Do tunnel hulls really work with outboards?

[ducktrooper]

I'm looking at a 1642 Weldbilt with 25 hp ss merc. The boat has a tunnel hull.Will that help me go shallower at various speeds as I do flyfish on some skinny rivers? Will I need a jack plate to get prop to perform most efficiently? Thanks.

 

[Paul Marx]

Yes and no . the boat will sit a little bit lower due to the displacement changing . you can mount the motor higher (up in the tunnel) which will give you less of the lower unit below the bottom. If you put some sponsons on the back it will make up for any displacement loss . They will also help you plane out much faster by keeping the bow down.

 

[ducktrooper]

Thanks Paul...I suppose I need a jackplate of sorts, either manual or hydraulic. I've read that you don't want any/much setback with the JP in order to keep the prop as close to the tunnel as possible...is this correct?

I might consider adding trim tabs in lieu of sponsons on back.....any thoughts on one versus the other? Thanks...

 

[Paul Marx]

Remember if it's a tiller you don't want to set it back to far. Now don't hold me to this , but i read some years ago that for every inch of setback you can raise the motor 5/8" . Here in Texas we see a lot of boats designed to run the vast flats in search of Redfish. With enough setback you can lift (via J.P.) the lower unit up to where hardly anything is below the bottom line of the boat. You can get by with setback plate and an anticavitation plate to help hold the water around your prop. Every boat I own has a water pressure gauge on it.

 

[Paul Marx]

I forgot . With a J.P. you have infinite adjustment for fine tuning or if you get in a chop and start to cavitite you can lower it on the spot. Hydralic units are nice , but you can get by with a manuael one and say $$$$$$$.

 

[Lowe 2070 CC]

I might consider adding trim tabs in lieu of sponsons on back.....any thoughts on one versus the other? Thanks...

The sponsons primary purpose is to replace or increase the flotation lost due to the hull displacent decreasing when the tunnel is cut out. They do lengthen the planing surface and allow for great shallow water running, at the cost of some top end speed and the tunnel/sponsons don't lend themselves to operation in reverse. The Texas coast guys have really perfected the shallow water tunnel/sponsons/jack plate/anti cav plate like no one else.

Trim tabs don't really come into full effect until you are on plane, they also lengthen the planing surface but there real benefit is their ability to level and adjust the ride attitude of the boat.

 

[ducktrooper]

Hey Lowe....thanks a bunch for that info. Aren't many of those guys with sponsons running mud motors thru super skinny water? I don't want to lose reverse capability but might consider adding if not too expensive to have someone build and weld on.

Trim tabs would be used for getting on plane at lower speeds like when I'm scouting for fish in skinny water.

 

[RiverBottomOutdoors]

Should also point out that tunnel hulls come in 2 types. Tunnels for props and tunnels for jets.

 

[Lowe 2070 CC]

I know a lot of folks running mud motors with sponsons/beavertails, through places where I can't even see water just muddy crawfish ponds to get to their duck hole/trapline.

Then there are the guys running props with sponson/jackplate/anticav plates in 6" of water fishing the flats. two different set-ups, but both rely on the sponsons for the extra flotation they provide. 200 lbs of flotation can offset a bigger motor, a poling platform, or lessen your draft 2" with your existing motor.

Sponsons provide that benefit while sitting still. Trim tabs do nothing unless you are running.

 

[Ictalurus]

You around Memphis? Think I saw this one on Craiglist. Looks a little high priced to me, you can get a lot more for $3500 than a 1642 w/ a 25 HP.

 

[ducktrooper]

that's the one I'm considering but it's 2 hours away and price does some kind of high considering hull is 15 years old....layout is nice though. the other thing I worry about is hull thickness....seller doesn't know what gauge it is. I don't plan on jumping stumps..mostly will use for fly fishing on tailwater rivers and some duckhunting.

 

[JMichael]

That's a poor group of pictures of it. Can't really tell much about the condition of any of it although it looks like it has cheap plastic seats. Does seem to be a bit over priced. It would be interesting to see how well that tunnel hull performed though.