Knowing the draft of your boat on plane??

[TommyBass]

Hello All!

I was wondering if any of you have any experience in figuring out how shallow is too shallow when running your boat on plane (that is without destroying it  ).  I recently traded my fiberglass bassboat in for a tunnel hull 18ft john boat with a 4stroke 90hp.  Has a jack plate and floatation pods, basically designed for "skinny" water.   But I dont know how skinny is skinny and am too afraid to open it up and get on plane in shallow water without having some clue.

[Wayne P.]

Did you get the 90HP jet or a 90HP prop motor?

[cart7t]

The key words here are "without destroying it"

;D

This is a low water dam on the Big River at Cedar Hill Missouri. The dam at one time held back water for use in the mill you see in the background. The dam was breeched years ago in a flood. There is a 2-3 foot drop between the river below and the dammed pond above. The breeched area (whitewater you see in the middle of the picture) is full of broken up chunk boulders.

My buddy regularly ran that breech with his 18 1/2 johnboat with 85hp Johnson with Jet drive. The first time he did it when I was in the boat I about cr*pped my pants as we approached it. After bouncing off several boulders we got through.

I wouldn't recommend it though. That fits the description of a shallow area that could destroy your boat.

[The Next KVD]

If you have a jet powered outboard than I have heard of guyz driving them in as shallow as 4in. but i'd be skeptical.  MOre like 8-10in.  Prop driven outboards i would say it'll depend on the boat and if it has a jackplate or not.  I don't drive my Nitro on plane when the water is less than 2ft.  I had a bad experince one time w/ shallow water and took out a lower unit. :'( thank god for insurance though ;D

[Way2slow]

If you have a hydraulic jack plate and water pressure guage, with the right prop, depending on the tunnel design, you could probably buzz right on through 4" of water.  You can actually run your outboard in shallower water than a jet is recommend.  Jet drives go through like a vaccum cleaner a suck all kinds of crap up off the bottom, creating major wear problems.  Jets are great for running rivers and such where there are lots of trees, logs, etc you have to go over because there's nothing below the hull, but not good for running shallow flats.  Your problem is getting on plane in shallow water.  You will probably need eight inches or so to get it up on plane without dragging the LU.

My soon 20' back bay glass tunnel hull will run in 3" with a 175 Etec.

[BrianinMD]

Tommybass mentioned flotation pods, never really checked them out before. How much stability, if any, would they add?

[TommyBass]

Sorry, I failed to mention it was a prop drive. I do have a jack plate installed, but just the manual type, not hydraulic. The boat is a G3 1860CCT. I do not currenlty have a water pressure guage, would that be worth my effort and what do I look for for a "good" reading? Also, would you all recommend a stainless prop for if I do hit something rather then the tin foil aluminum one it came with?

O, and I about forgot, it does seem that the two pods in the back do add  quite a bit of extra floatation for stability and resisting rear end sink on whole shot.

Thanks for the responses so far!

[Catt]

If you have a hydraulic jack plate and water pressure guage, with the right prop, depending on the tunnel design, you could probably buzz right on through 4" of water. You can actually run your outboard in shallower water than a jet is recommend. Jet drives go through like a vaccum cleaner a suck all kinds of crap up off the bottom, creating major wear problems. Jets are great for running rivers and such where there are lots of trees, logs, etc you have to go over because there's nothing below the hull, but not good for running shallow flats. Your problem is getting on plane in shallow water. You will probably need eight inches or so to get it up on plane without dragging the LU.

My soon 20' back bay glass tunnel hull will run in 3" with a 175 Etec.

X2  

[CFFF 1.5]

Not sure why but I always heard that running in shallow water you should use an aluminum prop. I used to run Mosquito Lagoon a lot and we always had an aluminum prop. Also if you need to plane in shallower water turn to one side real hard when you go to wot, it will help you get up faster. We used to run our boat in less than a foot water and would sometimes run a ground but never got any damage thankfully.

[Wayne P.]

CFFF 1.5, the aluminum prop suggestion regards the replacement/repair cost difference between the aluminum and stainless prop when (not if) you destroy it running in shallow water.

[CFFF 1.5]

My only thought was that possibly the softer metal would bend more easily when it hits something so as to maybe not break things inside the engine.

[surfer]

My only thought was that possibly the softer metal would bend more easily when it hits something so as to maybe not break things inside the engine.

x2  

I shattered my reverse gear with a stainless prop.  The prop held up fine, but the whole lower unit had to be replaced to fix the reverse gear (cheaper than the gear and labor).   An aluminum prop would have been torn up, but saved the gears.

[TommyBass]

Don't they make a "bushing" of sorts now for these props that take the beating when you hit something.  I think it basically just strips it out when you hit something hard, then you just have to buy a new insert instead of a prop.  All I know is Ive already hit a little rocky sand with the aluminum and put several dings in it with only a few hrs of run time.

[Way2slow]

The spline inside the prop is moulded into a rubber bushing and then the whole assembly is pressed into the prop.   Yes, is "suppose" to slip inside the prop on impact with something but there are times the gears or prop shaft do give way before the bushing slips.   The ideas is the aluminum prop is so much more fragile than the stainless prop is that it will brend/brake much sooner/easier than a stainless and hopefully save the actual lower unit from damage.  Then there's the fact that a $150 aluminum prop will run you $400 or more in stainless.  

Now, with all that said, the only thing I ever run an aluminum prop on is my 4 and 9.9 because the only time I run them is when in small rivers jumping logs, limbs and all kinds of junk where they are constantly getting beat to hell.  Everything else has stainless props.  They grealy out perform aluminum props in all aspects, take abuse much better, can easily be tapped back in shape if you ding an edge and don't get knocked out of shape no where near as easy.  

If you really want to get the most of any high horse powered bass boat, you send your $500+ stainless prop off and pay another $300+ to have it tuned for your boat.