Outfitting a River Jet Sled

There is a great difference in outfitting a jet sled for shinny water of a small to medium size river as compared to just having a jet unit because it was on the boat when you bought it or you think it will come in handy some day IF you get into shallow water.    My definition of skinny water is anything that is less than 16″ deep.  This may be generous, as some times if you run small fast flowing rivers, you will have rocks and riffles whereby you need to negotiate between the rocks and hope to not blink at the wrong instant.

Most of these combo boats will have forward mounted steering with windshields and a convertible top.  It would be very unusual to see one of these boats made of anything other than aluminum.

I would recommend that you ride with someone who has experience at this a few times before you try it on your own.  Ask many questions on how to read the water.   You will need to know what to look for as to boils (behind submerged rocks), slots where water is fast between rocks on a riffle or gravel bars.  How to read tail-outs above riffles is another important item so you know where the slot will be if you are going downstream. 

And when you do get enough guts to tackle it on your own, do not run it with a new boat.  But buy a used boat as your first jet sled.  You WILL run aground, into or onto rocks.   Many times these rocks are rather hungry and can take large bites or at least dent the heck out of a aluminum boat.   And they also seem to prefer bright shiny new boats.

You will see boats in this category from 14′ to 22′ long, and powered from 40hp to 250hp.

You can tell these are jets by simply watching as they go by at full power.  The outlet water from the jet pump, being near the surface, will throw a large thrust of water into a rooster-tail for a considerable distance behind the boat as compared to a standard prop driven boat.

Jet Boats, Normal :  Basically these boats use a large hydraulic water pump attached directly to the motor’s driveshaft.  The large jet of water is directed rearward and the steering/turning is accomplished the same as a regular prop unit by twisting the motor/out-drive so the water jet pushes the boat in the direction opposite the flow.  They have an large (7″ square) water suction intake grill mounted just under water at the stern.  The grills in the intake are to prevent rocks when in shallow water and debris from being sucked into the impeller.  The exhaust gasses are exhausted out the center of the water jet output.

These are usually outboard jets as described above, however you will see some inboard versions used on some sections of water.  They are usually used where the operator may have reason to believe he will be operating in shallow water where a propeller driven boat would have trouble navigating.   These boats are normally nearly flat bottoms (very slight Vee) and with the water intake so high, the boats at full power can run in about 6″ of water.   They are a stable boat, but do not handle a lot of rough ocean type water well.  Then since the efficiency of these of these jet motors is decreased 30%, fuel economy is not that great if you intend to travel any distance.

 About the smallest hp you will see for an average jet boat will be 70hp, as you loose about 30% power over the same propeller motor.  Some smaller lightweight aluminum boats (14′) where only one person will be fishing, may use a 40hp motor.

One bad thing about jet boats is that since the jet pump is mounted directly to the driveshaft, the impeller is turning all the time the motor is running.  Forward / reverse is accomplished by a clamshell that is pivoted on the rear of the jet’s output nozzle.  For reverse, this clamshell pivots up, diverting the water forward.  There is really no neutral, except somewhere about 1/2 way between forward and reverse, you can possibly find a position where there may be enough water being diverted both forward and reverse creating a false neutral.   Many when starting and warming up the motors of the jets will ground the bow into the bank or stay tied to the dock and try to find as close a neutral as possible.

The newer units (last 20 years) have a slotted plate mounted to the clamshell shaft that locks the clamshell into position when under full power.  Without this plate, you may loose power as you increase boat speed.  The reason is that under full power the clamshell needs to be snapped into position, locking it against the under side of the jet nozzle.  If your cable linkage is not set right to accomplish this, the clamshell will be forced rearward somewhat by the force of the water hitting it, pushing it into a partial reverse mode.  This is somewhat counterproductive to full forward force of the jet’s efforts.

Another bad thing is that these jets are susceptible to sucking floating grass or weeds into the impeller, making the motor useless by blocking the water intake to the impeller until the debris is cleaned out.  Therefore the motor really needs to have power tilt so the unit can be raised enough for the operator to be able to clean the grates.  On the inboard jets some manufacturers make a built in “stomp grate” to clear blockages like mentioned above.

The majority of these jets however will normally never be used in shallow enough water to really warrant the jet drive, just as a precaution more than anything.  If they are used in skinny fishing water mentioned below, the operator is handicapped in that he is just that, the operator, and usually does not have the time to fish as he is busy making the boat go where it needs to go to catch fish in a fast moving river, yet be able to pull the kicker motor up at the same time fire up the jet to keep the boat from being swept under a log or stranded on a shallow tail out riffle.  If he does get a chance to wet a line while side drifting, chances are while he is trying to maneuver the boat to but his buddies in a better position, he may get his line snagged and with that comes the very good chance to break a rod (been there-done that).

Since there is no neutral on these jets, and most motors need to initially warm up when first started, there becomes a problem if you launch in swift water and need power immediately.  One thing many of these river jet owners do is to leave the boat on the trailer when they launch, as most of the river launches do not have docks, so the procedure is to start the motor and (in neutral or as close as they can get), let it warm up, then unhook the safety chain, then back the boat out into the current.

They also can have problems on reloading onto the trailer.  Again because there is no neutral, and reverse is not that efficient at low speed, it does little good to shift from forward to neutral just to let it coast onto the trailer.  Also since there is no rudder in the water, if the wind is blowing, the boat most times, does not go where the operator is trying for.  So, on many of these jet boat trailers, you will see, side guides inside the fenders similar to the one in the photo on the left below.  These allow the operator to nose the boat onto the rear part of the trailer, apply power, then with the boat’s bow acting as a pivot against one of the guides, the operator can then apply power, pivot the motor so it will now be guided onto the trailer.

Most all jet boats will use a trailer that has bunks instead of roller glides.  Part of this is that 99% of the jet boats will be aluminum where roller glides over time may put more pressure in centralized locations possibly denting the hull if it gets to bouncing or hauled over rough roads.

Most of these style boats will use the Columbia River rocker anchor and float puller system because they normally use these boats on larger rivers.

19′ Alumaweld with 150 Mercury jet Willie Predator with typical motor sizes & arrangement

Jet Boats, Skinny Water Versions ;  Everything mentioned above will also pertain the following type of boats, basically the means of steering is different.   But also they very seldom have any windshield, as this takes up room in the boat and with the operation of the motors at the rear, the need for protection is not needed, (these skippers are hardy souls and know what raingear is).

One thing to remember on fast flowing and possible intermittent shallow water, is that going upstream is no problem as if you are uncertain of what is coming up, just slow down, hold your position and observe where you may need to be traveling.  But going downstream, in order to maintain steerage, you have to be going faster than the current is.  This can get exciting, even possibly dangerous if the operator does not read the water correctly.  Therefore for a newbie, it is best to launch so that you can run upriver in the stretch of water you intend to travel/fish, so you at least have some idea of what’s ahead when you return downstream to take out.

A standard rule of the road is that downstream moving boats have the right of way because this lack of maneuverability.

It will take some trial and error on your part before you get accustomed to your boat AND the river you are trying to navigate.  And each river will have it’s own style of water.  Remember that jet outdrives are not efficient at low RPM, but need to be reved up considerably more than a prop unit to be effective in a current, so DON’T baby the throttle.  Another thing, since most of these skinny water jets are tiller operated they are very sensitive to very little steerage movement if up on a plane, so use the lanyard kill cord.

IF you get in REAL skinny water try to keep the boat moving, as if you have to stop, your boat will settle down in the water and the jet intake will be CLOSE to the bottom and as most of these bottoms are known to be covered with lots of rocks.  If it is running in this shallow water, your chances of sucking rocks into the impeller just went up 1000%.  Small rocks may be sucked thru and out with the exhaust water.  But chances are they will also chew up the leading edge of the aluminum jet impeller, decreasing the efficiency.  Larger rocks and sticks may get lodged in the intake grating thereby lowering the suction efficiency until they are removed.  This will also be applicable if you beach the boat on a sand or gravel bar.  You may need to push the boat into deeper water before trying to start the motor.

You will see 2 set-ups for this type of fishing, (1) tiller steering, (2) center console steering located nearer the stern.

These skinny water jet boats were probably perfected by river fishing guides in the Pacific Northwest.  The bulk of them will have tiller mounted motor units even up to 200hp.  This arrangement gives the guide more immediate control in navigating a fast flowing river.  It also puts the guide in a position where he can observe all of his clients lines at all times, by being at the rear of the boat and facing forward watching them the bulk of the time.  

Another thing is that when in tiller operation, the motor will usually need to be tilted down deeper in the water on the rear, to help compensate for the different weight distribution nearer the stern in order to get it up on a plane faster.

Those of us who intend to fish this type of water may well take a close look at how these boats are set up.  Because if your jet has forward steering and controls, when you are side drifting or backtrolling, (doing controlled slipping downstream) WHEN the water gets shallow then things start happening very rapidly, and you will need to start that main motor ASAP.  If you are using a kicker motor and have to pick it up, then have to run to the forward controls to start the main motor, it may be too late and you are on a gravel bar or sucked under a log.   Therefore when using the forward controlled sleds, the skipper is just that and not really also a fisherman.  But when using tiller controlled motors, he has more of a chance to get at least some fishing in.

These boats are normally nearly flat bottoms (if a Vee bottom, very slight at 12 degrees) and with the jet water intake so high, like even with the bottom of the boat, the boats at full power can run in about 6″ of water (not recommended, but possible for a short distance).  The reason I say not recommended, is that at that water depth, you have to be moving rather rapidly because if you slow down, the boat will come off a plane and will then settle deeper in the water.  And if it is gravel bottom, if you stay in one position for more than a few seconds, the jet intake will suck rocks up against the grate and possibly into the impeller.  This may well create some blockage in the impeller which will slow you down CONSIDERABLY until you remove them.  And on a fast moving river, this can prove dangerous.

About the smallest hp jet motor you will see for an average 16′ jet boat will be 70hp, as you loose about 30% efficiency over the same propeller driven motor.  Some smaller lightweight 14′ aluminum boats where only one person will be fishing, may go down to a 40hp motor. 

As for brands of outboard motors, you will see most of the popular ones, it just depends on the boat dealer and what brand he sells.  However for new motors, Mercury and Yamaha seem to be the most favored with Honda and Evinrude coming into the picture also.  There is one company that pretty well has this market cornered, Outboard Specialists, which builds these jet units and make them to fit all brands and models of outboard motors.

These boats will also usually have a kicker motor with a hydraulic tilt,  the commonly accepted is the Yamaha T8, which is a 8 hp 4 stroke high thrust unit.  The guides may also have mounted a heavy duty 24 volt electric trolling motor for usage where minimal power is required to stay in a position if hovering over a deep hole or sliding downstream under power as in backbouncing.

These boats if relatively new, will usually have full length rod lockers in the gunnels and numerous movable rod holders.  The sonar units will be mounted at the rear.   Most will have a movable swivel seat for the operator.  The guide boat in the photo below on the left has 2 movable seats in the rear with 2 stationary seats in the front.  Under the front seats are waterproof storage.  A fish-box is located in the forward platform section.  The fuel tank is under the floor, with the battery tucked in under the transom shelf, making a very clean deck layout.

The boat in the photo on the right is an older (1979) 16′ Hewescraft, riveted aluminum boat has been outfitted as a river boat.  Note the tiller handle operation on the 70hp Johnson main (jet) motor.  Also note the electric start 9.9 Johnson trolling motor and a 12 volt electric trolling motor on the opposite side of the transom.  This unit uses 2 batteries, one for the main motor and the other for both of the trolling motors. 

The sonar is visible in the lower LH corner of the photo.  The main motor’s 12 gallon fuel tank is under the Port rear bench seat.  The 3 gallon fuel tank is for the kicker motor.  The padded folding seat is a swivel seat from Wal-Mart and is movable.

Break time for a 22′ Guide boat, with tiller mounted 150 hp
outboard jet
A old 16′ aluminum jet boat set up for river running

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