Bravo 3 Propeller Problems (Cavitation & Cracks)
12-26-2003, 11:25 PM
#11
Ginger or Mary Ann?
Charter Member
Re: I Don't know how
Originally posted by HOUSTONPROP
you did that,??But ThankYou!
Thanks US1FOUNTAIN,for putting a little light on the subject.
Darin
you did that,??But ThankYou!
Thanks US1FOUNTAIN,for putting a little light on the subject.
Darin
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Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
Last edited by US1 Fountain; 12-26-2003 at 11:55 PM.
12-27-2003, 12:19 AM
#13
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Absolutely. Front prop on both drives new also. Switched from 26" to 28" and 26"s had same problem but were the older casting without the "B" stamps and were immediately replaced with 28s when the exhaust upgraded and all rear 26s cracked (3).
After first couple of 28" props I smoothed front prop thinking a burr might cause cavitation on rear, but to no avail.
Nothing on bottom to cause cavitation either and same problem occurred with original Bravo 3 drives as is occurring with new Bravo 3Xs. The 400SS is a stepped hull. Hope your feeling the pain and frustration!!!!! (And I do appreciate any suggestions and help.) Hopefully somebody else with the same problem will find their way to this thread and it will assist them.
After first couple of 28" props I smoothed front prop thinking a burr might cause cavitation on rear, but to no avail.
Nothing on bottom to cause cavitation either and same problem occurred with original Bravo 3 drives as is occurring with new Bravo 3Xs. The 400SS is a stepped hull. Hope your feeling the pain and frustration!!!!! (And I do appreciate any suggestions and help.) Hopefully somebody else with the same problem will find their way to this thread and it will assist them.
12-27-2003, 05:07 PM
#15
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The Bravo 3 props are available both with and without cup. Have you tried a set with cup? Seems like the cracks are caused by the cavitation, cup may reduce or eliminate the cavitation as long as the cavitation is not caused by some other source than the props.
As far as the rust goes I would have to disagree. The Bravo 3 props are made of "true" stainless steel. The Bravo 3 props have a satin finish which will rust much faster than a polish finish. Even overnight, and this is true with just about any satin finished prop, some more than others.
There are more stainless alloys than you can count. Stainless steel is just what it is called; stain-less. It's not called stainproof. If they were steel they would be completely covered with heavy rust. Props have to use a high strength alloy to survive in the environment in which they work.
The "marine" grade stainless is 316, which is not magnetic. It is the most resistant to corrosion in the marine environment. 316 is not strong enough to make a prop with. Most Mercury props are made with 17-4 Stainless steel which has a tensile strength twice that of 316. Herring and Hydromotive use 15-5 Stainless Steel, for a very specific reason, which has different properties than 17-4 . Of course every lot of props made have a slight variance in the composition of the alloy used so some may rust a little more than others.
Matt
As far as the rust goes I would have to disagree. The Bravo 3 props are made of "true" stainless steel. The Bravo 3 props have a satin finish which will rust much faster than a polish finish. Even overnight, and this is true with just about any satin finished prop, some more than others.
There are more stainless alloys than you can count. Stainless steel is just what it is called; stain-less. It's not called stainproof. If they were steel they would be completely covered with heavy rust. Props have to use a high strength alloy to survive in the environment in which they work.
The "marine" grade stainless is 316, which is not magnetic. It is the most resistant to corrosion in the marine environment. 316 is not strong enough to make a prop with. Most Mercury props are made with 17-4 Stainless steel which has a tensile strength twice that of 316. Herring and Hydromotive use 15-5 Stainless Steel, for a very specific reason, which has different properties than 17-4 . Of course every lot of props made have a slight variance in the composition of the alloy used so some may rust a little more than others.
Matt
12-28-2003, 01:38 AM
#16
Ginger or Mary Ann?
Charter Member
Matt, why would a satin vs polished finish be more prone to rusting? Same material, just a different finish.
Also to add to your SS lesson, some stainless alloys do have magnetic characteristics. In other words, some SS are magnetic. Just a bit of info.
Also to add to your SS lesson, some stainless alloys do have magnetic characteristics. In other words, some SS are magnetic.
Just a bit of info.
__________________
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
12-28-2003, 08:35 AM
#17
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Yes, you are correct, some stainless steel is magnetic. That was my point, even though your props are magnetic they are stainless steel. A magnetic is not a definitive test to determine if the material is stainless or not.
Since satin props have a "scratched finish" much more of the meta isl exposed, therefore corrosion is much greater with a satin finish. That's why with a polished prop the inside of the can will rust before the blades do.
Matt
Since satin props have a "scratched finish" much more of the meta isl exposed, therefore corrosion is much greater with a satin finish. That's why with a polished prop the inside of the can will rust before the blades do.
Matt
12-28-2003, 11:10 AM
#18
Ginger or Mary Ann?
Charter Member
Thanks. I always wondered why non polished SS parts were more likely to show rusting, but never knew why.
Yes, the magnet test/check is a misconception about SS. that I see mentioned here all the time.
Added Note: Only mentioned this as a general observation whenever this comment is mentioned on any topic. Not meant to question the knowledge of anyone in this topic.
Yes, the magnet test/check is a misconception about SS. that I see mentioned here all the time.
Added Note: Only mentioned this as a general observation whenever this comment is mentioned on any topic. Not meant to question the knowledge of anyone in this topic.
__________________
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
Last edited by US1 Fountain; 12-28-2003 at 01:23 PM.
12-28-2003, 01:07 PM
#19
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BravoIII PROPS
ARE YES BOTH CUPPED AND UN CUPPED ,BUT THERE ISNT A PROP THAT IS NOT magnetic,this is due to the high carbon count in the props more steel,than stainless,as far as stain finished props on the BravoIII the are not they have a dura tumble finish which is very smooth and has no deep surface scratches what so ever,they are totally different thana qoute SATIN FINISHED PROP.but in the same essence they are not polished either.
bottom line is looks like there are some casting issue's as far as tensil strength causing them to break,or they Mercury would not be re-placing them like this.
bottom line is looks like there are some casting issue's as far as tensil strength causing them to break,or they Mercury would not be re-placing them like this.
Last edited by HOUSTONPROP; 12-28-2003 at 01:10 PM.
12-28-2003, 02:11 PM
#20
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Even if there are casting issues that still doesn't explain what's causing the cavitation.
Actually there is almost no carbon in any stainless alloy. The rust has to do with different levels of Molybdenum and Nickel in 17-4 stainless as opposed to 316 stainless. There is less than .07% carbon in 17-4 and 316 stainless.
Matt
Actually there is almost no carbon in any stainless alloy. The rust has to do with different levels of Molybdenum and Nickel in 17-4 stainless as opposed to 316 stainless. There is less than .07% carbon in 17-4 and 316 stainless.
Matt
