcraft19

Petty Officer 1st Class
Joined
Jun 21, 2011
Messages
201
Re: Variable pitch prop

They do. Not too uncommon on larger (work) boats with a straight shaft. Older (commercial) fishing vessels also had them, in some cases even without a transmission. Once you started the engine, the prop started turning (these were very slow rpm diesel or kerosene engines).

You can even buy propellers for "our" size boats with variable pitch (http://www.piranhapropellers.com/).
You keep the hub, just change the set of blades to a new pitch. Think they are made out of composite and there are many posts here about their benefits and potential drawbacks. Main "purpose" can be that it is easier/cheaper to replace in case you hit something, although these props might be "no better" than an aluminum prop, and you can possibly buy two alu props for the price of one composite.

All that said, have not tested. Read posts from those who have tried them (and are running them).
 

ccole4

Recruit
Joined
Aug 2, 2011
Messages
1
Re: Variable pitch prop

I just purchased a Quicksilver Power2 Prop on E-bay for $150.00. Absolutely amazed at the performance of this prop. Very easy to adjust. It makes my 3.7 liter Mercruiser launch like a V8. My particular prop starts at a 13p and shifts to a 19p. Today I pulled my wife up on a slalom ski without any issue. My boat is a 1987 21 foot Galaxy open Bow. Worth every penny that I paid for it and then some.
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: Variable pitch prop

I think the best shot at a "shiftable" outboard gearcase was the one Merc had but never really produced. It was on a motor called Duces High. On the hood were 4 cards, all 2s, 1 heart, 1 spade, 1 diamond and 1 club. 2 hundred hp, 2 props, 2 speed, 2 cool. It had a dual prop gearcase and at low speeds only 1 prop kicked in. As the rpm increased the second prop kicked in.
 

elkhunter338

Master Chief Petty Officer
Joined
Jun 27, 2009
Messages
818
Re: Variable pitch prop

Pro-pulse at western marine makes a manual adjust prop.
You have to take the prop off adjust then re install.
I have run for 6 yrs with a merc 140hp I/O
 

Lakeshadow

Petty Officer 1st Class
Joined
May 29, 2012
Messages
205
Re: Variable pitch prop

I just picked this one up. It's made by Lesnor-Maehr Marine Co. It's a OBM-1. Have not tried it. On a 13.5 foot wooden boat and a 33 pony Ski-Twin it seems I should be able to dial up the pitch and get some good speed out of the craft.


IMAG0411.jpg
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Variable pitch prop

Years ago a neighbor had on of those props He felt that an actual prop change was more effective but the adjustable prop was convenient.
Keep in mind when selecting a pitch that your motor needs to be able to rev freely within its rpm rating.
With a light load its' wot rpm needs to be near the maximum rating.
Its possible that you might be able to adjust it closer to the low end of the rpm range for the best speed.
But hole shot and load carrying will suffer.Of course you can adjust it for best load setting.
The motor is rated for 4000-5000 rpm. HP is rated at 4500.
Raising the motor on the transom can add a couple of mph in ideal conditions. And of course
careful adjustment of the trim settings.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,030
Re: Variable pitch prop

I never thought the composite props were an answer. The pitch was adjustable, but had to be adjusted manually. Aluminum pros were stronger, and replacement parts for the composite props were too expensive, given their fragile nature.

I asked an old, grizzled Merc Dealer (now deceased) about the Merc Power2 props. It was his opinion that at $500 to purchase(expensive in those days, not so much now), and their chance to be damaged in normal useage, it just wasn't worth it to buy.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Variable pitch prop

In the very early outboards there was at least one that had a variable pitch setup controlled while the motor was in operation.
You could actually vary the pitch and go into reverse.
 

Centaur

Cadet
Joined
Oct 11, 2011
Messages
9
Re: Variable pitch prop

AeroStar Marine still make variable pitch props. They are not truly variable, rather they are two-speed props. They are a three-blade stainless prop that automatically shifts between high and low ratio depending on load. You select the high pitch to match the boat and the low pitch will be 6" less - e.g. a 21" prop will be 21" high and 15" low. There is an adjustment wheel on the hub that can be turned by hand (without tools) to adjust the sensitivity of the change point - at the extreme ends of the adjustment the prop will stay either in high or low!

The results are quite spectacular, launching a boat onto the plane like nothing else but the price is a little eye-watering. I had a Maxum 1900 SR3 fitted with a Mercruiser 4.3L MPI 220hp motor and Alpha drive. The standard 19" 4-blade Vensura prop would get the boat from 0-30mph in about 7.5 seconds. A 19" 5-blade High Five prop would knock half a second off that, at about 7.0 seconds but a 20" AeroStar would do it in 5.8 seconds, whilst hitting a higher top speed, running lower revs and getting about 0.5mpg better economy across the cruising range.

The obvious drawback is the cost but the blades were individually replaceable so repairs would be easy and, also, a spare set of blades takes up much less space on a small boat than a spare prop. The same could be achieved with a two-speed transmission and it seems odd that no-one makes one. Look through the prop section of the forum and there are no end of posts from owners who want more out of the hole performance but don't want to sacrifice top speed or fuel economy - simply not possible with a single fixed pitch prop. Whilst cost, again, would be an issue, surely this could at least be offset by being able to buy a more modestly powered boat. Most owners don't need absolute top speed and would be content with fast planing and good cruising economy - both achievable aims with the combination of a modestly sized motor and a two-speed / CVT transmission.
 

smokeonthewater

Fleet Admiral
Joined
Dec 3, 2009
Messages
9,838
Re: Variable pitch prop

One place I could see a variable pitch or shifting prop being huge would be a twin engine boat where one engine won't plane it with a standard prop but would with a much lower pitch.... if one failed you could limp home at 25 mph instead of 6 mph
 

Lakeshadow

Petty Officer 1st Class
Joined
May 29, 2012
Messages
205
Re: Variable pitch prop

Very cool centar. A variable "on the fly" prop would be way cool on the old timer, yet it seems something like this is unobtainable for '60's Evinrudes. Top speed with the mighty 15 pony was 21 on this Droid g.p.s. Steping up to 33 ponys and a mini jack plate this year. Manually adjusting pitch for canal crusing and top speeding.... Can't wait.
 

trainricky

Recruit
Joined
Jan 16, 2014
Messages
1
Re: Variable pitch prop

Just a curious question. Why don't they make a variable pitch prop? Variable props on airplanes have been used for years. It just seems so logical :confused:

they do! my dad had a baja boat. with a 4 cylinder i/o.... his friend had a boat with a v8...... so.. my dad is smart and he got a variable pitch prop, you change the pitch of the prop by adjusting the trim...... real cool..... no problems with it..... so the baja islander 180? late 1980's....... would pull tube, skiers, go about 50......why do they not have these anymore??? it was trouble free, and my dad's friend with the v8 only went 5 mph faster,,,,,, the baja had a small tank... the other one had a 70 or hundred gallon tank hehe..... i found this forum trying to show my friends wife how you can make a little do a lot..... now i look like an ***... i will find out the prop though..... we finally got a nice boat with v8 he didnt get the prop with it, i dunno why, because it seems it never happened,,,,, 89 88 87 86 good years!!! but now you know they made (make) variable pitch props changed by trim, to make the lil baja keep up with the v8!
 

jestor68

Commander
Joined
Jun 12, 2012
Messages
2,308
Re: Variable pitch prop

AeroStar Marine Corp makes one. All SS. Bring $2000. :facepalm:
 

1FASTLASER

Petty Officer 2nd Class
Joined
Dec 8, 2006
Messages
158
Re: Variable pitch prop

I think the best shot at a "shiftable" outboard gearcase was the one Merc had but never really produced. It was on a motor called Duces High. On the hood were 4 cards, all 2s, 1 heart, 1 spade, 1 diamond and 1 club. 2 hundred hp, 2 props, 2 speed, 2 cool. It had a dual prop gearcase and at low speeds only 1 prop kicked in. As the rpm increased the second prop kicked in.
I know of one of the Duece motors still in existence. High dollar and regrettably it was NOT a success. If Mother Merc dropped the idea it should have told people it was just not feasible for normal usage. One of the major problems with a transmission on a planing hull simply put was it's just plain dangerous. Imagine this if you will..... Your up and running on the pad and all of a sudden your rpms drop. What happens next is you drop off pad at speed and loose control. Not a pretty sight and it does tend to get smelly as you will prolly crap ur britches. The land n sea prop has had some success as it was a progressive change.... Not an abrupt change
 

dan t.

Lieutenant Junior Grade
Joined
Feb 28, 2008
Messages
1,131
Re: Variable pitch prop

Actualy the odd drag boat uses of all things the Gm Powerglide,I saw one a few years back, slick set up. They dont use a torque converter just a pump and input drive with a pump bypass system, very similar to what the IMCA oval track cars use. This was a shaft drive, start in low 1.76 ratio shift to high 1to1. I saw this thing run on a local lake, very scary.
 
Status
Not open for further replies.
Top