shaft material information sought

Hi guys, I am new to the forum, first post, I am seeking information on the shaft materials that might have been used in a 1991 Grande Banks 36 Classic, twin engines, Lehmans Sabre 135, Borg Warner gear box.

It has a four blade prop, but I need to find out what material the shaft might have been made of? and the prop too, unless thats a 'how longs a piece of string question'?

Chrissie

Calypso Black Pearl said:

Hi guys, I am new to the forum, first post, I am seeking information on the shaft materials that might have been used in a 1991 Grande Banks 36 Classic, twin engines, Lehmans Sabre 135, Borg Warner gear box.

It has a four blade prop, but I need to find out what material the shaft might have been made of? and the prop too, unless thats a 'how longs a piece of string question'?

Chrissie

Click to expand...

Umm only guessing but I would assume from most boats that the shaft would be stainless steel and the prop would be brass.

Before you buy new, see if the old shaft and prop can be repaired.

Kinda like Hendo above, my gut says stainless steel shaft and bronze prop.

My 225 hp gasser is so equipped. 1 inch is my shaft diameter.

The choices of shaft material available I guess are;

Aqualoy 22
Aqualoy 19
Aqualoy 17
Monal 400
Monal K500
Tobin Bronze
or Stainless steel 304,

but I dont know which it is most likely to be?

The prop is either bronze or Nibral. Nibral is Nickel brass aluminum a bronze alloy that is significantly stronger and more expensive than bronze. Typically Nibral is 20 to 30% more money than bronze. It has strength close to but just shy of stainless, You will rarely if ever find a stainless prop on a trawler or for that matter any straight inboard. The only exception I have seen to that are tournament ski boats. There the strength of stainless is used to thin the blades from what a Nibral prop would need in order to gain a bit of extra performance. So if your prop is tarnished brass or bronze color, what is it made of? If it is Nibral, it is probably stamped as such. If not it is probably bronze. If your shafts are bronze they will be Bronze (yellow) color. If they are silver (white) there is almost no way to determine if they are 304, 316, or one of the Aquamet or Monel alloys (both are 'stainless' alloys) without material lab analysis. The good news is it really doesn't matter unless you are buying or making new. There are differences in strength and corrosion resistance between the stainless grades. Aquamet and Monel compare favorably to each other but are different trade names of different companies. Costs vary significantly between stainless alloys mainly due to varying chrome content. All shafts can be straightened within limits, and even worn under size diameters can be brought back to original size. Nothing is cheap but compare before replacing. Shaft work need not be done by a 'marine' shop. Many good industrial machine shops can do this work as well. As they would do for industrial equipment repair. Hope that helps.

GB used stainless shafts and bronze props. A GB 36 uses 1-1/2" diameter shafts. Stock prop on a GB36 was 3 blades. However many, like ours, have been fitted with four blades by their owners or previous owners.

Our 1986 GB42 has stainless shafts (however, they are 2-inch diameter). The original props were four blade bronze. We currently have three blade props.

Ray