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Pro Tunnel Race Boat Plans
Page Fourteen

Since I did not do the setup on the original Dillon Pro Tunnel, I have limited pictures of the details. Most of the pictures below are taken from my Dillon Pro Vee and Dillon Mini Vee.


Your steering system starts with a shaft and a pair of bearings. An aluminum shaft would be good lightweight choice; a stainless steel shaft will be corrosion resistant. However, all I've ever used is a 3/4" mild steel rod from the hardware store.

I get flange-type bearings from Surplus Center. Each of these bearing has two set screws so they can be locked to the steering shaft.

The exact placement of the wheel is a matter of what's comfortable to you. So climb into the boat and hold the wheel in front of you at a comfortable height.

I make my own steering drums from plywood circles. The larger circles are about six inches in diameter; the smaller ones about five inches. A large diameter drum like this makes for quick steering. My wheel rotates only a little more than a quarter turn in either direction.

Two pulley wheels are attached to the drum, bolted through with 1/4" bolts. These allow the drum to be locked to the steering shaft. 3.5" pulleys work best.

Coaming pulleys can be found at Glen L, Sorenson and Brown Tool and Machine. Also check eBay.

The Grant #334 steering wheel, 11.5" in diameter and lightly padded, seems perfect for this application. You can get them from eBay or Amazon or Summit Racing for about $25.

The trim buttons are mounted on the right side of the wheel; the ignition switch is on the left.

On the dash at left is the kill switch with lanyard -- required for racing, and a good idea in any case. Next to it is a regular kill switch, which is optional.

At upper right is the tachometer. In the center of the dash is the trim indicator (more about trim below). You might also consider a water pressure gauge; I've added one since this photo was taken.

Quick release steering wheel hubs are used on capsule-equipped racing boats where the driver needs to remove the wheel to get in or out of the cockpit. This capability is probably not necessary on the Pro Tunnel, but I only know of one other ready-made steering wheel hub on the market (see next item), and these work very nicely. And it is still handy to get the wheel out of the way once in a while.

The smaller part is fixed to the steering shaft. Drill a 1/4" hole through the part and the shaft and then insert a 1/4" roll pin.

The style at the bottom of the photo is probably best from the standpoint of quick removal to get out of a capsized boat.

Quick release hubs can often be found on eBay for about $20.

Another option is to use go kart steering parts, such as those available from The full kit comes with a 5/8" shaft. The Grant wheel mentioned above will not quite fit the three-bolt pattern on the go kart steering wheel hub, but it can be filed or re-drilled to work.

Or you can simply buy the go kart steering wheel made for this application, although I don't think you'll find it to be nearly as nice as the Grant 334.

These steering arms are made from 1/4" x 1" aluminum bar. They are bolted onto the back of the engine pan. I have always made my steering arms with a short brace extending from each arm to a powerhead bolt. But Jeff Larson, the owner of the original Pro Tunnel, came up with this arrangement -- so obvious that I kick myself for not coming up with it myself. The braces are bolted to the engine's steering yoke, using holes which are already there and already threaded.

You will want your cable attachment point almost directly opposite the tilt tube on the motor's clamp bracket. That way, as the engine is trimmed up and down, cable tension stays constant.

Although Jeff ran his steering cables directly through the steering arms, I prefer to use shackles (see photo inset). The shackle shown has a screw-in pin. I run a loop of wire through a hole in the top of the pin and around the shackle so that the pin can not unscrew itself due to engine vibration. That already happened to me once, luckily only during testing.


A foot-operated throttle is required for all OPC racing. Even if you are not going to race, I highly recommend it for your high performance boat.

The "Hot Foot" (available from various marine outlets) is probably the best known brand, but there are others. There's the "Hot Shot" from Bob's Machineshop. My Mini Vee had one called "Lead Foot." Look for one intended for use with your brand of motor. All these throttles use standard control cables.

They can be bought with an optional "slide plate" (seen here) which gives you a few inches of fore-and-aft adjustment.

Foot throttles are frequently up for bid on eBay.


For OPC pure stock classes, you must be able to shift your motor while sitting in your seat, with one hand on the steering wheel. I made this simple shifter for my Pro Vee. You can also use a standard unit from your motor's manufacturer.


If your motor already has hydraulic trim, then you're in business.

I set up my trim with an older Mercury cylinder and a Mercruiser pump. The bracket which holds the cylinder to the motor is homebuilt. The bracket at the forward end of the cylinder is part of my jackplate.

You will find more information regarding trim HERE.

You can find plans to build a jackplate HERE.

Fuel Tank and Battery

I use a standard three-gallon fuel tank and a garden tractor battery. Note both are tightly secured with ratchet straps.

Expect to use 1.5 to 2 gallons of fuel per race.

A garden tractor battery will easily provide all the juice you need for a weekend of racing, including several engine starts and almost constant use of trim. These batteries weigh about 17 lbs. If you are really pressed on weight, a motorcycle battery can be used -- about 10 lbs., I believe.

The battery on my boat is located against bulkhead #4. The trim pump (not shown) is against the inside face of the motorboard. The fuel tank is in between. There is nothing sacred about this arrangement; yours may vary.

Battery Switch

At a race in 2007, while working on my Dillon Mini tunnel boat in the pits, one of the steel-jacketed trim hoses came in contact with the trim pump solenoids. With no quick way to cut the juice, I had to pull this HOT hose clear with my hand.

The hose was ruined, and the boat had to sit out the next race. But more important, there was the distinct possibility of fire, so I consider myself lucky.

With this incident in mind, I now but a battery switch in all my boats. It is easily accessable in an emergency, and is handy for cutting off the juice when trailering, or working on the rig. This switch spends most of its time in the OFF position.

A word about motor height.

On a typical fishing boat, the motor's cavitation plate is about even with the bottom of the boat, or up to an inch below the bottom.

Motors on racing boats are mounted much higher. As counterintuitive as it sounds, the idea is to get as much of the prop (or at least the gearcase) out of the water as possible.

On one of my v-bottom boats, mounting a 15-inch motor on a 20-inch motorboard is just about right. Performance-wise, you could go even higher, but will no longer be pumping cooling water, and I'm told that can be a problem.

On a tunnelboat, however, you can generally jack your motor up as high as performance dictates, to the point where the entire "bullet" is actually above the deepest part of the boat. There will still be plenty of spray coming through the tunnel to feed the cooling water intake, and you will have reduced engine drag to the barest minimum.

One caveat: If you wish to take advantage of this sort of engine setup on your tunnelboat, you may need hydraulic trim. Without the ability to trim your engine down, pushing your prop deeper into the water, and directing thrust downward somewhat, you may have difficulty getting your boat on plane.

Another caveat: As soon as you jack your engine much above the fishing boat setup, you will need a prop that has been "cupped" on the trailing edges.

Cup, a slight curl at the edge of the blade, increases the grip a prop gets on the water, and is essential in any situation where the blades are piercing the water surface.

Any prop shop should be able to cup your propeller. Many props come from the factory already cupped.

A good source for racing props is Ron Hill from California, USA. See him on ebay:

Let's race!

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