Outboard tender, comparing the best models from 2.3 to 3.5 horsepower

What is the right outboard motor for your boat tender? The comparative article sent to us by reader Giacomo Marco Toigo we are sure will help you in your choice!


A few days ago I came across a post online requesting information about an outboard engine from Honda, the now famous little air-cooled 4-stroke BF 2.3, sympathetically referred to by some as “the Lawnmower” because of the derivation believed to be agricultural and because of the noise–definitely typical!

Among the responses I found many “absolutes,” and so, intrigued, I took it upon myself to inquire further and summarize what the market offers among the most commonly used engines of up to 2.5 horsepower.

A premise: technical data aside, these are just my own reasoning and considerations drawn from documentation and feedback that can be found and not interested. I also want to be honest and will not hide which outboard I purchased and for what reasons. This comparative is not meant to be an advertisement or an intent in highlighting or shading any engine, it is just my effort to lend a hand to everyone in having a bigger picture, nothing else. Take it like this, light as the wind and unpretentious.

In order of increasing displacement, six engines are considered: Honda BF 2.3, Suzuki DF 2.5, Yamaha F2.5B, Mercury F2.5 MH, Tohatsu MFS 2.5, Selva Guppy 2.5 hp.

I also had to mention the Mercury F3.5 MH and the Tohatsu MFS 3.5, both 3.5 horsepower, for reasons that will become clear to you as you read the article.

The Suzuki DF 2.5 falls within the lightweight three (Suzuki, Honda, and Selva) at 13.5 kilograms and, compared to its predecessor, has been redesigned by refining it. In the past, the carburetor had to be disassembled and cleaned quite frequently to solve a problem of inconsistent idling with a few too many shutdowns. The cooling water drain then tended to clog easily being rather small. After some investigation on various holy YouTube and holy Forums, mostly foreign, I have verified that these difficulties have indeed been solved with the new engine that seems to have something extra in terms of thrust as well.

Not that the old ones were unappreciated: in more than one video I found detailed guides for fixing any problems that might have occurred. In one video in particular, where they had disassembled it completely and reassembled it, they even labeled it as “like the good old Russian things” complete with two good vigorous pats on the shell to confirm its sturdiness but more importantly its repairability, although the Japanese in Suzuki might not like the comparison. Perhaps it was precisely all this established documentation and appreciation that convinced me to go for this model and could therefore be determining elements in the choice for those who, like me, appreciate and are able to personally get their hands on it if it should one day be necessary.

The propeller is aluminum, as with the Selva and Yamaha, a good thing. The noise level is low (67 db)

If you are inexperienced and have the old model, it should be considered that you will have to entrust it to an honest mechanic, and for the new one you will instead have to rely on the warranty, which is 3 years.

For all those less skilled and not very fond of getting their hands dirty, in the long run the Honda or Selva, both with 5-year warranties, might be a better choice if you still want to stay light. Alternatively, one could evaluate the Tohatsu to take advantage of the 7-year warranty, which is really a lot.

The Honda BF 2.3 is very popular and is the only one with air cooling.

Thus, one does not run into the possible problems of the impeller and exhaust, as well as boasting some familiar ease of start-up.

However, there is also significantly more noise (82 db) and less power, with the displacement being the lowest in the entire category.

The feature of the centrifugal clutch should also be kept in mind since, if stationary for some time, it can give some trouble but especially does not allow you to accelerate in neutral.

The propeller is made of plastic.

On its side, the Honda has a 5-year warranty, the consistently low weight of 13.5 kilograms, and the simplicity of operation that make it incur little need for extraordinary maintenance and have in fact decreed its success by being the first to choose these combined routes.

In response to many, regarding whether or not it was possible to run it “dry,” I quote the excerpt from the manual to be referred to moreover in terms of warranty: “if the engine is to be running, make sure that the water is at least 150 mm above the anticavitation fin, to avoid overheating of the engine.” If the designers wrote this there is actually a reason. Then again, it is enough to think that cooling in the foot is relied on oil. Not infrequently, unloading this oil at the end-of-season change, several reported that “the smell was burnt oil.” One reason is probably just too frequent dry start-up with some acceleration for excessive times and the resulting dissipation that falls entirely on the oil in case the stem is not submerged in water.

Looking at the exploded views of the engine, I think it is a bit more labor-intensive in terms of disassembly and extraordinary maintenance; not that it is more complex, if anything the opposite, just more labor-intensive because of the way it is structured. It has been reported that some galvanized screws are particularly prone to corrosion, so keep an eye on them given what has already been said. Even the carburetor is not exempt from cleaning, as with all the others for that matter: let us remember these things when we hear that it is “eternal” or “unstoppable.”

In summary, a particularly robust engine if its limits are respected, requiring less maintenance but needing, in case of problems, some disassembly. In some cases, out of warranty, it might almost be worth going to new if you consider the labor. It is not for my philosophy but, for those who prefer to “use and forget” albeit to a certain extent, it is perhaps the most suitable of all. However, do not use it to mow the lawn.

Selva Guppy 2.5; I made this comparison starting with the smaller displacement of the Honda BF 2.3 (57 cc) and gradually went up. As I expected, the increase in displacement resulted in an increase in weights to the Mercury’s 18 kg and the Tohatsu’s 18.4 kg. But then I came across a nice surprise: the Selva Guppy 2.5 with a displacement of 87 cc, which is the largest displacement in the whole category, is the only one to keep its weight at 13.5 kg. I would say a nice surprise since, to get the same horsepower, the RPM will still be lower, with less noise and wear plus several other known advantages easily imaginable. Looking at the engine exploded views heightens interest. If I had studied it better earlier, I would have considered it more: in this regard I might say that Selva unfortunately does not shine in marketing. It hasn’t been on the market long, and that honestly had held me back a bit. Given the price found in promo at 700€, the 87 cc displacement, the low weight of 13.5 KG and the 5-year warranty, I think it may prove to be perhaps the most inviting of all.

The other engines, falling in a higher weight class, deserve a somewhat different discussion. In fact, we go from about 13 kilograms for Suzuki/Honda/Selva to about 18 kilograms for Yamaha/Mercury/Tohatsu. Excluding Yamaha, it is fair to keep in mind then that they have the same weight as their 3.5 hp counterparts, such as the Tohatsu MFS 3.5 hp or Mercury F3.5 MH.

The Tohatsu MFS 2.5, without considering the weight of 18.4 kilograms that counts it as the heaviest, is certainly attractive because of its 7-year warranty. He is the only one in the entire category to offer so much. I think it would be difficult for the house to propose them if they didn’t think it was reliable. However, it overlaps with the 3.5-horsepower Tohatsu MFS 3.5, which still boasts the same weight and warranty.

The actual price found varies very little, and I honestly do not understand this overlap except perhaps because of structural limitations of the tender, when very small, or of fuel consumption, which in any case remains very low. The propeller is made of plastic.

For the Mercury F2.5 MH the same reasoning applies as for the Tohatsu; at 18 kg it is only slightly lighter than him and remains one of the heaviest for the 2.5-horsepower category. It is a time-tested and documented engine but it too finds overlap in the 3.5 hp Mercury F3.5 MH, albeit with a more significant discrepancy in terms of cost gap than the 2.5 to 3.5 hp Tohatsu’s transition and without such a long warranty. The propeller here is also made of plastic material.

The Yamaha F2.5B has a weight of 17 kg and, unlike Mercury and Tohatsu, does not find overlap with a 3.5 hp Yamaha model. In terms of design, quality is high and so is reliability. Needless to say, the propeller is made of aluminum. It was difficult to find people complaining about it online. Spare parts perhaps cost a little more, both for routine use and maintenance and for extraordinary maintenance but more unlikely to be needed over time. Honestly though, I didn’t find it very interesting. The list price is in line but the real lack of discounting or promotions makes it unattractive to me, counting the cost as the highest in the category and the weight always important at 17 kg. I think that by doing really heavy and constant use of the engine in areas where warranty matters relatively, it would certainly find its own logical sense in having it preferred over others.


The supply of small tender engines is expanding, with some manufacturers striving to fit within a weight on the 14 kg per 2.5 horsepower range. These are the most chosen ones actually because of a matter of bulk, weight and fuel consumption. For those who don’t get their hands on it, the Honda BF 2.3 leads the way, at least ideally and until you have barely more serious problems out of warranty.

For all those who apply “do-it-yourself” or have some familiarity, the new Suzuki DF 2.5 is an excellent choice because of the very extensive documentation. Definitely interesting is the Selva Guppy 2.5, which on closer inspection on paper of these three would be the one to consider most for features, pair and price.

There is no shortage of what I believe to be inconsistencies and overlaps for some engines: for example, I get the idea that the Mercury F2.5 MH and Tohatsu MFS 2.5 are born as 3.5 hp but are found with “throttled” carburetors, thus coming within the 2.5 hp threshold to cover the market range. Costs aside, since they are also identical in weight still at 18 kg, the 3.5 hp versions of these two engines are the preferred choice, with Tohatsu over Mercury offering a longer warranty of as much as 7 years.

The Yamaha paradoxically is the one that has least attracted me of this entire category, complicit perhaps in a high price. On quality there is no question and it is true that it is reliable and well designed but with a weight of 17 kg at this point it seems more logical to go for the Tohatsu MFS 3.5 hp: with 7 years warranty it denotes reasonable reliability as well as more power. What’s more, it costs significantly less.

My view is that the market is moving more and more decisively toward lightweight engines under 14 kg. For heavier weights, around 18 kg, it is not worth staying with 2.5 hp but rather moving toward 3.5 hp if the Tender allows it.

Doing this simple comparison therefore helped me and I found more than a few surprises, from the Selva Guppy 2.5 so little known but so worthy, to the curious overlap of some 2.5 horsepower engines with their own 3.5 horsepower models (Mercury and Tohatsu). I hope it can help you, too.

What is the best engine? Well, the truth is that there is no best engine but the engine best suited to one’s needs, just as with boats, to each his own!

Ultimately, perhaps we should also apply to engines what J.Conrad said about men and boats.

Dealing with men is as fine an art as dealing with ships. Both, men and ships, live in an unstable element; they go subject to arcane and powerful influences, and need their merits understood rather than their faults uncovered

The Mirror of the Sea, Joseph Conrad

James Mark Toigo


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