The Tohatsu 6 hp Outboard

The motor that came with my Excalibur sailboat was an old 8 hp long shaft Johnson SeaTwin.  It had given the previous owner troubles on almost every outing.  It got so bad that he began to carry an extra battery and a 50 lb. thrust trolling motor to get him back into the marina after fishing or sailing.  I knew that the Johnson engine, even if I had it a while to work on it, would never become the reliable engine I would need in order to motor from San Diego to Dana Point.  So, I decided to replace it.

The search for a light, quiet, smooth, economical new outboard began.  I had experience with Johnson and Evinrude outboards, and even though they are regarded as great motors, my experience with them has been negative.  I owned a 40 hp twin that I threw money at in an attempt to make it run reliably.   I worked on it for weeks and had it running great in the driveway, but out on the lake I would get far enough away from the dock to make paddling back inconvenient and it would invariably either die, or run on one cylinder, or not rev much past idle.  On the other hand, I had a Honda 50 hp triple on the same boat that was near new when I bought it, ran smooth and quiet and was plenty powerful for the aluminum runabout it propelled.  It never gave me problems, but I had to be very meticulous with fuel system maintenance.  If I didn’t drain the carburetors after each use, the gasoline would spoil, gel and clog up the idle jets, necessitating replacement because the orifices were so small that they couldn’t be cleaned out.

I needed to decide how powerful I wanted to go.  While I would have loved to have a 15 hp motor in place, that wasn’t practical.  I took rough measurements of the well opening and tried to determine if any 15 hp motors would fit.  The housing and foot of each motor seemed big enough to make fitment difficult, if not impossible.  In addition, I did not want to leave the motor in place in the well at all times, which meant I would have to pull the motor after each trip or outing.  Even if I could get one to fit, the 15 hp motors were just too heavy to manhandle from my truck to the boat every trip.

The next size down in terms of overall size and horsepower was the 10 hp or less twins.  Most of these are rated at 9.8 or 9.9 hp because some lakes don’t allow motors 10 hp or larger.  In other areas, there are additional taxes on 10 hp or larger motors, so even though they may seem less, all are about 10 hp.  All of these motors are two cylinders and all weigh about 95-100 pounds.  I would have liked to have had the opportunity to carry each one and move it around a little as well as see which model fit best in the well, but that wasn’t possible.  None of them are so heavy that I can’t manhandle it, but I’m 43 years old now, and my ability to lift and move a 100 pound motor isn’t likely to get better as I age.  Even though I really wanted a two cylinder, I felt that a 60 pound motor, even one with only about half the power, would be the better choice.

The first motor I was inclined to buy was the Honda.  The lightest motor they offered was only available as a 5 hp assembly.  The other manufacturers offered 6 hp motors, and even though 1 horsepower doesn’t seem like a big difference, 5 horsepower is only 83% of 6 horsepower, so the Honda was eliminated.  I considered Suzuki’s 6 hp outboard but could find very little real world review of its performance, and so eliminated it.  This left the Tohatsu, Nissan Marine and Mercury outboards.  All three of these are manufactured by Tohatsu.  The Nissan Marine motor is considered the premium brand version of the Tohatsu.  It is identical except for color and stickers and costs about 5 – 10% more.  The Mercury is manufactured by Tohatsu using the same mechanical parts but it has a different hood and a different tiller control.

I decided to purchase the Tohatsu branded outboard and while it has been a good choice for the boat, it was not the best choice for the move from San Diego to Dana Point.   My budget allowed me to purchase a brand new motor and I added the alternator kit to charge the battery set and the sail-pro elephant ear propeller to push the slow, heavy sailboat.  A single cylinder four stroke is best used for short periods of time to get the boat into and out of the slip and harbor. The Tohatsu 6 hp protested every minute at full throttle and left a ringing in my ears if I kept if there for a long period of time. On the other hand, I never felt severely under-powered with this motor and the sail-pro propeller. I would not have been able to lift the 9.8 hp out of the well several times in a day as easily as the smaller motor.  The size of the leg of the larger engine would definitely result in more drag when under canvas alone and with the engine in the well.

At 65% throttle the Tohatsu is relaxed and quiet and relatively smooth and gave me an honest 4 – 5 knots. I covered approximately 70 miles over the water in two days. I ran the engine a total of fourteen hours and burned exactly eight gallons of gas. An average of nine miles per gallon and five miles per hour over the course of the trip is respectable.  Later, it burned less than 1.5 gallons while motoring 20 miles up the coast in a dead calm.

When I got the engine home I checked the amount of oil in the engine while I changed it. I burned almost no oil and the color of the oil was still acceptably clean at the fourteen hour mark. The longer it ran, the smoother it ran.  The only time the prop even hinted at coming out of the water was when it was heeled way over and turning–a situation I probably won’t be in again.

I was not satisfied with the steering friction lock and experimented with several ways to lock the steering in the straight ahead position.  The friction lock works well for adding or subtracting effort in moving the tiller handle from side to side but is not intended to hold the motor in a single position.  A lock separate from the friction adjuster should be available on all smaller outboards, even if it is in the form of a bracket that can be purchased and added later.

My solution continues to evolve, but the first finished version worked well on the trip from Dana Point to Long Beach recently.  I decided to fabricate a bracket that wrapped the tilt tube and bolted to the upper engine bracket in two spots.  It worked and would have been very strong, but would have required removal of the tilt tube bolt in order install or remove.  I wanted something that I could easily disconnect with hand tools without separating the motor and drive assembly from the mounting plate.

The second version included about one half of the original design.  It required me to replace the single tilt tube bolt with two stainless steel bolts so that one side would continue to be bolted in place if the bracket was unbolted and completely removed.  I lined up a piece of square tubing with the tilt tube and angled it upward to meet with a second piece of square tubing that had the hole drilled for mounting to the engine.  After measuring both pieces several times, I welded the two pieces together so they met at the correct angle.  I then finished each edge by closing off and sealing the square tubing and used round tubing to close and seal the bolt holes.  After an hour or so of grinding and sanding, the fit and finish was correct and I sent it to the powder coaters to have a corrosion resistant gloss black finish.

I placed stainless fender washers and rubber insulators at each point of contact between the engine and bracket and bolted it in place.  I used nylock stainless nuts to allow for the insulators to be pre-loaded, but not fully compressed, and not loosen.  The insulators act as a cushion to absorb some of the natural rocking tendency of the power head.

After installation, I measured again and am confident that it is pointing straight ahead.  During the second extended motoring trip, from Dana Point to Long Beach, the engine lock worked perfectly and did not transmit excessive vibrations to the hull.

If only Tohatsu would have offered this in the first place.

I am working on a third version that will lock the engine in place but allow minute adjustments to the angle of the engine if they are necessary.

The Tohatsu 6 hp was a good choice and I am confident it will serve me well but I still would like to work a little more at fitting a 10 hp non-tiller motor with cockpit mounted permanent controls in the Excalibur.

I did read a report from a poster on a sailing forum that claimed to have tested the Tohatsu 6 hp motor and found it to be woefully underpowered.  I can say that my engine has adequate power for my sailboat.  It pushed me against the tide out of San Diego Harbor and through the rolling swells out of Oceanside Harbor.  I am sure, however, that it could be put into realistic circumstances where it would be lacking for power.  I would not push it into a heavy surge or up against breaking waves.

The Tohatsu motor has proven to be a reliable, very efficient, adequately powered motor for my Excalibur.  It is smooth at lower power settings.  On the other hand, like all single cylinder outboards, it does vibrate when pushed hard and is loud when mounted in the well.

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9 thoughts on “The Tohatsu 6 hp Outboard

  1. Todd,
    I use a Nissan 8hp, long shaft (20 inches), but a 10hp would be better. It is similar to your Tohatsu as they are related companies. The 8 is fine, but in rough weather the 8 still struggles. I think it is because the boat is so light. The boats originally came with small engines like 3 hp seagulls. The 8hp gives me more reserve power in storms or squalls. I have my outboard well sealed and a bracket on the transom. It is a little unsightly on the transom, but it gives you more maneuverability for tight corners at the dock even with the spade rudder. This boat would do well with a saildrive or electric motor that was regenative.
    Thanks Mike

  2. I have a 69 Excalibur and am looking for a new outboard for the well. Considering an extra long 25″ 6hp mounted in the well. Do you think that this would help with the cavitation issues that have arisen with my current 3.5hp 20″ shaft Merc?

  3. I have a Tohatsu 6hp sailpro from 2004. I bought the outboard in January 2012. I just learned of corrosion through the engine block – it is a pretty impressive hunk of aluminum that was corroded. I would be curious to know whether anyone else has had issues with this.

    • Yours is the first I’d heard about with corrosion problems. Is yours left in the water? Was it flushed after each use? Any engine can suffer from block corrosion but I think it’s a relatively rare occurrence and I know the Tohatsu/Nissan is rated for use on saltwater. Sorry for your troubles.

  4. Hi Todd. Good writeup on the Tohatsu 6 hp motor. What is the sailpro elephant ear prop? We’re you still able to fit the prop on the outboard through your lazarette hole? Is it much bigger than the standard prop? I now have an old Johnson 6 horse, currently being worked on. It barely fits and leaves only 1/2 inch clearance behind the motor. I’m trying to find out the dimention between the inside end of the back motor bracket and the back of the housing. Can you help?

    • Thanks, Paul. The elephant ear prop is not a lot larger in diameter and easily fits through the well opening. Most of the newer outboards have smaller legs than the older ones, so if your old Johnson fits, a new Nissan/Tohatsu should without a problem. The power head and cover are also much smaller than most of the older outboards. If your Johnson fits, even tightly, I’m pretty confident the Tohatsu will. I’ll try to get some hard measurements for you. What kind of boat is it going in and how does the outboard mount?

  5. Just purchased a Tohatsu 6hp sailpro and have completed a break-in period of 15hours. Engine works well except it is very hard to restart after running for a period of time, then shut off for 30-60 minutes. Specifically, i had run for 2hr, then shut off for 45min. Did this trip three times with the same result – very hard to restart; ie taking 8-9 hard full pulls with or without choke to get restarted. Anyone else experience this? If so, what was done to resolve it? At this point, my wife is unable to restart the engine after running…

    • Craig,

      Are you or your wife pumping up the fuel bulb? I’ve noticed that my engine is hard to start in the same situation as you describe unless I pump the bulb until its tight. If I do, it starts in a pull or two.

      Todd

  6. Hi Todd. I bought a Tohatsu 6 horse 25 inch shaft for my sailboat. It is in a lazarette on a 23 Sea Sprite. I expected the engine to be quiet compared to my old Johnson 2 stroke. It’s noisy as hell. Also, the cowling does not fit tight and vibrates to add to the noise. My wife’s been giving me strange looks as I assured her that it would be quiet. It’s also tricky to start sometimes. My wife has been giving me strange looks. Paul

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