prop carrosion

tboat

hey guys, any ideas why my stainless steel props are corroding. the boat was in the water about two months but it was fresh water. thought stainless was stainless

elarson5757

tboat said:

thanks. that might be why it was hard to keep straight at no wake speed.

Although it may be making it worse..the B3 is known for the slow speed constant back and forth wander.  Mine is gone after adding trim tabs and I put them all the way down at slow no wake speeds...

Without them it was constant back and forth steering to keep it straight...

Handymans342

Did you clean them first? Can you post a photo?

Black_Diamond

I bet it is more cavitation damage than corrosion. Really hard to corrode the SS props when next to an AL drive. 

Handymans342

What causes that cavitation? 

Handymans342

Are they B2s? B3s? Volvo? Maybe the zinc was not installed???

Black_Diamond

Stainless steel is really a misnomer. Dependinging on the actual grade, i.e. 302, 304, 316, 440C, PH series... all have their own issues with oxidation and corrosion. The 'stainless' is due to the chromium oxidizing on the surface and effectively sealing the base material from the elements.  Bad moves are for example drilling a hole in stainless with a steel drill bit and not passivating it afterwards. Thus why you hear to never use a steel wire brush to clean your props. You will leave iron partials behind and will cause corrosion. 

My my metallurgical seminar for the day.  lol

Michael T

....all stainless means is "less" staining/corrosion than lower grade steel. Cavitation can be caused by trimming too high but you should feel the prop slippage at that point.

Are your engines operating in their proper wide open throttle (wot) range.  If not, it could be due to prop misalignment, poor hubs, etc. which could cause cavitation (bubbles along the prop blade surfaces) which can quickly erode the props.

LaRea

Corrosion, or scaling?  

Scaling is a thin, rough coating that typically develops on freshwater SS props from the combination of anodes and a Mercathode system.  You can remove it with mechanical action (sanding) or (some say) a strong scale remover such as Lime-Away (which has never worked for me).

Corrosion would only happen if something is badly wrong with your corrosion protection system.

Handymans342

Handymans342 said:

What causes that cavitation? 

raybo3

Handymans342 said:

Handymans342 said:

What causes that cavitation? 

Handy IMO a few things can cause cavitation. Trimming the outdrive too far up. Something (like fishing line) wrapped around the prop. Barnicals and growth even a bent prop can cause it.

tboat

B3s mercury with some damage (there stuff under that water) the anodes look good. I took them off and plan on getting them repaired is it possible to put them on the wrong way, all the splines look the same

Handymans342

They dont look lined up.

Thanks Raybo

Black_Diamond

You cannot (well reasonably lol) put them on 'wrong'.  However, they need to be clocked properly and your are not.  If the front (towards bow) prop has a blade at 12 o'clock, the aft blade should be clocked so it has a blade at or near 6 o'clock.  The blades should NOT line up like yours.  This can very well cause the cavitation and poor performance.

A quality prop shop should be able to weld repair and tune the blades.  Look for someone near you with a Prop Scan device.

Also, when you put the blades on, make sure you use the Mercury 2-4-C grease on the splines!

Black_Diamond

BTW: If you pour The Works toilet bowl cleaner (not the think stuff) on the blades and rinse they will clean right up from the scale.  Don't use a wire brush.  They are not polished props so do not expect the mirror finish.

frenchship

Paul

tboat

thanks. that might be why it was hard to keep straight at no wake speed.

Cableguy Greg

A mixture of muriatic acid and water will shine them right up.

randy56

Miss align  props do not cause low speed wobble. You probly have some ware in the transom housing,  However props should be as in frenchships picture

Michael T

....like I asked...are they aligned correctly? No.

06Rinker270

Photo is a bad angle but you can see the top 3.  I used prop speed.  Works great until you hit sand and washes the edges away and then you get growth and spend hours cleaning them off and then it grows back and then you clean it off and grows back and on and on and on. I love boating.