Tag Archive: 4 hp

How much HP for my S4 skiff’s outboard motor?

This article summarizes research performed by Captain Larry Jarboe, as well as inputs from Wavewalk dealers and S4 clients. Its purpose is to answer a frequently asked question (FAQ) from prospecting clients, which is “What outboard motor should I choose for my S4?”

The answer is that the outboard motor you should choose for your S4 depends on two factors, which are

  1. How much power you need
  2. How important is the motor’s weight for you

And there is a trade-off between power and weight, namely that the more powerful the motor, the heavier it is, and the harder it could be to carry it.
In any case, the motor should be a 20″ log shaft (L) model, and not a 15″ short shaft (S) model.

2 HP outboards

Outboard motors in this class weigh around 30 lbs, which makes them fully portable even for a user who’s not very strong. A 2 HP motor can propel an S4 skiff with one person on board at speeds up 8 mph, even in choppy water. This speed would decrease as the boat is required to carry more passengers on board. S4 owners who tested such motors with their S4 skiff reported that the boat felt under powered, which means that they felt like going faster, but the motor lacked the powered required for this. For this reason 2 HP motors are not popular with S4 users. Another reason for their lack of popularity is the fact that being air cooled makes them noisier than water cooled motors.

3.5 HP outboards

Outboard motors in this class weigh around 40 lbs, which makes them still portable, but less so than 2 HP motors. A 3.5 HP motor can propel an S4 skiff with one person on board at speeds up 14 mph, even in choppy water, and it can propel the boat at 12 mph with three passengers on board in  moving water. This size motor is the most popular among S4 and W700 users, as it offers a good trade-off between power and weight for people who must lift the motor or carry it by hand over long distances.These motors are also less expensive than bigger ones.

6 HP outboards

Outboard motors in this class weigh around 60 lbs, which makes them portable only for very short distances, and not for everyone. A 6 HP motor can propel an S4 skiff with one person on board at speeds up 18 mph, and it can propel the boat at 14 mph with three passengers on board. 6 HP motors are the second most popular motors among S4 users.

8 HP outboards

Outboard motors in this class weigh around 80 lbs. At such weight, these motors can no longer be considered as portable, and the only reason to use them is the fact that they are offered with electric ignition, which eliminates the need to start them by pulling a cord. The S4 outfitted with an 8 HP motor performs well in choppy water, but it could feel over powered for an inexperienced driver, which should avoid using such motors with their S4. Heavy users may benefit from driving with a U-jointed tiller extension, in order to move some weight forward from the stern to the middle of the boat.

6.5 HP mud motors

Mud motors are bulkier and heavier than regular outboard motors. A 6.5 HP mud motor weighs around 80 lbs, and it’s not portable. The reasons you’d want to use such a motor instead of a regular outboard of similar power are if you need to go in very shallow water (skinny water) and mud, and if you fish or hunt in water with plenty of vegetation and underwater obstacles. The S4 performs very well with a such a mud motor. We do not recommend using less powerful mud motors because typically, these motors require more power than regular outboard motors do.

Electric outboard motors

Some electric trolling motors are described by their manufacturer as “outboard motors”, namely comparable in power to small outboard gas engines. If you consider such electric motors, we recommend remembering the laws of physics, and applying the formulae for Kilowatts to Horsepower conversion, which are:

  • 1 KW = 1.34 HP
  • 1 HP = 0.745 KW

 

 

 

 

 

 

Choosing an outboard motor for your Wavewalk® 700 skiff

This article is an attempt to answer some questions that Wavewalk skiff owners ask in the process of choosing an outboard motor for it –

Short shaft or long shaft?

We definitely recommend using outboards that feature a long (20″) propeller shaft, and for multiple reasons, which are discussed in this article entitled Outboard motor propeller shaft length for Wavewalk fishing kayaks and boats »
We recommend not to be tempted by the availability and lower price of 15″ short shaft outboard motors, because such motors don’t fit the W700, and using one would never produce optimal results, even for a highly skilled individual with a lot of experience in boat outfitting.

Here is a list of long (L) 20″ shaft outboard motors currently available in the 2 to 6 horsepower range, and their HP rating:

  • Honda 2.3 HP (air cooled), 5 HP
  • Suzuki 6 HP
  • Evinrude 6 HP
  • Tohatsu 3.5 HP, 4 HP, 5 HP, 6 HP
  • Yamaha 2.5 HP, 4 HP, 6 HP
  • Mercury 3.5 HP, 4 HP, 5 HP, 6 HP
  • Mariner 3.5 HP, 4 HP, 5 HP, 6 HP

Recommended reading –

Air cooled or water cooled?

Water cooled motors are quieter but heavier than comparable air cooled motors.
The only motor featuring on the above list that’s not water cooled is the Honda 2.3 HP. It is very lightweight, and works very well, but being air cooled makes it considerably noisier.

Note: Outboard motor manufacturers recommend flushing the motor’s cooling system with fresh water after every trip in saltwater. It’s possible to flush an outboard with a garden hose outfitted with a special adapter.

4-Cycle or 2-Cycle engine?

Nearly all new small motors on the market are 4-Cycle (4-stroke) and not 2-Cycle (2-stroke).
The advantage of the 4-Cycle system is twofold –

  1. The motor runs on regular fuel, and there is no need to mix it with oil.
  2. A 4-Cycle motor is cleaner, namely it emits far less stinky fumes than 2-cycle motors do.

Some experts argue that for the same displacement of its combustion chamber (cc, volume, size), a 2-Cycle engine in more powerful than 4-Cycle one, but we think that convenience and fresh air are more important.

electric or gas?

Many Wavewalk owners outfit their W500 and W700 with electric motors in the 30 to 50 lbs thrust range, and some go as far as 70 lbs thrust. They use their electric kayaks and skiffs for assisted paddling, recreation, touring, trolling, fishing, snorkeling, etc., but we prefer not to include electric motors in our list of “real” outboard motors for two reasons, which are:

  1. Power – Although some small electric motors are offered as “outboard motors”, just looking at their basic, objective power rating makes us think that they are too weak. Kilowatts to Horsepower conversion: 1 KW = 1.34 HP, and 1 HP = 0.745 KW. Consequently, an electric motor can work well on flat water and at a moderate speed, but not necessarily in adverse conditions, namely strong current, strong wind, etc.
  2. Range of travel – A gallon (3.8 liter) of fuel costs a few dollars, and it’s enough for a typical small outboard motor to run for 4 hours at a high RPM, or an entire day at a lower RPM. You can refuel a small outboard’s built-in fuel tank when you’re on board your Wavewalk®. You can take several gallons of fuel with you on a long camping trip, and you can buy more fuel almost everywhere, while recharging an electric motor’s battery can take half a day. Therefore, gas outboard motors offer a reliable and convenient solution whose price / performance ratio is unbeatable by any electric motor available today.

Weight

All small outboard motors listed above are considered to be Portable. However, between the 29 lbs of the 2.3 HP Honda and the 59 lbs of the 6 HP motors there is a considerable difference, if you need to carry the motor by hand over a distance.

The shallow water position

Most of the small outboard motors listed here offer to lock their propeller shaft in an intermediary position between the vertical (down) and horizontal (up) positions. In this intermediary, slanted position, the propeller drafts less than in the vertical position, and this allows for driving the boat at a moderate speed in very shallow (‘skinny’) water. Therefore, if you’re looking to fish in skinny water, we recommend that you look for this feature.

gear shift lever

Most outboard motors on our list feature a gear shift level, and this is a good thing, because the alternative is a centrifugal clutch that lacks an absolute neutral position. The absence of a full neutral gear can make starting the motor a little tricky, if you’re a beginner.
Our preference goes to the outboard motors that feature the gear shift lever at the front, rather than on their side. The frontal position makes it easier for the driver to access the lever whether the motors points left or right, and even if the driver is facing forward.

built-in fuel tank

All the above listed outboard motors come with a built-in (integrated) fuel tank, and this is a convenient feature considering the alternative is to have a fuel line run from a separate tank to the engine. When you operate such a small craft as a Wavewalk, simplicity becomes increasingly important.

propeller

The propellers that come standard with these outboard motors fit Wavewalk’s kayaks and portable skiffs. Typically, these motors propel much heavier boats, which is why the propeller’s diameter and pitch which determine output in terms of speed and torque are of no real consequence to the owner of a Wavewalk under normal conditions.

price and brand

All the brands listed above are known to produce quality motors, and in fact some of them produce motors for others. For example, Mercury is a Tohatsu brand. This is to say that we see no reason to pay more for a particular name brand, and we recommend to consider only the motor’s technical attributes, and its price.

HP rating – can i overpower my skiff?

6 HP is the absolute maximum for which the W700 is rated, and this is only for its RIB model. Overpowering your Wavewalk can be hazardous, and if you use the wrong motor mount you’d be calling for trouble. This said, if you happen to own a 20″ shaft 5 HP motor and your W700 is rated for a 4.5 HP motor, you can keep your motor, and you won’t necessarily have to get a new one. Similarly, if your W700 is rated for up to 4.5 HP and you found a nice 4 HP that you like, you’d be fine with it.

motor mount

If you choose to make a DIY mount for an electric trolling motor, chances are that you’ll succeed, since these motors are so weak that they’re not likely to cause trouble. But this is not the case with the gas outboard motors in the range that features on the above list.
There are several issues to overcome with motor mounts, and the motor’s weight is the least of them. The main problem is that operating at the end of a 20″ lever, the motor’s propeller generates a great amount of torque, especially at high speed, in rough water and when making sharp turns at high speed. This torque can twist and crack a 4×2 timber, and pull out nails and screws from their place. After having seen motor mounts get broken by outboard motors ranging from 6 to 3.5 HP that were mounted on them, we strongly recommend not to build a DIY motor mount for these motors, and to use only the motor mounts that Wavewalk recommends.

alternator

Some of the more powerful outboard motors listed here can be outfitted with an alternator and an AC to DC converter. Note that such accessories cost hundreds of dollars.
The electric current produced by this system can be used to power lights on board, or to charge a trolling motor’s battery. Such setups are common in bigger boats (e.g. bass boats) that feature much more powerful motors. Although some Wavewalk owners have outfitted their W700 with two motors (a powerful one for driving and a small one for trolling), we don’t know of anyone who’s outfitted their outboard motor with an electric current generation system.

Why an outboard motor?

Skiffs, Jon boats and other small boats sometime come with other motors, among which are air drives or air motors (large diameter propellers) for running marshes and flats, jet drives (similar to personal watercraft, a.k.a. jet-ski), long shaft mud motors for going in shallow water and over obstacles, and outboard motors that run on propane.

While each of these motors offers certain special advantages, and we’d love to see the W700 outfitted with any of them, as well as with other propulsion systems ranging from sails to oars, and even pedal drives… we think the common small outboards such as we listed here offer the optimal mix of price, performance, reliability, versatility, ease of use, and ease of maintenance – Just think how common are boat dealerships and repair shops that service these motors… And if you know how to use your outboard motor and you take care of it, it’s truly a wonderful thing that you’d enjoy for years, and possibly even decades.

Outboard motor propeller shaft length for Wavewalk fishing kayaks and boats

November 12, 2016

Wavewalk will no longer support the installation of any outboard motor whose propeller shaft is shorter than the standard 20″ long (L) on its W500 fishing kayaks and W700 portable boats.

How to measure an outboard motor shaft’s length?

An outboard motor’s propeller’s shaft length is measured from the top inner side of the motor’s clamp bracket to the horizontal anti-ventilation plate located above its propeller. Read more about how to measure this length precisely »

The outboard motor industry has determined four standard lengths for outboard motor shafts, which are:

  1. 15″ (S) “Short”
  2. 20″ (L) “Long”
  3. 25″ (XL) Extra Long
  4. 30″ (XXL) Extra Extra Long

For both the Wavewalk 500, 700 and 4 series, the length we recommend is 20″ (L).

What’s wrong with short shaft outboard motors?

Depending on the type and quality of the motor mount’s installation, the use of shorter shaft motor (electric or gas) can result in any of the following problems:

  1. Motor mount’s mounting plate too high – Strong vibrations and loss of power due to ventilation that occurs when the propeller rotates at high speed too close to the surface, and its top part goes through a mixture of water and air bubbles coming from the surface.
  2. Motor mount’s mounting plate is too low – The motor mount’s mounting plate’s lower side scoops water and generates excessive spray, some of which can find its way to the back of the cockpit, and some to the top part of the motor.
  3. Motor mount too far behind the cockpit – Access to the motor’s controls is not easy, including for starting it, shifting gears, using the choke button, and refilling gas. Driving is harder too. The driver is forced to drive from the cockpits rear end, instead of driving from the middle of the cockpit.
  4. Motor mount’s mounting plate too low, and mounting plate too close to the cockpit – The motor’s top part is prevented from tilting downward in case the lower part of the propeller hits bottom or a submerged object and gets pushed upward automatically, in order to avoid damage. If this basic safety function is disabled, the propeller is exposed to severe damage, and so is the propeller shaft.

For the above stated reasons, Wavewalk does not recommend using any motor, electric or gas powered, whose propeller shaft is shorter than the 20″ (L) standard length.

Why does Wavewalk restrict its support now?

In the past, Wavewalk supported owners’ efforts to outfit their W500 kayaks with short-shaft motors. This policy stemmed from the fact that long-shaft motors in the 2-3 HP range are harder to find than short shaft ones, and we don’t recommend more powerful motors for the W500 series.
Installations of short shaft motors on Wavewalk kayaks and boats worked, but they were sub-optimal, since there is practically no way for a 15″ setup to match the performance and convenience that a 20″ outboard offers when properly mounted on a Wavewalk.

Last year we came out with the W700 series that’s compatible with several 20″ (L) outboard motors up to 6 HP, which is to say that since then, Wavewalk owners benefit from a much wider choice of outboard motor models.

Currently, the only outboard motor under 3 HP that we recommend is the lightweight, air-cooled 2.3 HP 20″ (L) 4-Cycle Honda.
Several outboard brands offer water-cooled, long shaft (L) motors in the 3.5-6 HP range, and our preference goes to Tohatsu, since these outboards (also sold under the Mercury brand) feature a gear shift lever in the front side of the motor, where it faces the user, which makes them easier to use.
Other 20″ (L) quality portable motors in the 3.5-6 HP range are offered by Yamaha, Honda, Suzuki, Evinrude (6HP only), etc.

Keeping the cockpit of your Wavewalk dry at sea

When you paddle your Wavewalk in waves without covering the front end of its cockpit, some spray may get inside, especially if you paddle through big surf. The water is drained to the bottom of the hulls, and it flows backwards to the rear part of the hull tips. Altogether, this is rather insignificant.

When you drive a motorized Wavewalk in the ocean for a long time, at high speed and through waves, your boat generates more spray, and breaking waves can result in more water getting into the cockpit. A Spray Shield works to minimize intake from the front, but not from the sides. Some water may accumulate on the bottom of the hulls, at the rear end of the boat. A few gallons of water would be unnoticed, but having effective means to remove any amount of water at any time is highly recommended, simply because stuff happens, and you’d better be well prepared for any case.

Comparing different solutions

1. One-way valves

Many motorboats and sailing boats feature one-way valves at the rear end of their hulls. When the boat moves in the water at high speed, the low pressure behind its stern causes the valve to open, and pulls out the water that accumulated at the bottom of the hull, namely the bilge.
A hull outfitted with such a valve is called ‘self bailing’.
Needless to say that SOT kayaks described by their manufacturers as “self bailing” are not, and the misuse of this term is misleading.

After much consideration, we decided not to outfit the hulls of the Wavewalk with such valves, for two reasons, which are:

  • Unlike big motorboats, a Wavewalk can be dragged on the ground and over rocks, and this might damage the valves.
  • One-way valves can get jammed, and since the Wavewalk often goes in shallow water that’s mixed with sand and mud, and where vegetation can be abundant, the possibility of such malfunction cannot be disregarded.

2. Electric bilge pump

Battery recharged on board –
Some small outboard gas motors (e.g. Tohatsu, starting at 4 HP) offer the option to add an alternator (electric current generator) and an AC to DC converter. Thus, the motor continuously produces an electric current that can charge a battery that would power an electric bilge pump and/or an electric trolling motor.
This solution sounds perfect – just press or turn an electric switch, and bail the water out. And if you get an automatic pump, you don’t even have to remember to activate it.
But a closer look at the details of this solution revels some problems:

  • Cost – The combined cost of an alternator and converter is around $450. The cost of a battery and an electric bilge pump would bring the total cost of this solution to over $500. It may not be a prohibitive price, but it’s still a considerable sum in the context of a Wavewalk boat.
  • Vulnerability – Keeping a battery and electric pump somewhere in your Wavewalk may not be enough, and you’d need to secure both, so that in case of an accident they would remain inside the cockpit and be fully operational when needed the most. This could prove to be somehow hard to achieve.

Battery not rechargeable on board-
An electric bilge pump powered by a battery that isn’t being continuously charged makes sense, because unlike propelling the boat, pumping a few gallons of water out of its hulls require little power.
The downside of this simple solution is having to remember to charge the battery before each motorized trip offshore, and the possibility that in case of an accident the system could stop working.

3. Hand bucket

Simply a square bucket with a handle (or without one) that fits into a Wavewalk hull, and used as a bilge bucket.
It works, but only in case there is a lot of water in the hull, namely that the water is deep enough, and the user faces the water. But such a scenario is extremely unlikely, and in a typical case only a small quantity of water may accumulate at the bottom of the rear end of the hulls, that is far behind the driver.
This said, it wouldn’t hurt to have a bucket on board, as an addition to the solution that we recommend, which is:

4. Hand pump

A 36″ long, lightweight hand pump costs $29 at Lowe’s.
It allows to pump water from the rear end of the hulls while the user sits facing forward. This is a major advantage, ergonomically speaking, and in simple terms of convenience.
The pump provides a sturdy, simple, and easy to operate solution that you can count on. The piston is lubricated by the water itself, and this makes pumping easy. Capacity wise, four strokes bail out one gallon, and since it’s hard to imagine having to bail out more than a few gallons at a time, the effort required is almost negligible.
The pump features a simple filter at its end, and this prevents it from getting jammed.
If there is a perfect solution, we think this is it.

Manual bilge pump for fishing kayak 36 inch

Manual bilge pump, 36″ long

One step at a time

By Dario Lazaric

Melbourne, Australia

I haven’t been in a lot of kayaks before.
I’ve been out with my wavewalk a couple of times, even caught a fish. Stood up, paddled, good fun.
It was tough paddling against the wind and waves, but I’m very happy with it, and it can do much more than in the conditions I took it out in.
Will take it out again sometime when the wind isn’t too strong. I want to get the motor on board as well, but one step at a time. I need to get an anchor, how do I attach it?
Very happy with it. I feel very safe and happy in the wavewalk.

 

walking-the-kayak-to-the-water

 

first-time-out-in-the-W700

 

mercury-4hp-outboard-motor

4 hp mercury outboard. Fitting the transom mount

 

outboard-propeller-draft

20″ propeller shaft

 

wheels-for-motorized-kayak

Will need wheels to carry the wavewalk to the beach with the motor attached to it.


More from Dario »