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Discussion Starter #1
Was advised to add tabs for issue but from my experience tabs used help lower bow ,is it possible to use tabs to stop porpoising while still maintaining bow lift? Have flat bottom skiff that runs fine at all speed but at top end when engine trimmed out starts to porpoise. Have to leave engine tucked in and then that cause a bow down situation which is not good in a chop. Looking for advise on if tabs will allow me to trim out engine and adjust boat to keep bow up a little ,without porpoising.

Have engine cav plate level with bottom, tryied shifting weight around , and prop changes no affect on issue. Also check hull no issue with bottom.
 

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Lip Ripper
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My boat does the same without tabs, a couple taps of the tabs and boom i'm running solid again. I say get them, you won't regret it.
 

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I Love microskiff.com!
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Definitely worth it! make a boat run completely different!
 

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Discussion Starter #4
Yea think I'm going to just wondering if others had same issue. My concern was I tab down and porpoising will stop but may end up with bow down condition. So you able to stop porpoising but still maintain a little bow lift with combo of tabs and engine trim?
 

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I Love microskiff.com!
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Even if the boat didn't porpoise it's still one of the best addictions to fine run running in any conditions! They are expensive but will drastically help!!
 

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Fly-By-Night
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Without writing a book, a lot of porpoising comes from having the motor mounted too low and the cavitation (anti ventilation plate) enters the water at a low angle raises the bow till it gets too heavy the bow then drops......the cycle repeats. Even if you're going to add tabs I'd be willing to bet the motor is mounted too low. Cav plate should be 1/2"-1" or more above center-line running surface (depending on how far back your motor sits from the transom). Keep raising it till it blows out in hard turns then drop down one hole. If it's still bad enough to be a problem...then add the tabs.
Many builders, and others mount the motors too low IMO. Oh yeah if that's not enough motivation, you'll likely pick up a couple MPH too
 

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I Love microskiff.com!
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You should be able to reduce porpoising with correct motor trim and then fine tune further with trim tabs based on conditions like wind, chop, etc.
 

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Without writing a book, a lot of porpoising comes from having the motor mounted too low and the cavitation (anti ventilation plate) enters the water at a low angle raises the bow till it gets too heavy the bow then drops......the cycle repeats. Even if you're going to add tabs I'd be willing to bet the motor is mounted too low. Cav plate should be 1/2"-1" or more above center-line running surface (depending on how far back your motor sits from the transom). Keep raising it till it blows out in hard turns then drop down one hole. If it's still bad enough to be a problem...then add the tabs.
Many builders, and others mount the motors too low IMO. Oh yeah if that's not enough motivation, you'll likely pick up a couple MPH too

this doesn't hold true for all boats - the part concerning antiventilation plates/motor height


porpoising is also caused by too much weight aft,too much positive trim,hook in the hull and bottom flexing
 

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Zephyr Cove is on FIRE!
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Yes, trim tabs will knock down the porpoising issue and you can still adjust motor trim as well. My boat runs it's fastest with the motor trimmed out until it porpoises then I add just enough tab to kill it and she skates along perfectly. In addition to this tabs have many other uses like aiding holeshot and attitude when quartering chop.
 

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Discussion Starter #13
Thanks guys going to get those orders and install only thing I haven't tried hopefully it works .
 

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Fly-By-Night
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this doesn't hold true for all boats - the part concerning antiventilation plates/motor height


porpoising is also caused by too much weight aft,too much positive trim,hook in the hull and bottom flexing
You're right it doesn't hold true for all boats, but in my experience it has held true for most skiffs. If the motor is set back from the transom a long way, or he's running a pocket drive/tunnel etc it could be higher, but the op says he's running a flat bottom. The other things you mention are also very true, but the op said he's shifted weight around, tried different props, and has no hull issue. Either way, for me, raising it till it blows out on hole shot, or sharp turns then dropping down, gave best performance. That avatar is hilarious btw, I think I've had that guy work on a motor of mine in the past lol.

@Swe tabs are definitely nice, universal mania had a lenco kit for $450 a while back. Good luck and report back on how it goes.
 

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Balancing a boat is more important in my opinion. My dads 21 contender used to porpoise unless loaded down. It liked a full tank of gas (90 gallons) and a load of ice in the fish locker.
 

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Discussion Starter #16
You're right it doesn't hold true for all boats, but in my experience it has held true for most skiffs. If the motor is set back from the transom a long way, or he's running a pocket drive/tunnel etc it could be higher, but the op says he's running a flat bottom. The other things you mention are also very true, but the op said he's shifted weight around, tried different props, and has no hull issue. Either way, for me, raising it till it blows out on hole shot, or sharp turns then dropping down, gave best performance. That avatar is hilarious btw, I think I've had that guy work on a motor of mine in the past lol.

@Swe tabs are definitely nice, universal mania had a lenco kit for $450 a while back. Good luck and report back on how it goes.
Yes I saw those , any one buy from them before ?
 

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I Love microskiff.com!
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Yes, trim tabs will knock down the porpoising issue and you can still adjust motor trim as well. My boat runs it's fastest with the motor trimmed out until it porpoises then I add just enough tab to kill it and she skates along perfectly. In addition to this tabs have many other uses like aiding holeshot and attitude when quartering chop.
This. I start with the motor all the way down...then raise the motor bit by bit until I begin to porpoise slightly...then I lower it in small increments until the porpoising stops. That should be your sweet spot for speed with the minimal amount of hull in the water. And once you get to this point, you can adjust with the trim tabs based on conditions or etc.
 

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Fly-By-Night
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Yes I saw those , any one buy from them before ?
I bought a switch and control box kit from them a few weeks ago. They're legit. Fast shipping and the product was perfect. Can't speak to a whole tab kit, but I can't imagine they're any different.
 

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Zephyr Cove is on FIRE!
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This. I start with the motor all the way down...then raise the motor bit by bit until I begin to porpoise slightly...then I lower it in small increments until the porpoising stops. That should be your sweet spot for speed with the minimal amount of hull in the water. And once you get to this point, you can adjust with the trim tabs based on conditions or etc.
Here's what 33mph looks like when I run across the bay. Let her eat!
IMG_2736.PNG
 
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