Burned Blade??
 

First here's the specs just fyi:

Formula 353
Mercury Racing 525's
Mercury Racing I.T.S.
Labbed Bravo 32's

After running around this weekend the tip of one blade on the port prop looks like someone cooked it with a torch. I don't think I ever broke 3800 rpm all weekend so it was easy running and I know I never touched the bottom or anything else with it.

Anyone have any ideas what would cause this on only one blade??

Thanks for the help

Re: Burned Blade??
 

Is it possible to supply us with a picture?

Re: Burned Blade??
 

Well now that was pretty stupid of me wasn't it - unfortunately no - boats about 2 hours away and it'll be 2 weeks before I'm back to it.

Re: Burned Blade??
 

What's the condition of the particular blade with the burn (aside from the burn)? Is there anything along the leading edge such as a nick, bend, crack, etc? What about the trailing edge of the burned blade and the blade before before the burned blade? Does the burned blade seem to be bent up or down (when placed on a table)?

Matt

Re: Burned Blade??
 

I haven't gone so far as to take the prop off the boat, but I did give it a good exam and near as I can tell there is absolutley nothing wrong with it or different from anyother blade. No nicks, no signs of cavitation, no bends (that I can see) - nothing. It simply looks like the very tip of the blade (maybe the fisrt inch to inch and half) got hot. It was a real mystery to me so I figured I'd look to those on OSO who know more about it.
Thanks

Re: Burned Blade??
 

When you get the opportunity post a picture. The blade tips travel at the highest speed, about 300 mph, so they are most prone to have issues.

Is the metal discolored as if it was heated? Since you only had problems with one blade the problem probably lies with that blade or the one before it.

Matt

Re: Burned Blade??
 

During the production process at Plant 98, (Mercs propeller facility), a casting may come out of the mold with "fixable" porosity in large sizes, it may be welded prior to balancing and media finish. Depending on its size and the quality of the weld and tech.'s ability, the spot may be evident to the eye after media finish and can show up even better after it is run on a boat. We have had many discussions about this over the years at Mercury. Good arguments from both sides.

Obviously I can't make this judgment call on your prop without seeing it but it is a legitimate possibility due to the explanation you are supplying.

Re: Burned Blade??
 

I'll get a pic when I can, but it'll probably be two weeks. While I've got the pros - if I wanted to change props - what would ya'll recommend given my set up. My first priority would be to improve mid range speed, but like everyone else I want higher top end, higher cruise and better hole shot - not much to ask for right?!?!? I've heard that formula is having good luck with 5 blade props on the 353 because they tend to carry the bow more - any thoughts? Again thanks for the help.
Reed

Re: Burned Blade??
 

Before making a suggestion on props for your application what are your current performance numbers? Is there anything you like or don't like about your current props?

Matt

Re: Burned Blade??
 

I'm just looking for possible performance increases - currently the boat runs right at 50mph at 3500 - 3600 rpm. WOT/5200rpm will get me approx. 84mph, but I'm not a wot kinda guy. Whole shot is a little sluggish, but not a problem. The boat has one funny characteristic in that starting from idle the boat will lumber along until the engines hit roughtly 3000rpm. Once they cross that its like something exloded and they shoot to 4000 plus unless I pull back on the throttles and let everything settle in. I'm not sure I think that's a prop issue, but it's the one thing I'd really like to change if I could.