Tag Archive: outboard motor

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

Updated December 20th, 2017

The purpose of this article to answer a frequently asked question (FAQ) from prospecting clients, which is “What outboard motor should I choose for my S4 skiff?”

The answer is that the outboard motor and propeller you should choose for your S4 depend mainly on two factors, which are –

Power

  1. How much power you need: How fast you want to go, in what kind of water, and how many passengers you’ll have on board
  2. How important to you is the motor’s weight.

There is a trade-off between power and weight, namely that the more powerful the motor, the heavier it is, and the harder it is to carry it.

In any case, the motor should be a 20″ log shaft (L) model, and not a 15″ short shaft (S).

Recommended reading: How to measure an outboard motor’s propeller shaft length? »

Propeller Pitch

Another important trade-off that you should be aware of is related to propellers: High pitch propellers are designed to deliver more speed and less torque (thrust, push force), and they work best with lightweight boats such as the S4, while low pitch propellers are designed to move bigger and heavier boats at lower speeds, but they should not be used with lightweight boats such as the S4, since they might make the motor run at a too-high RPM.

Outboard motors manufacturers’ websites say that (quote) “UNDER NO CIRCUMSTANCES SHOULD YOU EVER USE A PROP WHICH WILL ALLOW YOUR OUTBOARD TO OPERATE ABOVE THE OUTBOARD’S RECOMMENDED MAXIMUM RPMs“. This means that you should avoid using propellers designed for use with very heavy boats, namely propellers in the low-pitch range.

Note that 20″ long (L) propeller shaft motors typically ship with propellers that are not necessarily optimal for very lightweight boats such as the S4. For example, the 6 HP 20” long (L) outboard from Tohatsu often comes with a medium range 8 pitch propeller, which is fine, but mounted on the S4, such a motor could drive the S4 12% faster if outfitted with a 9 pitch propeller.

Propeller pitch information is available on outboard manufacturers’ websites.

Since the S4 is a very lightweight boat, you should preferably outfit the outboard motor for it with the highest pitch propeller available for it.

Diameter – Don’t try to use a propeller from a small outboard with a bigger outboard, or vice versa.

 

SMALL OUTBOARDS

 

For the S4, small size means a highly portable but under-powered outboard motor.

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 power 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 these small motors noisier than bigger, water cooled motors.

Propeller pitch –
The Honda 2.3 HP comes with a 4.75 pitch propeller

 

MEDIUM SIZE OUTBOARDS

 

For the S4, a medium size outboard motor means powerful enough but still portable. Motors in this 3.5 HP to 6 HP range are the ones we recommend for most users.

3.5 HP outboards

Outboard motors in this range 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 to 11 mph, even in choppy water, and it can propel the boat at 8 mph with three passengers on board in moving water. This size motor is 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.

Propeller pitch –
For their 3.5 HP motor, Tohatsu recommends either the 7 pitch (Plastic) or 6 pitch (aluminum) propellers, for lightweight boats such as the S4 (under 500 lbs). We say get the 7 pitch propeller, unless you think that you need the more durable aluminum propeller.

 

6 HP outboards

Outboard motors in this range weigh around 60 lbs, which makes them portable only over short distances, and not for everyone.
A 6 HP motor can propel an S4 skiff with one person on board at 17 mph, and it can propel the boat at 12 mph with three passengers on board.
6 HP is the second most popular motor size among S4 users.

Propeller pitch
For their 6 HP outboard used with lightweight boats up to 500 lbs (such as the S4), Tohatsu recommends their 9 pitch propeller. The 8 pitch propeller would work too, especially if you intend to have the boat fully loaded, so that it would weigh over 500 lbs in total.

 

BIG OUTBOARDS

 

8 HP to 10 HP outboard motors are too heavy to be carried by hand, and they may be too powerful for inexperienced drivers to use safely. However, some of them come with electric start instead on manual start, which is a nice feature. They also come with an alternator that can serve to power small electric devices on board.

8 HP outboards

Outboard motors in this class weigh between 65 and 80 lbs. At such weight, these motors can no longer be considered as portable, and the main reason to use them is the fact that are offered with electric ignition, which eliminates the need to start them by pulling a cord. People who like driving at high speed may prefer these motors to less powerful ones. 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 towards the middle of the boat.

Note that these bigger motors don’t come with an integrated fuel tank, but this isn’t necessarily a problem, since external fuel tanks can fit inside the S4’s hulls.

9.8 HP and 9.9 HP outboards

We tested the S4 with a 9.8 HP Tohatsu and a 9.9 HP Yamaha outboard, and it worked well. Practically, this class of heavier and more powerful motors offers no advantage over smaller motors unless you’re a speed fan, and you’re also capable of driving small boats safely at such speeds. To those who want to take the risk of overpowering their S4 with such big motors, we recommend reinforcing the mounting plate.

We recommend that inexperienced drivers avoid using high power motors with their S4. Instead, they should pick a motor within the 3.5 HP to 6 HP range.

 

OUTBOARD MOTOR BRANDS

 

After years of testing motors and getting input from our clients, we can recommend all Japanese brands, namely Honda, Suzuky, Tohatsu and Yamaha. Mercury is a Tohatsu brand, and the small, portable motors offered by Evinrude are made by Tohatsu. Motors from all these brands are good, and your decision about which motor to use with your S4 should be based on factors such as price, weight, features, availability, warranty, etc.

 

KICKER MOTORS

 

A kicker motor is a name given to any outboard gas motor used on a big boat for trolling, or as a spare motor, and for positioning and driving sailboats over short distances when sailing them is not possible. Being used on bigger boats, kickers often feature a 20″ long (L) shaft, which is the right size for the S4, but the propellers used with them are typically low-pitch models that are not optimal for lightweight boats such as the S4.
If you buy a kicker, check its propeller, and if it’s not a model with the highest pitch that the manufacturer recommends for lightweight boats, replace it with such a propeller.

 

MUD MOTORS

 

Mud motors feature a surface drive, and they offer a huge advantage to people who want to drive in very shallow water, mud, water with many underwater obstacles, and water with plenty of vegetation.

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 OUTBOARDS

Electric outboard motors

Typically, electric trolling motors are not powerful, and they are designed to propel heavier boats than the S4 (e.g. bass boat, skiff, Jon boat) at a very low speed, namely trolling speed. This type of application requires high thrust (small pitch) propellers, and it’s also the reason why trolling motors are rated in thrust units (lbs) and not in horsepower (HP or KW) – When you buy such a motor, your primary interest is how big (heavy) a boat it can move, and not at what speed.

Some electric trolling motors are described by their manufacturers as “outboard motors”, namely comparable in performance to small outboard gas engines. If you’re interested in such electric motors, we recommend comparing apples to apples namely power units to power units, and not power to thrust, which is meaningless. Remember the laws of physics, and apply the formulae for Kilowatts to Horsepower conversion, which are:

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

No amount of words can overcome this reality.

Electric motors are discussed in the Electric Trolling Motor or Outboard Gas Engine section of this article »

 

Wavewalk S4 with a 6.5 HP mud motor – first test

By Chris Henderson

Fishing Kayaks of Gig Harbor

Today I was able to do my first test drive of the Wavewalk S4 with a mud motor!

As a duck hunter the potential for the S4 is incredible. Couple that with a mud motor and you can access places that others cannot go. I hunt tidal mud flats where traditional boat motors are difficult to use due to the changing tides (water depth) as well as the sand bars that constantly shift. The mud motor allows operation in very shallow water and lets me get over those sand bars. Other duck hunters hunt in flooded timber where the logs eat propellers for lunch and occasionally eat whole lower units. The mud motor is the only way to travel safely in those kind of swamps. That is why putting a mud motor on the S4 is like combining peanut butter and chocolate.
This was my very first run, so I have a lot to learn about operating this kind of motor.

There are a lot of different styles of mud motors out there and the cost can be very prohibitive. But I found a kit which is created by Mud-skipper called the Twister. Rather than a straight shaft it has a curved shaft. At first I was concerned that due to this the turning radius of the boat would be dramatically effected. As it turns out that fear was unwarranted. The two hulls actually keep you from turning too sharp which could cause you to overturn considering the nature of how the motor turns. The 6.5 hp was plenty of horse power and I cavitated way before I ran out of power.

Lots of experimenting to do to get it all dialed in but it was a great first test run.

 

 

 

 

 

 

 

 


 

More kayak rigging, fishing and bow duck hunting with Chris »

Trolling for Barracuda in the S4

By Captain Larry Jarboe

Florida Fishing Kayaks

One of my least favorite fishing techniques is trolling.

Putting a rod and reel in a rod holder and waiting for what seems like hours for a bite can be borderline boring. Then, dragging a fish against the movement of a slow moving boat as we do fishing for stripers or bluefish in the Chesapeake Bay diminishes the tug and pull of the fish. Imagine cranking in a 5 gallon bucket of water. Welcome to the successful outcome of a trolling expedition.

However, trolling from a Wavewalk S4 is a completely different experience. After good success with my kayak spinning rigs trolling custom fabricated lures in mangrove creeks and channels, I set off to find the perfect rig for trolling in the clear inshore waters of South Florida.

I finally settled on a Shimano TR200-G graphite reel loaded with 20 lb. test mono line on a 4′ kayak Ricky Rod made in Miami.

With this rig in hand and the outboard tiller in the other, a kayak trolling fisherman (or woman) can smoothly ease out line and control the action of the lure or rigged bait while steering the S4. Unlike leaving the rig in the holder, with the rod in hand, bites are easily felt and the hook set. Now, we are fishing and catching and really enjoying the battle.

In less than an hour, I caught 4 barracuda no more than a 1/2 mile from my house using this technique. All were released. But, I had to gently tow the last one back to the dock to safely release from the dive platform of my big boat. It was just too big and toothy to bring aboard.

My next project is to build a long distance de-hooker.

 

 

 

 

 


 

Larry offers guided fishing and diving trips in the Key Largo and the areas that surround it »

More fishing adventures with Capn’ Larry »

Maiden voyage with my Wavewalk S4 and an 8 HP Mercury outboard motor

By Paul Partridge

Rhode Island

It has a 3.5 gallon tank that fits perfectly in the 9 inches wide gunnel, and a hand bilge pump.
The maiden voyage was extremely lot of fun. Took it out by myself.
The outboard had a 9 inch prop, and it went way too fast. I’m going to calm it down. I’ll put a smaller diameter propeller on it, so it doesn’t go as fast. I think it was going between 5 and 6 miles an hour at idle.
It was pretty choppy but the boat handled it really well. A little scary at first, then I fine tuned it and brought the trim down.
I just ordered a handle extension.

 

Wavewalk S4 with DIY mounting plate and an 8 HP Mercury outboard motor

 

8 HP Mercury outboard with a 9″ propeller

Ladder for Wavewalk S4 diving boat

By Captain Larry Jarboe

Florida Fishing Kayaks

I can walk up this DIY ladder with no one in the boat. The motor counterbalances the load. It works so well it is even spoiling me for getting on board regularly.

Remove the stainless hinge bolt and the ladder easily comes off. But, I am keeping it on because it provides enough weight in the bow (10 lbs. maybe) to eliminate the need for a tiller extension when running solo.

 

Wavewalk S4 with ladder for divers

 

Full view of S4 diving boat

 

 

 


Larry offers guided fishing and diving trips in the Key Largo and the areas that surround it »

 

More fishing adventures with Capn’ Larry »