# Outboard Fuel Economy/Sizing



## tschmidty (Sep 25, 2008)

I am looking for an outboard for my 23' 2800lb Spirit 23 and wanted to get some opinions on outboard economy and sizing.

Here are some options I am looking at.

1. 5hp Nissan NS5B 2 Stroke. 0.7 GPH per nissan at WOT, 41lbs

2. 9.8 Tohatsu 4 Stroke, 1 GPH WOT, 89lbs

3. 9.9 Johnson 2 Stroke, 1.3 GPH WOT, 72 lbs

I am leaning towards the Johnson since it has electric start and an alternator along with an extra long shaft, but the 5hp nissan seems to be a good motor from what I hear.

My understanding is that the 2 stroke will be less efficient at part throttle and with 9.9hp I would probably never run at full throttle. Is it enough of a difference that the 5hp would be a better choice for fuel economy reasons? Not to mention half the weight (my mount can handle the weight though). Or the 4 stroke since I am not a huge fan of 2 strokes and I like the idea of not mixing fuel not to mention environmental reasons.

Anyone have any recommendations or thoughts on what would be appropriate. I plan to do a few long trips where I would end up motoring a fair bit so fuel economy is a factor but not an overriding one.


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## Alex W (Nov 1, 2012)

If I were in your situation I'd buy a new Tohatsu Sailpro (6hp, extra long shaft, 4 stroke). They aren't that expensive, you'd have the peace of mind of a new motor, and they are light which makes servicing them that much easier. The fuel economy is good too and they include an alternator and electric start.

A 9.8 seems like overkill for a 2800lb 23' sailboat. 

2 stroke is easier to service but loud and lower fuel economy and the exhaust usually smells bad. If you just used the motor to get in and out of a slip that would be fine, but for long trips it'll be annoying.

The Tohatsu 9.8s that are meant for sailboats (25" shaft, 4 blade low pitch prop) include alternators and electric start as well.


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## tschmidty (Sep 25, 2008)

Well that would be ideal, but I am trying to avoid buying new since that is $1530 and the motors I am looking at are $400-$800. The bonus on the Tohatsu 9.8 is that it is a long shaft and I can add an alternator for relatively cheap. It is heavier than the 6hp (89 vs. 59) but it is a 2 cylinder which is supposed to be smoother. If I could find one used I'd be all over it.


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## dabnis (Jul 29, 2007)

tschmidty said:


> Well that would be ideal, but I am trying to avoid buying new since that is $1530 and the motors I am looking at are $400-$800. The bonus on the Tohatsu 9.8 is that it is a long shaft and I can add an alternator for relatively cheap. It is heavier than the 6hp (89 vs. 59) but it is a 2 cylinder which is supposed to be smoother. If I could find one used I'd be all over it.


Not familiar with your boat but unless it has a well a long shaft is far better than the standard 16" transom shaft. I had a Coronado 25 at about 4,500 lbs and started with a 6HP 2 stroke which was OK in calm water but somewhat challenged in the rough San Francisco Bay conditions. My guess is that 6HP would be adequate for your boat. I have had both similar size 2 and 4 Strokes and although the 2 stroke may burn a little extra fuel the incremental cost difference would probably be small. I bought a new 6HP 4 stroke Tohatsu about a year ago and it runs perfectly.

Paul T


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## Alex W (Nov 1, 2012)

The 9.8hp Tohatsu is a great motor. The one meant for sailboats does have a 25" shaft though, not 20", and it has a different prop (4 blades, 5" pitch). Replacing the prop is about $100, adding the alternator is another chunk of money, and then you are getting within spitting distance of the price of a new SailPro (assuming the Tohatsu 9.8 is the $800 motor in your list) and running a motor that is 40lbs heavier than what you need with an unknown history.

If you need to keep a low budget then I'd keep looking, none of these seem ideal. Borrow someone's dinghy motor for now to get you on the water.


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## Tallswede (Jul 18, 2012)

The Tohatsu's are just fine but it is Imperative that you keep the fuel fresh and clean, no water in the fuel. These little 4-strokes have very small metering jets in the carbs and will plug easily. (Ask me how I know) LOL. On the other hand, a low hour Johnson 2-stroke is about as bomb proof as an outboard gets. I too would be tempted by the Johnson even with the hassle of mixing fuel/oil. Even with the 4-strokes you need to put some stabil/water guard in the tank so mixing 2-stroke oil is not much more hassle.

Kevin


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## tschmidty (Sep 25, 2008)

The Tohatsu is $800, has a long shaft and is supposed to have a hi thrust prop already. I think it is about $125 or so to add the charging capability so it is getting up there. Probably why I am having trouble deciding!


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## Alex W (Nov 1, 2012)

The high thrust prop is easy to identify in photos, it has 4 blades instead of 3.

"Long shaft" isn't descriptive enough. There are 15" (short) 20" and 25" shafts, and 25" shafts work better on most sailboats over 20'. Both 20" and 25" shafts are often called long. I'd check with other owners of your boat to see if a 20" shaft is known to work well or if a 25" shaft is called for. I know that on both Catalina 22s and 25s that the 25" shaft is a major improvement (and it won't hurt on any sailboat).


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## tommays (Sep 9, 2008)

1. 5hp Nissan NS5B 2 Stroke. 0.7 GPH per nissan at WOT, 41lbs

The Nissan/ Tohatsu /Mercury/Evinrude are all pretty much the same motor with different paint 

IMHP one of your better picks as it is modern enough that you can get a proper prop which happens to be a 3 blade as i own one 

You have to be very carefull about older two storkes (no age is given) as it offen NOT possable to get the correct prop for a displacement hull 

9.9 is insanely BIG on a 23' boat ,really a LOT of weight on the stern and more than likely above the mounting brackets rating


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## rhr1956 (Dec 18, 2010)

I have a 2011 6HP Nissan long shaft on my Pearson 26 (5400 lbs) and it does fine unless the lake is really rough. Big waves make it tough to keep the prop in the water. AS for fuel economy...I filled up the 3 gallon tank in July. It still has a gallon or so in it. I only use the motor to leave or enter the slip.


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## MarkSF (Feb 21, 2011)

If buying a used outboard I'd get the newest I could afford. Question the previous owner about habits like flushing with fresh water, fuel stabiliser, etc.

I recently bought an 89 Yamaha 6hp 2 stroke, turns out the previous owner was unscrupulous and the engine had extensive corrosion issues leading to overheating. It's great now, after a full rebuild that included a new cylinder block! (made for an interesting project - converted it to 8hp at the same time)

2 strokes are best for short trips, as they are simple, reliable, powerful for their weight, but have horrendous fuel consumption. If you consider that a 6 hour trip, with a 2 hour fuel reserve, at full throttle on the Yamaha 8 will need 13 US gallons of fuel (6 litres per hour), the consumption does become an issue.

A new 6hp 4 stroke Tohatsu/Nissan/Mercury at full throttle uses 0.5 gallon/hour - so the same trip will need 4 gallons.


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## miatapaul (Dec 15, 2006)

I think the generalizations are going to be:

4 stroke will get better fuel economy
4 stroke will likely be a quieter

2 stroke will be lighter per HP
2 Stroke will be more reliable, not nearly as picky about fuel quality and age

Given the above I would go two stroke, and for you size boat any of these will work. My logic is it is a sailboat, so who cares about economy, what it might save a dollar or two a year or so? Most people use a few gallons of fuel a year, unless you have to motor a lot due to local conditions. Who cares about economy, what is important to me is starting. Do a search on modern 4 stokes, and you will see endless complaints of clogged fuel jets and not running after sitting a week, or even a few days.

Go 2 stroke, get a two cylinder if they make one in the horse power you are looking at, but go 2 stroke. Until they make the 4 strokes run on 10% alcohol reliably, stick with 2 strokes.


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## dabnis (Jul 29, 2007)

miatapaul said:


> I think the generalizations are going to be:
> 
> 4 stroke will get better fuel economy
> 4 stroke will likely be a quieter
> ...


Agree,

Over many years I have had 2 stroke outboards and motorcycles and properly maintained, meaning new plugs once in a while and proper oil mix, they were bullet proof after years of very hard running. The only reason I bought a 4 stroke was that 2 strokes are not allowed on Lake Tahoe, and no doubt, in the not too far distant future, any other California lake that eventually ends up in some water supply system. An extra 20 or 30 lbs hung way out over the transom is a lot.

Paul T


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## bacampbe (Mar 17, 2009)

There's not a lot left to say on this, but since I actually used to own a Spirit 23 that I got a as a hand-me-down from my parents. I'll put in a couple of comments anyway.

The previous owner had an older 6 horse 2 stroke. I don't recall the brand. My parents found that, in any chop, that was not sufficient to make them confident in handling the boat under motor if the weather went bad. In retrospect that may have been due to too short of a shaft.

Before I got it, They repowered it with a Honda 9.9 4 stroke (not on your list, of course) It made a big difference, and I didn't notice the weight causing much of a fore-aft trim issue. The motor mount was offset, and it did cause a slight list to starboard (we just moved more stuff to port to offset.) As it aged a bit, it the carb got pretty temperamental. As is common with a sailboat on a lake, we didn't go through gas fast enough to keep it clean. (For the same reason, we couldn't have cared less about fuel efficiency. Heck, it would have been better if it burnt the stuff faster.)

I originally thought that it would be nice to not have to mix oil and gas. But after changing the engine oil a few times on that heavy motor, I would have been happy to go back to mixing.


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## tschmidty (Sep 25, 2008)

Thanks for all the responses. I think I am going to go with the 9.9 Johnson 2 stroke. It is a sailmaster with electric start, alternator and the extra long shaft and sounds good, although I haven't done a sea trial yet. 

It sounds like the 5hp would be enough but I think the extra length and electric start tilt towards the Johnson. 

The 9.8 tohatsu would be great except for the extra weight and the cost of adding the alternator. With either of those the idea of hanging over the stern pulling a starter cord does not sound like fun at all.

A Tohatsu 6hp Sailpro extra long would be nice but again the manual start bothers me.

So it seems like the Johnson is a good compromise between weight, power and convienence. Parts are relatively inexpensive and it would also be fairly easy to add remote controls which would be great.

Thanks for all the responses.


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## dabnis (Jul 29, 2007)

tschmidty said:


> Thanks for all the responses. I think I am going to go with the 9.9 Johnson 2 stroke. It is a sailmaster with electric start, alternator and the extra long shaft and sounds good, although I haven't done a sea trial yet.
> 
> It sounds like the 5hp would be enough but I think the extra length and electric start tilt towards the Johnson.
> 
> ...


We had the same motor in the 15HP version, same weight and size as the 9.9HP, on our Coronado 25 at about 4,500 lbs. It was all the power we could use. We ran it hard on long trips out in the open ocean for 10 years. It was still running perfectly when we sold the boat. You WILL enjoy the electric start and 9.9HP should more than do the job. We found the synthetic oil smoked somewhat less. However, suggest you stay with the Mfr's mix ratio which was 50:1, IIRC, even if the oil Mfr says differently. I experimented with the mix ratios all over the place with 2 stroke motorcycles and finally settled back to the Mfr's spec.

Paul T


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## Sea Dawg (Jun 26, 2012)

Good choice and for all the reasons you listed. You won't be sorry with electric start or Johnson brand. Because it's a 2 stroke you'll remove it promptly when warranted as opposed to the hefty 4 strokes. Reliable, yes, but just too heavy to make me a fan.


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