Underwater hardware and corrosion

jklein · Posted: Jun 11, 2004 9:54 am Post subject: Underwater hardware and corrosion

For anyone who has mounted underwater hardware here's a question:

I've got a bronze scoop to mount to the bottom of my boat for a ballast raw water inlet / outlet. What type of screws should I use?

Brass / Bronze / Stainless Steel? Did you use wood screws?

tryan · Soul Rider Joined: 06 Feb 2003 Posts: 257

countersunk head stainless steel bolts with nylon lock nuts.

deepcove · Soul Rider Joined: 15 Mar 2004 Posts: 296 City: Vancouver

Any hardware you mount on your boat above or below the water line should be stainless.

MrBlean · Posted: Jun 11, 2004 1:45 pm Post subject:

DiyGuy · Soul Rider Joined: 26 Dec 2003 Posts: 460

What about the prop shaft and likely the majority of the props.

Hint - Stainless

colefooter · Posted: Jun 11, 2004 5:16 pm Post subject:

Use all stainless steel for anything frequently in the water.

MrBlean · Posted: Jun 11, 2004 10:29 pm Post subject:

DiyGuy · Soul Rider Joined: 26 Dec 2003 Posts: 460

Stainless and water:

Swim Platform mounting arms and bolts, exhaust pipes and hardware, cleats, grab rails, towers, nuts/bolts, deck screws, eye hooks, throttle / shift cable, steering assembly, clamps, and more.

I/O's - prop shaft, lock nut, cotter pin, vast majority of props (alternate - aluminum), hydraulic tilt pistons, lower unit bolts, Water intake screen, outdrive water pump parts, hi pressure braided hydraulic lines and fittings, swim ladders, ski hook, gas caps, brightwork trim.

Outboards - mostly aluminum except prop shafts, props, shear pins (dont see to many bass boats with aluminum props), brightwork rails, hinges, screws, nuts and bolts.

The only thing I can think of on my inboard that is brass is the water intake valve, rudder, transom drain plug, shaft packing nut, and port side engine drain plug and maybe a few other minor items here and there.

I don't disagree that brass is nice and maybe even preferable and is seen on a lot of cabin cruisers, classic sailing vessles, some marine application stuff associated and used in salt water. Cost would be a factor as brass is simply far more expensive and not as strong as stainless, Yes?

MrBlean · Posted: Jun 12, 2004 8:18 am Post subject: Brass v stainless

DiyGuy
Can't disagree with anything in your list. Now see why you say most props are stainless (and some ally) as you seem to be thinking I/O. I'm thinking tournament boat where most were definitely brass until recently.

Brass also oxidises so anything to remain bright should be stainless. Moreover, as you say, stainless has a higher tensile strength so anywhere where high torque fixing is required is best done with stainless.

However, we're talking a brass part here to be secured underwater through glassfibre. The bolts won't be under huge tension so there's no excessive strength requirement. Once the sealant used has cured the bolts are largely redundant anyway.

P'raps we should put it this way:

If you need to torque it up real tight, use stainless. If you just need to secure it and brass bolts are available to you, brass will be fine.

Is that a reasonable compromise?