350 dd boat pushing down in back

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bassinflats
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350 dd boat pushing down in back

Post by bassinflats »

HAVE ALREADY POSTED QUESTION ONCE, BUT HAVE PUT SOME PHOTOS IN MY ALBLUM, UNDER WATER TEST OF BASSINFLATS. EVRY TIME I WENT TO APPLY POWER BACK DIPS DOWN AND WANTS TO TAKE ON WATER. AM THINKING I SHOULD SHIF WHOLE CAGE AND SEAT STAND FORWARD AND MOVE FULE TANK UP FRONT. ALSO SHOULD I SHIM THE MOTOR UP IN BACK, REALLY NEED SOME HELP ON THIS AS THIS IS OUR FIRST BUILD. HAVE BEEN ON OUR OWN SINCE WE HAVE STARTED THIS PROJECT AND YOU ALL ON THIS WEB SITE HAVE REALLY HELPED US OUT SO FAR, DON'T KNOW HOW WE HAVE GOOTTEN THIS FAR WITH OUT THE SITE. THANKS FOR ALL AND ANY INPUT AND IF YOU CAN GO TO THE PICTURES YOU WILL SEE WHAT I AM TALKING ABOUT. :bounce:
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SwampMatt
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Re: 350 dd boat pushing down in back

Post by SwampMatt »

is it the whole stern that dips or mainly one side?

Oh, and generally speaking, if you raise your rear motor mounts, you raise the bow.
(what you do to the rear mount is what you do to the bow)
So if you do tweak the motor angle, you'll probably want to lower the rear mounts (or raise the front)
But that's just minor adjusting. Don't count on it to fix something major wrong in your setup.

crabby
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Re: 350 dd boat pushing down in back

Post by crabby »

What prop are you running
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SwampMatt
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Re: 350 dd boat pushing down in back

Post by SwampMatt »

Image

I found your photos.
In this photo, what's making that right rear corner dip is torque roll. AND the slow speed turn. I.M.O. But it's usually a left turn that is the deadly one. Centrifugal force of the turn works with the torque roll and really pushes that corner down.

Be careful about when you let off the gas in deep water. Your wake (if you were on plane) can just wash right over the transom and you'll be on the bottom 10 seconds after that.

Image

I don't see anything out of the ordinary in this photo. I suppose you could slide the whole package forward a few inches. It'd mean another 6 holes in your stringers (seat/motor rails) + 4 in the hull (cage). But what the heck, try it out before you glass over the old holes.

Olf Art
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Re: 350 dd boat pushing down in back

Post by Olf Art »

That boat turned out really good lookin. Since you're already a 'front driver', weight shift probably won't help much. If it was mine I'd look at motor angle. The engine/prop thrust line may be too high to the rear, which is trying to push the transom down when you add power.

Can you lower the rear of the engine some with your mounts?
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lanny haff
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Re: 350 dd boat pushing down in back

Post by lanny haff »

I had a boat set up like yours I took 2 pieces of 1/8 diamond plate 8' long 8'' wide and raised up the top rail that goes around the top of the hull from the transom forward and put them in between so I actually made the rear of the hull higher. I also made a piece of diamond plate 6'' wide with a 1'' lip and bolted it to the transom 2'' from the the top to form a shelf to keep the water out when slowing down. Both of these mods helped.alot
nice looking boat good luck Lanny

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JAMES
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Re: 350 dd boat pushing down in back

Post by JAMES »

MY 12' COTTONMOUTH WAS A LITTLE LIKE THAT AND I SUNK IT DOING WHAT YOUR DOES LOW RIDING AND SITTING TO LOW IN THE WATER JMO MOVE GAS TANK FORWARD AND TILT MOTOR SLIGHT BIT IF THAT DONT WORK MOVE THE WHOLE RIG A FEW INCHES FORWARD IT MAY HELP GOOD LUCK :roll:
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John C
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Re: 350 dd boat pushing down in back

Post by John C »

bassinflats, who made your hull? And how long and wide is it?

Canes350
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Re: 350 dd boat pushing down in back

Post by Canes350 »

that is what my boat looks like. i think my boat even sits a little lower in the water. when slowing down in deep water i have to slow down then speed up to get away from my wake or i think i would go down. :lol: everybody told me that it isnt a good hull for a first boat
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captain chad
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Re: 350 dd boat pushing down in back

Post by captain chad »

I realy don't see anything wrong with the setup i realy wouldn't go slidding the rigging forward. I was wondering does your motor have the guts to get the boat on a plane? If so then stab the gas and let the motor and hull get the boat on a plane. If you move the rigging forward the boat will not handle as good and you might get in trouble that way, I would level the motor and go from there. But you want to make sure your motor is performing right. This is just a question do you have any experience driving airboats. If you dont then you might want to ask someone from this site to come down and run your boat before you make any changes. It looks like from your pics the boats setup right. 8)
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calbrigsr
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Re: 350 dd boat pushing down in back

Post by calbrigsr »

I agree with moving the gas tank forward.
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plumcrazy
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Re: 350 dd boat pushing down in back

Post by plumcrazy »

bigger boat or a air craft motor 4 cylinder, probalys gonna be the anwser to your troubles , the silver lining is that rig will make you into a great airboat driver, had one like it a long time ago drove it for a while , sold it to a friend and he sunk it the first time out , it will help to move every thing foward, doe it porpoise when you have on plain in deep water :?:

Olf Art
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Re: 350 dd boat pushing down in back

Post by Olf Art »

JMO, but I think the gas tank needs to be at about the balance-center of the boat. That way, full or near empty the handling doesn't change. Batteries are a good choice for some weight shift because their weight is constant.

It may not sound like a lot, but if you move two 25# batteries from the transom more to the bow, you've taken that much weight off the transom and added it to the bow ..... the balance over-center doubles.

Same reason you move the battery in a drag car to the trunk. More traction = stronger launch.
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rost495
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Re: 350 dd boat pushing down in back

Post by rost495 »

I had batteries in a similar but longer hull... they were under the storage deck when we bought it. boat would not run dry... so we were told to move weight back, and that was super advice, little did I know the not running dry etc... was motor issues and that sunk us, I had moved the batteries pretty far back and now they are almost under the deck again... Probably should be under the deck, but I wanted the deck for storage...

Sounds like a good idea if possible. My boat sits and turns in deep water about like yours. THats why in deep water I only turn at an idle or on plane anymore. If on plane its a sweeping big turn. I prefer to keep the rudder minimal and bump the gas if i need a more agressive turn... not flooring, but just making it correct quicker.

Jeff

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SwampMatt
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Re: 350 dd boat pushing down in back

Post by SwampMatt »

Hey Bassinflats - you may want to watch that steering cable - it's VERY CLOSE to that muffler. That's not always a good thing to get hot unless you want to be replacing it every year. You've got a good possibility there to turn your rudders upside down and run the cable to the top. (your rudders are blank so it doesn't matter)

How many gallons is that tank? I've got a similar boat, and it looks like it's about twice the size of my 18-20ish gallon tank. That may be the issue right there.

Nice looking boat.

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Re: 350 dd boat pushing down in back

Post by One Eyed Gator »

Just went throught the same deal.My boat sat with the rear transom lip 2" from the water. To move around in the boat someone had to stand on the nose. When we were at the races on lake george. I notice that my boat sat deeper in the rear than most other boats except deckovers. It also took a long time to plain. Even with the motor so far back it ran on the nose.

I use my boat mainly for fishing in the gulf - 472 DD caddy on a 14' alumitech hull. I can not afford to sit as low as it was in the rear.

1st thing I forged the bottom flat. Tested it. Ran better, but still to low in the rear. I moved the rigging 1.75" forward (already had holes in the stingers), sat almost level in the water. Runs good but still pushed on the nose. I have raised the rear of the motor 1/4" (USED 1/4" POLY AND A HOLE SAW MAKES A NICE SPACER), ran better, still pushing a little. Added a second 1/4" spacers. Nose is freed up. I am going to add 1 more spacer, If it hops I'll know that is the limit and try washers to dial it in perfect.

It has taken some time but I am seeing the results and it is worth the time.

OEG

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Georgia Dawg
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Re: 350 dd boat pushing down in back

Post by Georgia Dawg »

bassinflats,I had a little 12'hull that sat lower then yours and I had to be careful getting off plane in deep water.Good luck or Bad luck it ever went down on me,I ran Peace River and the lake and it always did a great job.If your running where you can stay in shallow water try getting on plane in about three feet of water then move over close to the bank and try coming down off plane.I dont know how much stick time you've had so go easy at first and stay shallow.If that motor has the power and right prop it should get up and go,FYI my fuel tank was about in the middle or slightly forward of the rear operator seat.Look under my pic's it's the little green boat,that boat also had a SBC with a Gearbox on it before that,Best of luck and be safe!!!...... :D
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