Ott DeFoe's river boat

[Basfis]

The tunnel on that rig is supplying water to the lower unit. Stacked jack plates count on the crest of the forced water to have something usable by the prop. There is a deflector in the tunnel too. 

I’m sure it’s undesirable to have the motor that high and the tunnel wide open for any length of time. 

[fishinwrench]

3 hours ago, dblades said:

 You may have a  14" minimum but they are running in 3" with a prop rig.  Guess they didn't hear you say tunnel hulls suck at shallow running. 

3" my bald headed @$$

 

Do you realize that the skeg is 9-10" below the propshaft?

Once the very top edge of the prop clears the water (at about 11.5" on a 3cyl motor) your RPM's are gonna go wildcat.

Let's not forget that the water intake is slightly above THAT.  

Think about what you're saying.

A tunnel hull doesn't turn 3" of water into 14+".  

[Champ188]

I thought the same thing at first but my understanding is that somehow that tunnel is "building" a column of water for the prop to run in that is actually above the surface of the river. 

[fishinwrench]

1 minute ago, Champ188 said:

I thought the same thing at first but my understanding is that somehow that tunnel is "building" a column of water for the prop to run in that is actually above the surface of the river. 

Yeah maybe 4 inches.....if you have 12+ inches of water to work with. But you still have a lower footprint with the tunnel in order to create that displacement.     The same effect can be gotten by extending the motor 2' off the transom with a flat bottom boat, but you still have to have enough UNDISTURBED water to cover the skeg, prop, and water intake.   

There's nothing on this Earth (the size of a boat) that you can pull through 3" of water that will turn it into 14" of reasonably undisturbed water. 

Even the shallowest of riffles have 3" of water.   C'mon now.  

[nomolites]

I read an article about that rig and the builder right after that tournament; sounded to me like he was running it just like the jet boys do; get a head of steam up,  plane out and then coast through the really skinny patches and then hammer again when you have bite.  He had very little tackle/gear on board to minimize weight - the rig was super light so he was as high in the water as possible.  I think that should be a legal gamble if a guy wants to make it; he is sacrificing performance in every other way.  Just my $.02.

Mike

[fishinwrench]

The water pump on a prop gearcase needs to be primed, which means that it can't "suck up water" until it has been started with the pump housing completely submerged.   If you run so shallow that it looses it's prime (even for a split second) then the only way to get water pressure back is to set the motor down in enough water to once again prime the pump.   Keep in mind that the pump is 4-6" ABOVE the cavitation plate.    Low water intakes allow running the gearcase higher BUT not without first starting with the water pump housing completely submerged.    

So even if you could run through 3" of water (which you can't) you ain't gonna do it for long without melting a piston.

[fshndoug]

I think some these pros blow a lot of smoke.3 inches my butt

[grizwilson]

4 minutes ago, fishinwrench said:

The water pump on a prop gearcase needs to be primed, which means that it can't "suck up water" until it has been started with the pump housing completely submerged.   If you run so shallow that it looses it's prime (even for a split second) then the only way to get water pressure back is to set the motor down in enough water to once again prime the pump.   Keep in mind that the pump is 4-6" ABOVE the cavitation plate.    Low water intakes allow running the gearcase higher BUT not without first starting with the water pump housing completely submerged.    

So even if you could run through 3" of water (which you can't) you ain't gonna do it for long without melting a piston.

 

1 minute ago, fshndoug said:

I think some these pros blow a lot of smoke.3 inches my butt

Don't you two know everything in Bassmaster is true, besides it's even on the internet so it has to be true..... wonder who measured the water depth for them? 

[fishinwrench]

Here ya go.   It takes 23" at a minimum to prime the pump. 

 

and 16-17" to maintain water pressure.

 

Add 2-3" to THAT in order to keep the prop from blowing out. 

 

This is on a 3 cylinder outboard.

[Mitch f]

If they have somehow taken away the negatives of the tunnel hull design and turned it into a net positive, then by all means,  that’s a good thing. 

But I kind of doubt it.