Brass, bronze,nibral vs steel

[Florida Inboards]

Ok,
I have been asked this question by a customer and thought I would bring this topic up since all the old refrence from the old site is gone. Here Go's.

Why steel under water gear is prefered in high speed craft vs quality Nibral or brass componetry? What grade steel is being used to fab these underwater gear componets? And why not stainless steel? hopefully Art will tolerate my dumb questiions and help with this as we are restoring a number of older V-drives in the upcoming months, mild to wild.

Thanks ahead of time and please be kind!

Jody
Florida Inboards Inc.

[RiverRacer]

Simple, bronze just don't have the strenght of steel, and if bronze bends/flex it don't return, under power a bronze prop will flatten out then break!. You can use chrome moly or stainless(17-4)and heat treat, just got new strut and fins out of 17-4!...

BTW, the only dumb question is the one you don't ask!..:D

[lebel409]

Some of the Silicone/Bornze alloys have strength which approaches SS. However most steel/stainless steel components are welded then heat treated to deal with brittleness. Bronze components are cast. Strong in compression, weak with flexing. Once bent it cracks on return. Once cast it's done. Heat treating only softens it.

Bronze is used in lower HP applications. Works great in Saltwater. Excellent abrasion resistance, self lubricating. Alot going for it as long as you can survive the boat going over.

[Florida Inboards]

Thanks for the reasons and explanation.
we are starting to get into the 400 plus hp range in these tournament boats, and I think it may be time to start thinking down the stainless steel underwater gear road for some of these boats. I have been asked to build a 600 hp SKI FLY boat. keep in mind that this boat is a direct drive. it wont go more than 65 mph but getting their is right rapid.

Thanks again for the input I am going Steel ASAP on my old flattie.

Jody

[RiverRacer]

With 600hp you'll also have the torque and that's the culprit on hardware, and with that kind of acceleration you'll be flingin ears of a bronze prop in real short order!..

[gfinishline]

Way back in time, Ski Centurian had stainless underwater hardware. Rick Lee had Waynes Welding and us do his stainless struts, fins, ski tows and some rudders. So it's not a "new idea", in your field. "600HP" should have a strong strut brace too! I would not rig a 600HP boat with a SINGLE STEERING CABLE, nor any hardware that was not "thru bolted with nyloc nuts". Try a new strut on one of those "600HP" boats. Lower the shaft angle 1 degree (pull the prop up to the hull bottom) and see just how much speed you gain.

[Florida Inboards]

Most of the newer ski boats have very robust and beefy struts and rudders. not like the early 90's back. Also most of the ski boats are runnin 1.25" double taper shafts. Master Craft even runs a splined shaft. These boats have come a long way from the day's of Dads ole inboard. I do use Stainless Props for the real high HP application even though we have not thrown any blades on props in a long time. In years back a couple of the prop company's produced some products that had thin blates at the root, these had problems.
As far as shaft angle the Nautiques are the flattest at 13.5 Degrees most every one else run around 14.5 to 15. The Nautiques atain this flatter angle even though they have a down angle transmission.
Because I can not figure out how to post pictures on this forum I will post some on the photo feature of the under water gear that is pretty cool on my 07 Ski Nautique. I will also post photos of the real meat and potatos,, Dad's ole inboard that we have had since 1965. (it is a V-drive)!