Boat porpoise problem
 

I have a 1750 aluminum boat with a 40 Tohatsu and it porpoises really bad unless I have it trimed all the way down. I can lower the motor on the transom one notch. Will that help or do I need to get some trim tabs or a hydrofoil?

Lowering motor will make it porpoise more...trim tabs or a jackplate would help

Trim tabs....hydrofoil creates drag and will slow you down.

I used to have a 50 Yamaha on a 16' Carolina Skiff. I had a heck of a time with it porposing. I installed a jack plate and fought it for months finally i I added a hydro foil and it was night and day. I could control my bow like it was on hydraulics when on plane. Made all the difference for me.

Get a rubber maul and put u a little hook in the bottom of your boat in front of the transom. Do little bit at a time until it stops bouncing when u trim it up

:eek:

Trim tabs create drag also and slows you down

Cool

Adjust your load, fuel tank, battery. Something like that. Then try trimtabs but putting a hook in a boat goes against everything I have learn about boats in the last 20 years. We have knocked out hooks in hulls and and fixed the problem. I would redistribute the load first.
Do you agree Montauk17? A friend of mine said you know a little something about boats.

redistribute the load then try lowering a notch if that doesn't work. Think about it you got to trim all the way down, when you trim up the boat porpoises, you need more motor in the water to keep that from happening.

I never heard of anybody beating a hook on the bottom. But hey,you learn something everyday. Small aluminum tabs welded on the bottom always works for me. I had a 1448 alweld with a battery and 6 gal tank in the back. Could run with two people sitting on the back without any issues with these type of tabs.

http://i68.photobucket.com/albums/i3...1/IMG_0647.jpg

A perfectly straight bottom boat will not run above 30mph without bouncing. First step is to adjust the weight in the boat. if that doesn't stop the bounce next step depends on how much you want to spend. A lower rake prop will help, rake causes bow lift, a expensive attempt that may not work completely.
If you have never heard of a hook in the bottom of a boat, you need to look at the bottom of most hi-perf boats. We have been hooking boats for 30 years. The difference in a small hook and trim tabs is the length of the angle. Trim tabs are usually 6" long behind the boat. That small area requires a steep angle to accomplish the work. A gentle hook in the bottom starting that the back of the rear seat and ending at the transom gives you a much longer area to accomplish the same thing, no speed loss, no gathering vegetation in reverse. Like I said, been doing it for 30+ years, never slowed one down yet. Ask anyone that has purchased my hulls after I'm done with them. Ask anyone that has seen my rigs run. Better yet, here's the boat I currently own, guess what, it has a hook at the rear of the hull on the bottom. 4 stroke 40 merc with a 60 pcm in it.
I would start with a 1/8" hook and add 1/8th at a time until you can trim about 2 degrees positive with a normal load. The most I have ever hooked is 1/4". Hook only the two outside corrugations, DO NOT HOOK IT IN FRONT OF THE MOTOR!
Here's a video of the boat in the pic with the hook running black bayou:
same old 1552 WeldBilt and exact same old Merc.
http://i126.photobucket.com/albums/p...US1/Hook-1.jpg

I stand corrected.

We're all here to learn and share:D I try to use the most cost effective ways to accomplish things, you know what they say "po folks got po ways".
D

CajunChristian hooked my boat. And it was night and day.

In the interest of learning......

How do you "Hook" the bottom of an aluminum boat like shown in the picture holding the tap measure? I am thinking maybe using a big hammer [sledge hammer???] but think that would probably not look good after a few good hits.

Do you have to put the boat in some kind of big "press" to make the bend in the bottom?


I once tried putting a 15 hp outboard on my 12' Alumacraft boat that is rated for 8 hp max. Just me and the engine, no other weight. I don't know how fast I was going, but once that boat planed out, it felt like it was "dancing" on the smooth water. I don't remember if I tried running WOT, but for me that was too much hp for that 12' boat and did not feel safe.

\
I use a 12" piece of 2X4 and a loaded rubber hammer. It takes much less blow than you think. I measure with a straight edge constantly to insure a smooth curvature. I usually just slide the boat back about 2' on the tail end of the trailer, lay on my back and tap away. About 10 minutes to completely hook both sides.
You want your boat to sit up on the tail and run, but, you don't want to use all available horsepower to lift the bow.
Stop this video at 2 seconds and notice the trim angle of the engine and how much boat is out of the water.
Less boat in the water=less drag. Less trim angle=less wasted horsepower. You have, let's say 50hp, how much will you use to lift the bow and how much to push forward? That is what makes our tunnel race boats so fast, air flys the boat and the motor only pushes forward.
Notice the trim angle on this race boat, and notice how much boat is out of the water:

The ways to control the bow on a loaded aluminum boat is:
weigh the bow down, not practical
trim the engine all the way down, a tremendous waste of horsepower
trim tabs, takes speed away, angle too sharp
hook the rear bottom of the hull, no speed loss

Cajunchristian also hooked my boat and it runs great. I have welded trim tabs on my 1648 and it's like dragging a plow through the water. Way too much drag.

To each their own....I rather weld tabs on than beat on the running surface of a boat with a hammer. On the flat I had there was no loss of speed. Took some time to get the angle right but once it was right it was all good. But I never cared to do over 30mph with a tiller steer flat anyways...

Spunt Drag u talking about the small welded tabs like the ones that come on an Alweld or in the pic above?
I dunno if I could handle putting a hook in my brand new hull or if it would actually help, but I don't have porpoising problems either...

If it ain't broke, don't fix it:D
D

Yep, it's a 1648 Alweld wit those small welded aluminum trim tabs. They're useless. They'll stop the boat from porpoising but it's like draggin a lead sled. I don't know why it freaks people out so bad to put a hook in their hull. Like CajunChristian said, look under most new bass boats or any high performance boats. If I didn't have a porpoising problem then I wouldn't hook it, but for those that have a porpoising problem and want to maximize their performance, HOOK THE HULL!

The answer to the question is easy lol, hook the hull. If you want the best performance out of a tiller on aluminum, you dont lower the motor and install trim tabs. This aint yankee land geez where are yall from lol!

I have 17' aluminum v with a 3 degree v in the back. I have a 40 yamaha pushing it, but I have a bad porpoising problem unless I put every ounce of gear on the bow. Does the hook work on boats that carry their v all the way to the back?

Sure does.
D

Thanks for the information, it may come in handy some day.

I also have a 16' Alumacraft with a 40 hp Tohatsu [restrictor taken out]. It will run 36 mph at 5750 rpm with the engine trimmed up about 1/3 of the way [on the trim gauge] before it starts to bounce. I probably have too much weight in the back [3 batteries, charger, and 9 gal. gas] to make it run any better.

I get about 35 mph and 5700 rpm with a little heavier load, so I am ok with the performance.

U would get better performance if u put some hook in the hull.

These work for me... Heavy 1652, Four Stroke 40 with trim, 8 gallons of gas, two batteries and my big arse in the back.... Jumps on step, the faster you go the less pitch is in the tabs. WOT they are pretty much even with the bottom of the boat...

I have had them going on two years and put them thru a couple of groundings at Toledo when the water was low, stumps on the river, etc...

Good luck :D

You doing it all wrong bro take them tabs off and start beating. :work:

At least somebody learned something on this dumba$$ thread

Yep,I learned west siders strum to a different tune. :shaking:

And I learned there is some serious cluelessness on dis forum

Is that Lake Chuck Duck?^^^

Kids driving around with trim tabs and whale tails goin 30 mph. Feesherman nailed it wit the cluelessness comment lol. Dont wanna love tap a boat but youll weld two anchors on it. Tapout already.

I've done the hook in my other boat I had and it made a difference. I definitely believe on putting a hook in it verses some of the other methods.

Yea like a national racing championship tune.


Holy $hit! Somebody wit some sense!

Lol

Only reason I welded tabs on my 1448 is so I could run with two people sitting on the back with a gas tank and battery. Before I put the tabs it would run 28mph with just me in the boat. After the tabs it would do 30mph with two people sitting on the back. This is with a 25 merc 2 stroke. If you want to bang on the bottom of your boat have at it. Tabs were a benefit for me so I was happy. If you want speed get a bullet or allison.

Finally!!!!

Not me but Cajun Christian banged on mine so good I'll let him bang on every one of mine from here on out. In fact, I'll let him bang on it straight off da new boat lot.

Whatever floats your boat. :rolleyes:

Nice!

I tried hooking my hull but being fiberglass it didn't work out to well.... :eek: Joke
I run a 15' marshrunner with a 40 merc. Run trim tabs kinda like hydro has shown. Removed the hydraulic shocks and put stainless turnbuckles. Run them about 1/8" below bottom. Performs great for me. Hops on top quick and run 52mph wot.

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Marshrunner u run that white one with the platform? Were you at Prien launch sunday?

Well I don't have porpoise problems so I will stay out of the crossfire. What I will say is that, if you run an aluminum flat or modified v in south La. and you're hull isn't beat up at the bottom anyway, you're doing it all wrong.

Nope, run an old brown one. Getting old and beat up but still letting me catch fish lol.

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:eek:

Ha good point.

I have the completely opposite problem. Boat will not porpoise, I just can't get any bow lift at all.