update on how the deckover is doing.

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jopete
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update on how the deckover is doing.

Post by jopete »

after a few hiccups, i have my 12' deckover running great. good oil pressure, no issues.
just put the headers/mufflers on it and they look good and aren't too loud.
just changed out the expanded metal on the cage with 2x4 wire and that is all good now.

now if i could just get rid of the porpoising, i think i might enjoy driving the boat. right now if you try to go past 1800 or so rpm's expect to get a rodeo ride. lol

when i get some time i am gonna drop the prop end of the motor down some and see what happens. it's either that or get a trim tab i guess.

are there any other fixes for the dreaded boat hop that i am overlooking.?
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Birddog247
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Re: update on how the deckover is doing.

Post by Birddog247 »

Sounds like you may have a bad hook in the center of the hull. I would try and shim or jack the center down a Little first.
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KR23
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Re: update on how the deckover is doing.

Post by KR23 »

post a picture of the boat, start simple. Change to much and you could make it worse. If it is a true Don Davis it is made of 7075 which is a lot harder than the material used on others. Post some pics of the boat, you never know your rigging could be your problem. Level the boat by using the runners inside the boat then check the motor angle. seen it plenty of times where the rigging is the problem.
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John Fenner
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Re: update on how the deckover is doing.

Post by John Fenner »

Yes, drop prop end down
I never finish anyth,,,.
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Deano
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Re: update on how the deckover is doing.

Post by Deano »

If it is on the trailer, running a string line under the boat from the bow to the stern will
allow you see if it does or does not have a hook, and if so, where and how severe it is.

If it is not flat, that will show you where to position your jack and roughly how far you need to go with it.

If it is flat, all is good and the expectation would be that doing as John said, will completely solve the problem. :thumbleft:
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Re: update on how the deckover is doing.

Post by John Fenner »

A string will show dents, however a straightedge is best suited for fine tuning. If it rocks fore and aft anywhere from transom edge forward to say a foot or so it will hop.
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Re: update on how the deckover is doing.

Post by jopete »

thankyou for the reply's guys. i really do appreciate all the information that Y'all pass along. it's one of the reasons that this is such a great place.

after i get some honey-do's done this morning i am going to mess with it a bit and see if i can figure some stuff out.
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Re: update on how the deckover is doing.

Post by jopete »

bottom looks straight.
going have some small trim tabs bent. gonna go pick them up and bolt them up this afternoon. that ought to fix it.
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Re: update on how the deckover is doing.

Post by Deano »

If it's aluminum and it has a lip at the bottom of the transom, you can just take a big crescent wrench and pry the lip down just a little bit and accomplish the same thing with less grief. If it has no lip, well then . . .
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KR23
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Re: update on how the deckover is doing.

Post by KR23 »

if he has a true don davis its made of 7075 and you aren't going to bend it with a wrench
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Re: update on how the deckover is doing.

Post by jopete »

I don't know, but my paperwork says it's a 1984 Don Davis built 12' airboat. the rake and storage box were built local. don't know about the rigging.

if it's not a Davis hull, somebody let me know. all i know is that it's a bouncing son of a bugger right now. lol

i had some trim tabs bent, but i can't make myself drill holes in the boat today. gonna think about it a while.


after talking to the previous owner, i see where he changed the motor mount near the prop. there is no room for adjustment. might have to get creative to get some adjustment out of it.
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jopete
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Re: update on how the deckover is doing.

Post by jopete »

Deano wrote:If it's aluminum and it has a lip at the bottom of the transom, you can just take a big crescent wrench and pry the lip down just a little bit and accomplish the same thing with less grief. If it has no lip, well then . . .

i have done this on my other boats, but the lip is pretty short on this one. i don't know if there is enough lip to grab. i may get a 2x4 and a hammer and 'whack it' a few times and see. !!!
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Re: update on how the deckover is doing.

Post by Afflicted »

Hell if u can bend it any it'll help or fix it. 1 time when I drove my boat on dry then when we got in the water it was hopping bad. Felt like it was coming out of the water. Hip the lip on the back a few times with a hammer ( it looked absolutely no different) but 100% fixed it
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Re: update on how the deckover is doing.

Post by Ted Martell »

Check your cross runners if one of them is broke it will let bottom flex to much and hop if you do any thing with motor raise it up a little about 1 or 2 washers in back not down
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Re: update on how the deckover is doing.

Post by Seven3 »

Does your title say Don Davis, or does the bill of sale call it a Don Davis? Ive had three Don Davis's and they were all listed as homemade on the title. Post some pics of the transom and inside the hull and I'm sure someone could tell you who built it.
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Re: update on how the deckover is doing.

Post by jopete »

Seven3 wrote:Does your title say Don Davis, or does the bill of sale call it a Don Davis? Ive had three Don Davis's and they were all listed as homemade on the title. Post some pics of the transom and inside the hull and I'm sure someone could tell you who built it.

that is very interesting. He might have sold me a Sanford & Son hull. in La, you get a title on the trailer, not the boat.
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Re: update on how the deckover is doing.

Post by Deano »

Ted Martell wrote:Check your cross runners if one of them is broke it will let bottom flex to much and hop if you do any thing with motor raise it up a little about 1 or 2 washers in back not down
This is just plain WRONG; in fact that is backwards.
Raising the rear (prop end) of the engine will raise the bow.
Lowering the rear (prop end) of the engine will lower the bow.
If it is porpoising and the bottom is straight, the remedy is to lower the
rear of the engine (and the bow), just as John and I have already pointed out.

There is an expanded explanation of that here:
http://www.southernairboat.com/phpBB3/v ... 85&t=28600
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Re: update on how the deckover is doing.

Post by Deano »

Jopete, If the bottom is in fact straight, I would encourage you to pursue the engine angle before you make changes to the hull. If the angle of thrust is the culprit, hull changes are not needed and could likely make correcting it more complicated.

If the rear mount(s) doesn't allow for adjustment, is it possible that the front would?
Raising the front a little (a washer or two), would have the same net effect as lowering the back.
You only need to alter the angle of thrust a little bit, which way that is accomplished is of no consequence.
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Re: update on how the deckover is doing.

Post by stroked470 »

Deano, how many riveted Deck over boats you had???? Never seen someone comment on stuff that they know nothing about like they are an expert. Anyone that starts off saying "if it's alluminum" and then says to bend the Tbar at the transom on a riveted 7075 boat has no clue what they are talking about. TedMartel is correct in if the runner cross braces snap it can let the bottom flex and cause major porpoising issues. Give advice on subjects you know.
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Re: update on how the deckover is doing.

Post by Seven3 »

I've never seen anyone bend the T Bar lip on a riveted transom, but I would assume that would lead to separation of the three parts that connect there (T Bar, bottom sheets, and transom sheet) and cause leaking.
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Re: update on how the deckover is doing.

Post by stroked470 »

Eric that is 100% correct man
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Re: update on how the deckover is doing.

Post by Ted Martell »

For those of you that don't know when a boat starts to hop it is most of the time riding to much on the bow an is trying to rise there for if you pick prop end up it will bring bow up most of the time if a boat is hoping it is real close to perfect it only takes a minor adjustment.my brother and I have only had,built and been around air boats for the last 40+years so I mite know a little tiny bit but then that's a lot of what's wrong today to many mouths In gauged before brain
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Re: update on how the deckover is doing.

Post by Deano »

Stroked470, I guess I failed to convey enough, that my comment pertaining to what Ted wrote was confined to the engine trim and the associated angle of thrust and had nothing to do with the cross bracing. That is why I highlighted that part of the quote, as that part is what I was responding to. In spite of his subsequent post, I will stand by what I wrote in that regard as I know it to be true, even with a riveted deck over.

As far as my "bending the lip" comment goes, that was at the beginning of the thread and I had not seen Jopete's Signature line or KR23s reference to the 7075, so obviously didn't realize that he had a riveted hull. MY BAD. Even my dumb ass would know better than that. :roll: I became aware of that only after it was pointed out in a subsequent post, at which time there was little I could do about having already shown my ass. :oops: Distractions promote poor reading comprehension and retention skills. MY BAD AGAIN.

If you knew me, you would know that I have never had any intent or desire to come off as an expert about anything; let alone a riveted hull of any kind. There are many subjects and debates on SA that you never see me comment on and that is why. Unlike some others on this board, I am content to stay STFU when and where I don't know the subject matter.

Since this appears to be one of those . . . I'll watch and learn . . . y'all go ahead. :salute:
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Re: update on how the deckover is doing.

Post by jopete »

yep, after i whacked the lip on the transom with a rubber hammer a couple times, i realized that i was not gonna bend that lip. lol i had no idea that it is probly a t-bar.
deckovers are rare as a unicorn where i am in south la, so it has been a learning experiance.

i pulled out my dry storage box and looked around as much as i could and didn't see anything broken.

i will try to post a pic of the prop side motor mount tomorrow. the previous owner didn't like the peice of all-thread that was there and made some type of engineering masterpeice on there. looks like i might be able to take it off and cut off a half inch or so then put it back. i am thinking he inadvertedly raised it up some.

that huge 3' grass rake is probly some of the problem as well. the faster i go, the more air it grabs and lifts the front. it is nice in the grandovollies and sliding down the bank at my camp.

on the bright side, i went ahead and put in a new 2000gph bildge pump and got to see what it looks like under the deck. it appears to be rhino lined everywhere under the deck. that will be fun when it comes time to redo the teflon. lol

i am still excited about the boat, i am determinned to get it right !!!!!!!
thanks again for the responses, i appreciate ALL posts!!!

here's a few pics of my previous airboats.....
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Re: update on how the deckover is doing.

Post by Ted Martell »

I would not have said anything at all about this matter had I not had the same problem with the boat I have now it is a 12 ft riveted diamond back deck over with a big grass rack .i raised it 1/4 inch in back after lowering it first witch made it worse after putting it back then raising it the boat runs great with the fuel injected 520 on it . The change was so good I took of the trim tab they had put on it be for I had bought it. The trim tab hadn't worked either what fixed it was the 1/4 in.raise in the back so much for deanos post about me being wrong but now my boat is not the only one we have fixed.you do what you want its your boat but seams to me raising the back up is the easiest thing to do first then go from there i am not saying this is a guarantee just what I have done in the past which is more than I can say for some of the rest
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