three blade or four?, aluminum or steel ?

[tywos]

I am about to buy a new prop. need some input please..<br />I have a 1966 (65hp) merc 650. The existing prop is a three bladed aluminum 14in. 15deg.<br />I heard that a steel, four bladed prop, would be much better?<br />Any suggestions? thanks<br />Ty.

 

[JB]

Re: three blade or four?, aluminum or steel ?

Any steel prop will cost more and take more abuse, Tywos. Usually they will improve both accelleration and top speed, but not a lot. Less drag than an AL prop.<br /><br />A 4 blade prop will improve hard accelleration and lower top speed (more bite, more drag). Also cost even more than the 3 blade steel.<br /><br />What are your priorities and what are you willing to pay for them?<br /><br />Good luck.

 

[Clams Canino]

Re: three blade or four?, aluminum or steel ?

To add to that, unless your priority is pull toys, three blades is sufficiant. SS is always a "good thing" if you can afford it.<br /><br />-W

 

[wilkin250r]

Re: three blade or four?, aluminum or steel ?

There is not one "perfect" type of prop, or we would all be using it. The prop you want depends on the performance you want. Like JB said, a 4-blade will improve acceleration, but decrease top speed, very good for pulling skiers where you need to pop up on plane very quickly. 3-blade will give you better top-end speed.

 

[tywos]

Re: three blade or four?, aluminum or steel ?

Great, thanks alot for the info.<br />will take it all into consideration (along with the price heh) when buying my new prop.

 

[BillP]

Re: three blade or four?, aluminum or steel ?

F1 racer winners are using 5 blade props and getting better hole shots and higher top end. The blades look like a standard prop with cleaver tip. They used 2 blade cleavers for years and years but not anymore. Things are evolving to smaller diameters with more blades.

 

[rickdb1boat]

Re: three blade or four?, aluminum or steel ?

I would have to think real hard about putting Stainless prop on a 1966 merc 650. I don't think you will gain all that much from it. You may want to try a lower pitch(13") and see what happens. Just my opinion, BTW, I had a 67' 650 and it was a great motor...

 

[ZmOz]

Re: three blade or four?, aluminum or steel ?

A 4 blade prop is like 4 wheel drive for your boat. I don't think I would use either a stainless or a 4 blade on a 65hp...

 

[tywos]

Re: three blade or four?, aluminum or steel ?

Okay, i have decided to go with an aluminum three (3) bladed prop.<br />Now what the owner before me had mounted on the eng. was a 14in. 15deg. prop.<br />i can't seem to find that combo for my motor...<br />And now i'm wondering if that was the right one installed in the first place?<br />I haven't installed a tach. yet, soo not sure on the R.P.M's at WOT...and there for not sure what Deg. i would need.<br />i was simply going to replace with what i had found on the boat when i bought it. Any suggestions?

 

[rickdb1boat]

Re: three blade or four?, aluminum or steel ?

tywos <br />The only sure way to know what prop you need is to add a tach and see what you're running at now. Do not be concerned about the degree of the blade right now. Just the pitch. Almost all props made now have some cupping in them anyway. The simplest Tach to get for your motor is a Tiny-Tach. Easy to install and works on ANY motor.<br /><br /> Tiny-Tach

 

[BF]

Re: three blade or four?, aluminum or steel ?

Hiya,<br /><br />I think you're probably right to stay with aluminum. An advantage of aluminum is that is softer, and if you hit something the prop will break (hopefully) before something more expensive in the lower unit does. Another advantage of aluminum is that it can easily be "re-conditioned" by a prop shop relatively inexpensively. Even badly dented props or props missing big hunks of the blades can be re-welded, re-ground & balanced to be put in "as good as new" condition. Of course they can be re-hubbed if need be too. A good prop shop will also be able to tweak the pitch a bit for you (up or down an inch) or add some cup if you want to change performance more subtley than going up or down a whole size in pitch. <br /><br />You don't say why you're buying a new prop. Are you trying to alter/improve the boat's performance? or has your current prop been damaged? Is having your old prop rebuilt out of the question for some reason? If you're looking to buy because then you'll have a spare (not a bad idea) maybe you wanna try a different pitch so that you can use one for skiiing and the other for cruising. Like has been said, whether you go up or down in pitch depends on where you are now (and rpm's help you know). But, if your boat's a real dog out of the hole, builds rev's slowly and has difficulty pulling a skier out of the water, chances are you don't want to go higher, in pitch! (you probably want to go lower). You might know that even if you don't have a tach.<br /><br />Hope that helps.<br /><br />Brent

 

[rickdb1boat]

Re: three blade or four?, aluminum or steel ?

What size and type of boat is this on anyway? Approximate weight of the boat?

 

[walleyehed]

Re: three blade or four?, aluminum or steel ?

An advantage of aluminum is that is softer, and if you hit something the prop will break (hopefully) before something more expensive in the lower unit does. Another advantage of aluminum is that it can easily be "re-conditioned" by a prop shop relatively inexpensively. Even badly dented props or props missing big hunks of the blades can be re-welded, re-ground & balanced to be put in "as good as new" condition.

This statement is true to some extent....It is also the reason I run ONLY SS props.<br />Having to repair aluminum every time you go out is not a problem you need to deal with UNLESS you are running in areas with good size rock or concrete. This would be the only situation in which aluminum is better than SS.<br />As long as you're not running a solid hub prop, the hub WILL spin 99.9% of the time with SS, and the stainless prop will pay for itself in a short period of time if you're hard on aluminum.<br />I've hit just about everything you could imagine with a Stainless prop, and I will promise you this...If you're at WOT and you hit Rock....with aluminum-new prop(and lower unit), with SS....install new hub, straighten blades and install on new lower unit.(I've tested this theory)

 

[andrewkafp]

Re: three blade or four?, aluminum or steel ?

One small advantage (Only cosmetic)is you NEVER have to paint or touch it up when it's SS, but with alloy, the paint never stays on.

 

[BillP]

Re: three blade or four?, aluminum or steel ?

In my humble opinion the ONLY good reason for using an aluminum prop is low price. Like posted above, rubber hubs and shear pins keep the gears from getting trashed. Aluminum props are good as a backup prop.

 

[rickdb1boat]

Re: three blade or four?, aluminum or steel ?

Stainless is fine, guys. But on a motor of his vintage and size, it may be overkill. Plus, it would probably costs more than the motor is worth. I'd still stay with the aluminum, unless he is looking for the absolute top performance he can pull out of it. At best, it's gonna be minimal with that small of an engine...

 

[tywos]

Re: three blade or four?, aluminum or steel ?

The boat is a 15ft. fiberglass V-shaped hull.(StarCraft)<br />not very heavy, i would have to assume. (have no idea what the actual wt. is)What i do know is that it takes awhile to plane up and on top of the water. Once i am on top, there is no problems...just takes awhile to plane up.<br />ohh.. and thx for the tiny tach link..plan on ordering one very soon...thinking i should buy tach, check RPM's, then buy a prop that would fit my needs (fishing, and ski'ing).

 

[walleyehed]

Re: three blade or four?, aluminum or steel ?

Rick, we run SS on both of our Fish and Game boats, 50hp 4-stroke Mercs, because we don't have time to replace a prop everytime you hit a twig or stick, and we DO run these 2 in the rocks as well. we're always shallow, in the thick of things, and it's nice to know "props" are not an issue when trying to get work done with these boats.<br />It's the most important link between the power and water, and I have to recommend SS even on this engine, because it will pay for itself in a short time.<br />There are many people out there running aluminum props that may have a ding as small as a pencil eraser, and have no idea what dynamic and static balance problems they have with that simple small ding, and it WILL show it's ugly face in time due to excessive side loads on the L/U at WOT, not to mention the static balance issue.<br />SS props just don't have the same issues in that area, and that's why I recommend them.