B3 Corrosion

[sailsmanship]

Looking at a 2001 boat with Bravo Three outdrive.The housings look in good condition except for an excessive amount of corrosion around the area of the propeller output shaft. It's real bad. Could this be galvanic corrosion between housing and props? Is this common ? Anybody know a rough cost on how much to fix. I know that it depends if there is any water intrusion. Lube looks good.

 

[Mischief Managed]

Re: B3 Corrosion

Yes it is indeed galvanic corrosion and it's probably due to poor maintainence. B3s require constant upkeep to stay on top of corrosion. <br /><br />You may not need to fix it if it's not leaking and you arrest the problem now. I have seen some horrid looking B3s that stall work fine. Mine had minor corrosion in that area but I have been diligent about corrosion prebvention and it is not getting any worse. <br /><br />To correct it, you should sand blast all the corrosion off the drive, prime with zinc cromate and repaint the drive. Supposedly Rustoleum gloss black is better thatn Mercruisre Phantom Black. I have yet to try it.<br /><br />If you don't have a sand blaster, it's a great excuse to buy one.

 

[DHPMARINE]

Re: B3 Corrosion

Is it the lower unit housing itself that you are looking at?If the prop(S) is off,and you are looking at the propshaft,it maybe an anode you are seeing.If so it is made to 'erode' and is replaceable.<br /><br />DHP

 

[sailsmanship]

Re: B3 Corrosion

The props are off. Corrosion is at the end of the housing right at the seal. About 4-5 inch in diameter

 

[TilliamWe]

Re: B3 Corrosion

Sandpaper, that is actually the rear bearing carrier. Believe it or not that piece unscrews from the housing. Mischief has seen pictures of my drive, a 1997. That carrier is corroded so bad, that I can actually see a little part of the edge of the seal! But it's been that way for 3 years now. Once I caught the problem, I have stopped it's progression. I repaint the drive every year, and I bought the "freshwater only" anodes off mercstuff.com. What caused my problem was that my dad (the original owner of the boat) put in a battery switch & a second battery. Well, I was turning the switch to "OFF" and was turning off my Mercathode system. So for two summers, my boat sat in the Illinois River, at a 30 year old marina with rusting docks, getting attacked. I'm surprised it wasn't worse!

 

[TilliamWe]

Re: B3 Corrosion

Oh, that rear bearing carrier costs over $300. I would estimate that a shop will charge you about 3 hours to change it out.

 

[sailsmanship]

Re: B3 Corrosion

Thanks for the info and yes, I too can see the edge of the seal...

 

[Mischief Managed]

Re: B3 Corrosion

Hey Bill!

 

[hudman]

Re: B3 Corrosion

there is a lot of talk on the internet about mercruisers problem with b3 corrosion, according to the talk , these units were redesigned in 2000 to have less corrosion. lots of warranty problems with earlier units, that merc refused to replace under warranty... ill post the link if i can find it

 

[HT32BSX115]

Re: B3 Corrosion

Does anyone know if Volvo had similar problems?

 

[bigbrownbuku]

Re: B3 Corrosion

dp/sx volvos dont have near the corrosion problems the bravo 3 drive is prone too.<br />the key like mentioned is to keep up on the paint and if you can fit aluminium props. if you need stainless props paint them with edp and fit highly active aluminium anodes.<br />the mercathode system isnt perfect and requires some knowledge for it to be efficient. <br />in an area such as a river moorage the water may be flowing to fast for the mercathode. if you are moored at an older dock also. if you have a battery charger fitted thats not correctly grounded you will also contribute to drive corrosion.<br />if you own a bravo3 drive find a tech that can take some stray current readings around your boat and make the appropriate changes.<br />there is another anode you can fit to the end of the prop shaft as well but it is pricy.

 

[TilliamWe]

Re: B3 Corrosion

Good info Ben. Just want everyone to know, there are NO aluminum props for B3. No aftermarket props either. Just good ol Mercruiser stainless steel.

 

[Doug Durako]

Re: B3 Corrosion

Merc must be using inferior stainless these days because my B3 props have started to rust in a few spots where I took some nicks last season. Only 32 hours on the water.<br /><br />Anyone else noticed this on the dull stainless props (not the high gloss finish)????

 

[crazy charlie]

Re: B3 Corrosion

Those drives were prone to that type of corrosion.Personally,I would avoid them and go for a later year when it was corrected....ddboater--it really does not matter how good or bad a stainless prop is--if you nick it..it will rust,hi or low quality.

 

[TilliamWe]

Re: B3 Corrosion

Originally posted by ddboater:<br /> Merc must be using inferior stainless these days because my B3 props have started to rust in a few spots where I took some nicks last season. Only 32 hours on the water.<br /><br />Anyone else noticed this on the dull stainless props (not the high gloss finish)????

Yes, they are not polished. Never have been. And yeah they rust a little, but they don't rust away. Mine are 1997 model with 650 hours, and they have a little rust, but they still work great. If you keep it in the water they don't rust as much!

 

[Doug Durako]

Re: B3 Corrosion

Crazy---I never had a bit of rust in four years of running a Merc Laser2 on my old boat. The one before that ran 10 years---no rust. All fresh water running.<br /><br />I think they should call these new props steel, not stainless steel.

 

[TilliamWe]

Re: B3 Corrosion

dd, I'll give you a Central IL education, for free:<br /><br />They are called "Stain Less", not "Stain Free" or "Stain Proof". They rust less than "regular steel".<br /><br />If you think your blades look bad after you damaged them, wait til you take them off and see the hubs! <br />However you may have helped touch on something here. The ability of the B3 props to rust might indicate they help add to the corrosion issues of the aluminum on the drives.

 

[tommays]

Re: B3 Corrosion

i work with 304/316/316L stainless all the time on mixing machines.<br /><br /><br />Its allways interesting to see a LARGE 316L mixing blade make a galvinac attack a small 316 taper pin!!<br /><br /><br />tommays

 

[crazy charlie]

Re: B3 Corrosion

dd,put a coat of wax on it and call it a day.I didnt realize you were running in fresh water.What you see wont hurt a thing and the wax or polish will prevent it from happening again.Damn,you fresh water guys make me jealous!!

 

[Doug Durako]

Re: B3 Corrosion

Tilliam---you might want to investigate a bit further and take a closer look at a set of B3 props from 2005 or 2006.<br /><br />Older B3s have considerable shine compared to these new ones. The older Merc "satin" finish is shiny compared to these.<br /><br />Crazy---you can't wax these. I might try sandpaper or steel wool on the rust, but wax would be useless.<br /><br />I'll go over to the prop forum and ask my question.