Stainless vs. Iron Props

[farmo83]

A friend of the family has an Iron prop on hi 1100 TT day cruiser(made back in the early 80's). I asked why he didn't put a stainless prop on and he said it was to rigid and could break a blade as it wouldn't flex enough. Does this sounds right ? I'm pretty sure all I/O props are stainless and most of the drag boat props are as well.

[Racey]

A friend of the family has an Iron prop on hi 1100 TT day cruiser(made back in the early 80's). I asked why he didn't put a stainless prop on and he said it was to rigid and could break a blade as it wouldn't flex enough. Does this sounds right ? I'm pretty sure all I/O props are stainless and most of the drag boat props are as well.

1. They are not Iron they are usually Chromo 4340, or another hi-strength steel alloy, Iron and Steel are not interchangeable words, but we still understand the point of your post.

2. Stainless is brittle and work hardens, it forms cracks and is known to fling blades (just ask me, we've had alot of stainless props break, we've stopped using them altogether, cruisers get NiBrAl now, and runners get Steel) Menkens has done something with the way their stainless props are mfg'd over the last 7 or 8 years, and they are pieces of junk IMO now, they used to be pretty awesome, Lee at schiada has had the same problems as us with them, he doesn't recommend them anymore either, even on cruisers. We had one fling a blade and cause a good $5k in damage, brand new prop, maybe had a total of 10 or 15 hours on it, and it was all easy hours (mostly 45mph, and the occasional 75mph run)

3. I/O props are Underdriven (so when your engine is turning 6000 rpm the prop on a 1.36 ratio (just about the highest I/O ratio) is only turning 4,400rpm). V-drive props are Overdriven, and on an 1100hp deal it's probably close to 50% overdrive, 6,000rpm engine speed means 9,000 rpm prop speed. Waaaayyy more stress

4. I don't know anything about what most drag boats are running for props, but i'd guess alot of them are running steel and not stainless... in fact there is a guy here in vegas that cnc machines props for drag boats, and they are all made from 4340 chro-mo forged barstock, not stainless.

[SGettmann]

1. They are not Iron they are usually Chromo 4340, or another hi-strength steel alloy, Iron and Steel are not interchangeable words, but we still understand the point of your post.

2. Stainless is brittle and work hardens, it forms cracks and is known to fling blades (just ask me, we've had alot of stainless props break, we've stopped using them altogether, cruisers get NiBrAl now, and runners get Steel) Menkens has done something with the way their stainless props are mfg'd over the last 7 or 8 years, and they are pieces of junk IMO now, they used to be pretty awesome, Lee at schiada has had the same problems as us with them, he doesn't recommend them anymore either, even on cruisers. We had one fling a blade and cause a good $5k in damage, brand new prop, maybe had a total of 10 or 15 hours on it, and it was all easy hours (mostly 45mph, and the occasional 75mph run)

3. I/O props are Underdriven (so when your engine is turning 6000 rpm the prop on a 1.36 ratio (just about the highest I/O ratio) is only turning 4,400rpm). V-drive props are Overdriven, and on an 1100hp deal it's probably close to 50% overdrive, 6,000rpm engine speed means 9,000 rpm prop speed. Waaaayyy more stress

4. I don't know anything about what most drag boats are running for props, but i'd guess alot of them are running steel and not stainless... in fact there is a guy here in vegas that cnc machines props for drag boats, and they are all made from 4340 chro-mo forged barstock, not stainless.


Racey - this is quite informative. I currently have a Menkens for my 21'. I had it magged and had been using it, but the idea of pitching a blade and making a mess out of things turns my stomache - (much like having too thick of a spacer between the tranny and motor). Who are you going to for the NiBrAl props?
Sean

[Racey]

Federal Propeller/Michigan Wheel...... Through Diversified Products.

[vdcruiser]

Racey, when you say "cruisers get NiBrAl" , You don't mean fast cruisers do you ? Sorry to say , I've experienced the "tossed blade" problem with stainless props too, twice! I use steel now.