a few aluminum prop questions

[Ripfence]

My boat has a three blade stainless steel 21p Mercury Laser II prop on a 19.5' Nitro powered by an 2006 optimax 150hp outboard. My wot is around 5,400 which is a little lower than it should be.

Anyway, I can run around 55-57mph with my current setup but I seldom ever do, I would like to trade top end for faster hole shot and staying on plane better at lower speeds. To do this I have decided that a four blade prop at 19p would do the trick. I would have tried trim tabs but the Nitro factory service tech said that due to the hull shape and swim platforms that they don't recommend trim tabs on this model. Going on the assumption that he right it looks like a prop is my only real choice, that being the case a $150 aluminum prop is more desireable than a $400 stainless.

My questions:

Can I get the desired results with a aluminum prop rather than stainless?

Some bass fisherman use aluminum props with the thought, "If I hit a rock then the aluminum will distort, taking the shock and preserve my lower unit" is there any truth to this theory?

Will the flex that aluminum has counteract the effects I am trying to achieve?

Are most aluminum props created equal or are there some aluminum props that are much better than others?

Are stainless steel props so much better than aluminum that I would be foolish to use anything other than steel?

 

[WillyBWright]

Re: a few aluminum prop questions

Most aluminum props are general purpose props. They work. But they're not specially tuned for performance. Stainless are much more specialized and the thinner blades slice thru the water easier. There are specialized aluminum props to be sure. Shop around. But stainless will always out-perform aluminum.

I've seen stainless props with minimal damage and the gears trashed. I've seen aluminum props with complete blades sheared off with far less damage to the gears. The better solution for that is composites, but they're not rebuildable. Although some have replacement blades. I find that stainless is best for performance. Composites next. General purpose aluminums last.

 

[walleyehed]

Re: a few aluminum prop questions

It's funny you mention composites, willy...I stuck a 4-bld, 18P comprop on the other day, and about 5 minutes into the run, I felt a slight vibration start, and just as I looked back, it shot a chunk (blade) about 20ft in the air and maybe 50ft to the right...faster than I could pull the power back, I was looking at almost 7000RPM. I shut it down and tilted up and there was nothing but a washer and a nut on the prop-shaft.....the entire prop shelled.
I'm not sure how they reinforce the splines, but everything was GONE!
I just installed this prop...matter of fact, I didn't even un-box it until I was at the ramp....clear, deep water all the way. About 5600 when she went...not even close to WOT yet......
Hell of a good hole-shot prop while it lasted.
I'm supposed to be getting a call back from comprop on this, but haven't heard anything yet.

 

[Texasmark]

Re: a few aluminum prop questions

I just bought a Hustler aluminum from here. Might want to check them out. They are what they say in the ad and seem to be a viable alternative to SS. I have been running high performance SS and was having a "clutch dog rattle" noise that I attempted to eliminate with the aluminum. It pretty much got rid of it, but I misguessed the prop I needed and pulled my rpm's down way too far. The Hustler had a better bite than I expected.

They have a removable hub that allows you to replace the shell if you ding it up and not the hub.....but if you really smack something you can take out the hub too.

They are very reasonably priced.

HTH

Mark

 

[Texasmark]

Re: a few aluminum prop questions

Something else. I hear a lot about aluminumblade bending. Well maybe so, but having spent half a century around aluminum I know that it work hardens, especially cast aluminum (which is what the props are made of) and if propeller blades distorted much from torque, they would surely work harden (over time), become brittle as a result ,and at the point of flex they would shear and fall off the hub.

So personally I'm not too worried about bending alum blades from engine torque. Yeah I know that when you hit something you can bend an ear on your prop and it not break off (necessarily); but that's not constant flexing. That is a single event.

Mark

 

[walleyehed]

Re: a few aluminum prop questions

I've got a couple of Hustlers, Mark, and I agree, they are darn good props.....I've run into a snag with some SS props I'm testing, and found the Hustler actually out-performed one of them......can't say which one though, not yet anyway...........8)

 

[Ripfence]

Re: a few aluminum prop questions

So it sounds like an aluminum prop might do it for me then?