Porpoising Help!!

[jamieat]

Re: Porpoising Help!!

Finally! Someone seems to think it is something directional going on with my hull. That is my impression anyway. I have emailed Xpress, and of course, have yet to get a response. I am wondering, since there is a lifetime warranty on the hull, and if I could prove that the cause of my problem is in the hull, if they would make good and repair it.

 

[MikDee]

Re: Porpoising Help!!

I'm gonna go against the naysayers here, and recommend a Doel fin! I think you'll be pleasantly surprised, but either way what have you got to lose? There are just some instances where this does work, even if it's temporarily, or (permanently) in place of trim tabs. It keeps my boat planted in choppy water, rather then slight porpoising.

IMO, what's happening is prop torque in a straight line is causing porpoising, you are yielding to some prop torque by turning left, hence no porpoising.

 

[jamieat]

Re: Porpoising Help!!

Stupid question but, with a doel fin, do you drill holes in the cavitation plate for installation or do they slide on or what is the mounting procedeure? This is causing me such a headache. I want to get this issue resolved. Do you believe that going up to a 21p would help at all?

 

[MikDee]

Re: Porpoising Help!!

Stupid question but, with a doel fin, do you drill holes in the cavitation plate for installation or do they slide on or what is the mounting procedeure? This is causing me such a headache. I want to get this issue resolved. Do you believe that going up to a 21p would help at all?

Doel fin, Yes, you slip it on then drill 4- 1/4" holes in your cav plate 2 on each side, no big deal,,, if your not satisfied, take it off, pop rivet the holes, or fill the holes with marine tex, whatever. You can always save your money, & get smart tabs if you notice an improvement with the fin, or just keep it as is. I don't think going to a 21" pitch is gonna solve your problem

 

[jamieat]

Re: Porpoising Help!!

Ok, another question. If I go with the smart tabs, do I have to get auto adjusting tabs to ensure that I am able to modify it to perform the task I am trying to accomplish. Or, will just about any serve the purpose? Any suggestions/ price ranges?

 

[LubeDude]

Re: Porpoising Help!!

You need to measure your prop shaft to pad hieght and let us know what it is. It should be somewhere around 3-4" for most applications. Starting at 4" and going up to find the sweet spot.

Maybe that Hustler prop does not have enough bow lift!

 

[jamieat]

Re: Porpoising Help!!

Also, what about mounting the tabs? Is there additional wiring or tubing that has to be ran for pneumatic/adjustable tabs? I am just trying to get a hold on exactly what I will be getting myself into. Are they something that can normally be done yourself, or is it better to seek professional help? Any advice about these is greatly appreciated.

 

[jamieat]

Re: Porpoising Help!!

Right now my prop shaft is approx 2" below the pad. I have experimented with adjusting it anywhere from 4" below to almost parallel. Went all the way down on the jack plate to up to the point where I was losing water pressure. I have tried adjusting it up and down to the point I just dont know what else to try. Thanks so much for everyone on here giving me input!

 

[jamieat]

Re: Porpoising Help!!

HHHHMMMMMMMMMMM

 

[LubeDude]

Re: Porpoising Help!!

Sounds to me like we are at a point of saying that the boat is just a bit underpowered for what you expect it to do. Yes, it seems to me that that 90 should do the trick, but if it will not hold the nose with the weight you have, then it's under powered or your prop just does not have enough bow lift built into it. You probably could bennifit buy having your prop worked for more lift..

You may have to live with only being able to trim as far as the boat tells you that you can. (As per my first post)!

 

[jamieat]

Re: Porpoising Help!!

Well, I dont think that the boat is underpowered. The max hp rating for the boat is a 90! Also, it will run approx 53 mph with one person, which is pretty good for a 90. Anyway, seems like I have no choice but to purchase some trim tabs and see how that helps. What would be the max you think I should spend for some tabs for this type of setup for some good ones?

 

[MikDee]

Re: Porpoising Help!!

I still say you should get a Doel fin instead, if your boat has a speed designed hull, as it appears, it is on the edge at WOT, meaning it wants to constantly lift out of the water, it is "skittish" the fin will calm it down, & make it appear as a larger boat, without a bigger investment. Sure you can buy the Smart tabs, but either one will lift the transom at speed, and put the bow down, but the tabs may overdo this when you want to get the bow up in rough conditions, especially because your boat is rather small.

Bennet adjustable tabs are a headache, esp. on a small boat. They're expensive! I've had them, but only because on a deep vee 24' boat that would not ride level at any speed without them, there is no trim guage, so you never know exactly where they are? and there is a slight delay in their response, and every change in direction, or current, or wind gust, you're adjusting them, and you never know how much until they take effect, and or if you move them the wrong way by mistake, you might be in trouble, finally when you back off the throttle, and forget they're engaged, your boat may lurch, or lean to one side till you correct them, Plus don't forget to put them both up, if not needed, or you'll fell like you're dragging your anchor, and kill your gas milage. No, to me they are a last resort.

 

[jaxnjil]

Re: Porpoising Help!!

Anyone have any suggestions about trim tabs? Brands, size? Hydrolic, Pneumatic, manual, fixed? Which ones would you recommend for my setup and boat size? Thanks

What Trim Tabs Do










Most boats are designed to plane at a particular speed and weight distribution. However, as weight increases (due to additional fuel, passengers, or gear) and/or speed decreases, the stern settles down creating an inefficient, untrimmed condition. As the boat pushes forward, it creates a "hill of water." In this bow-high position visibility is limited and the hull bottom is pounded. In addition, due to significant hull drag and extreme prop angle, fuel economy is poor. Properly sized Bennett Trim Tabs enable your boat to overcome this "hill" and plane at speeds slower than designed planing speed.

As the helm control is pressed, the stern rises, lowering the bow. Without touching the throttle, speed increases and optimum attitude is achieved regardless of speed or weight distribution.

Bennett Trim Tabs reposition the boat's bow to cut through the water reducing pounding, drag, and engine laboring. Repositioning the bow creates greater visibility which increases safety. Reduced pounding means greater comfort. Less drag and engine laboring translate into increased performance, greater speed, and reduced fuel consumption.

With all the advantages and efficiencies created, Bennett Trim Tabs virtually pay for themselves.

http://www.bennetttrimtabs.com/



if you want the best and dont mind getting the best factory support in the busniess go with bennett

 

[Ted Bell]

Re: Porpoising Help!!

Here's my experience, worth about what you pay for it. I put a new Evinrude E-tec 60 hp on my boat last year, a 16' 1959 mahogany Whirlwind. At full throttle it would porpoise horribly, regardless of how you trimmed the motor. It was horrible, and very, very frustrating. I spent all winter doing research, and decided to try the Smart Tabs. Put them on about a month ago - easy installation, no adjustments to make. Took the boat out and absolutely zero porpoising. It is unbelieveable-just a beautiful, smooth ride. They cost me about $120, but if someone had put them on my boat and let me try it and experience the amazing difference, then told me they cost $250, I would have paid it in a heartbeat. I can't recommend them strongly enough. Hopefully you will have as good a result as I have.
-Ted

 

[QC]

Re: Porpoising Help!!

Tabs look like you know what you're doing, plus they actually work. Doel fins look M-I-C-K-E-Y M-O-U-S-E and well . . . OK, so they work sometimes.

 

[oldtruckface]

Re: Porpoising Help!!

Ok ,the boat is pretty new so there shouldnt be one but have you taken a long
strait-edge and place it on the center of the hull at the stern, if there is a hook
10 - 30 inches from the transom then it will 'porpoise' only when going straight
by hook I mean bulge or indent or anything that is not 100% straight,
I filled in a hook on a 75 invader with a 150 merc and the problem was gone

__________________________________________________
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