Skeg Modifications 2017

dubmoney

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Guys I am on my third lower unit, and the newest one came with a huge torque tab! The biggest handling issue with the newest lower unit was high speed porposing. I decided to start grinding away at it to make it look more like the last two lower units I ran. Both of them had very little torque tab.

Question is how do I know when to stop grinding. Theory tells me that the less torque tab you have the faster you will be, but it may be hard to drive. How do I find the perfect balance? Any thoughts?

My first lower, it looked like someone had dished out the starboard side of the skeg, ever so slightly, with almost no precieved torque tab at all, that seems like the best idea, but wonder if any one would share their secrets.

I also wonder if there is an optimum trailing edge angle and minimun safe length.

I run xb 2003 1/4 under pad, ( I looked over the back deck last night and could see the tip of the bullet at 55 mph.) it seems high to me, blown out lots, thinking about sanding lip, becuase the bow just won't trim out, so hull runs clean. I sanded is a little yesterday and it seemed to help.

My moter is 260 ported, no rev limit, best top speed 95 mph. with 28 Mazco RE3 worked by DAH.

Any experience or advice would be appriciated.
 

bassracr

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Do yourself a favor , don't go sanding on your boat just yet.And grind on your gearcase only if you know exactly what your are doing . Otherwise leave it to a professional . It's the only way it will drive and run right. I sent mine to Robbie Patterson . Re measure your prop to pad . I'm guessing you are higher than you think. You will be around folks that should be able to help you if you will be attending the rally . Maybe a different prop will help you get the bow up more ,or lower the motor? More setback needed? maybe the boat runs (proper) flatter than your expectations ? I would exhaust all other options before I started removing material .its expensive to put it back on .I'm confident you will get it figured out.
 
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GotMyAlly

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How do I find the perfect balance? Any thoughts?
How's the steering torque? That's how i would gauge the need for more/less torque tab. It should pull to the right pretty hard without it. If you've got too much tab, I'd think it would pull to the left.

I worked one of mine until it actually pulled to the left ever so slightly at some mid range speeds, but as speed increased it evened out and at top end it was perfect.

I definitely don't think you want to remove it altogether, but tweaking it may be necessary, especially if it is overly large.

I doubt the tab is to blame for a high speed porpoise though......
 

flying07

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Call Todd Bucknell at Hydromotive, and ship the lower to him. He worked a little 'magic' on my lower unit, best thing I ever did! Drove waaaay easier, and was almost 2 mph faster, same prop. Get a professional, like Todd, to get it set up correctly.
 

dubmoney

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Thanks fellas for your input. I realize I might just need more time on the water to more fully understand what the boat is doing. I took some video of it running over the weekend, and with video analysis and your advise, hopefully I can make the right decisions about set up. I wish I had the money to send out my lower unit, or try anther Lower Unit guru, but I have spent my allownace already for the year, and the season is just getting started.
 

dubmoney

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I removed more of the torque tab, and flattened out a bulge in th lower unit casting and took it out for a spin last night and handling was better. It was windy so only felt comfortable up to 82 mph.
 

SLOmofo

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Any change requires remeasuring prop shaft height. Only one change at a time. Don't, sand the pad. Get ahold of Bill Smith aka bad bait, he is a very knowledgeable XB 2003 owner.
 

dubmoney

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Update: I have been using a long board with 80 grid to shap the skeg the way I believe will net me the best performance. I have used a 4" grinder with a flap wheel, a dremel tool, and a file. I know these pictures don't really show very good how big the torque tab is, but this is after 4 hours of sanding. I would go faster on the next one, I am just taking it slow, as not to take to much off of the wrong area. I took it out after this picture, and she runs really straight, like no hands on the wheel. The Seastar system, I can feel almost no tendency to turn one way or the other. Top speed with full tank of gas, trolling motor, two people, 60 lbs of ballast, and small cooler, and misc items, was about 86 mph. I plan to sand on the tap a little more. All porpoising is gone, so I feel like I am on the right track. I wish I knew if it was the bulge in case that was causing the porpoising or the torque tab.20170522_142357.jpg 20170522_142417.jpg 20170522_142447.jpg
 

catfish123

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I do not believe the torque tab would have anything to do with porpoising.
 

dubmoney

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I believe it was the torque tab that was so big it was disturbing the water so much the prop could not bite like it should. Actually, I think it created drag, which led to porposing, Everything else was the same on my boat except the lower unit. Same prop, Same wieght distribution. Now, what is the consensus on the blow out ring, can I get any more speed by massaging that a little? I really dont understand why the blow out ring needs to be there, although it seems that plenty of smarter people than me say it does.
 

dubmoney

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I agree Chris it is on my list to epoxy the outside two holes, now that you mention it, I will probably do it sooner rather than later.
 

gmorgan

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I've been told that the blowout ring collapses air bubbles that otherwise would reach the prop.
 

dubmoney

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msethsmile, I have seen this document before but never noticed the measurment for the amount of skeg turn to the starboard side of the boat. It says 3/16 of an inch!! That is about what I had on the first two lower units. I think I am at about 1/4 to 5/16 now, so I will go down to 3/16 and call it good. Thank you very much!! This is the type of advice I was hoping to to base my decision on.
 
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