Outboard: Carburetor vs EFI

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dw8928

dw8928

Senior Member
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162
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Silver
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Helmsman 31
Anyone have an opinion about a 20hp outboard having a carburetor (Tohatsu for instance) vs EFI (Yamaha)? Seems to me that, eventually, fuel will have a chance of going sour (ethanol included) and gum things up.

A carburetor can be opened and cleaned with some simplicity. An EFI is much more complicated and expensive to repair - especially if the injectors need replacing.

Wrong assumptions?
 
EFI keeps the gas isolated from oxygen while in standby, system is completely sealed up. EFI engines can sit for six months then start like they ran yesterday. Carbs always have fuel exposed to air in the bowl. Leave it sit six months and you are going to need tools.
 
EFIbis also much more fuel efficient in the metering of the file across the entire power band.
 
I've had plenty of 2 cycle carburetor o/b's over decades for dinks and runabouts. Currently have a great 1975 50 hp Johnson on our Crestliner 14'8" tow behind, four seater runabout. I simply add about 1/8 pint Berryman B-12 Chemtool to every 6 gal tank fill-up.

https://www.berrymanproducts.com/pr...-carburetor-fuel-system-and-injector-cleaner/

Never have problem... even after six months or longer of no use. I do recommend always off hooking the pressure line from gas tank and at engine each time of dormancy.
 
With either system, I disconnect the fuel line and run the system dry of fuel after use. Never had an issue with fuel going bad in either type of motor.

Ted
 
One can work around the air police bad gas requirement in many areas where non ethanol fuel is available.
 
EFI- As others have said, more efficient, quicker start as you do not have to refill carb bowl, resistant to ethanol damage. Go for EFI!!!


David
 
I have a 6hp Tohatsu with carb for my dingy and am now very proficient in dismantling the carb since I have had to do it so many times. As Ted has stated, I now disconnect the fuel line and let it run dry each time I use it and that seems to have solved the issues. On my 20 HP Yamaha EFI I just shut it off and if I don't use it for a month or two it doesn't matter, it just starts right up. I would not buy another carbed engine just to save a few bucks.
 
O C Diver said:
With either system, I disconnect the fuel line and run the system dry of fuel after use. Never had an issue with fuel going bad in either type of motor.

Ted
Click to expand...

I've found that by adding 1/8 pint Berryman B-12 Chemtool to every 6 gal tank fill-up (will admit I miss adding it now and then) there is no need for running dry. Have had carbureted o/b engines sit for many, many months with quick restart being no problem. As with all carbed o/b's, once both ends of fuel line are reconnected - primer bulb in line needs to be squeezed until firm resistance is accomplished and then choke used appropriately. Basically the exact same fuel primer / choke process used for multi month dormancy as for over night shut down that cools engine completely.


BTW - I've also found that by utilizing Chemtool in gasoline idle is smooth. :thumb:


PS: Upon reading my two posts regarding Berryman B-12 Chemtool in gasoline... I forgot to mention the following. Sometimes (about every 4th to 6th six gallon tank fill-up I'll throw in about 1/2 pint Chemtool to really help keep fuel line internals clean! That's about the maximum recommended amount of Chemtool to add to gasoline - by %age.


This video is clearly eye-opening...


 
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Art- Did you not used to plug "Startron" additives? Why the change to start plugging "Chemtool"?

To the OP- go EFI and if you can, get a three cylinder. Two's are rough running. Wish they made tiny four stroke three's like 10-15hp.
 
Ski in NC said:
Art- Did you not used to plug "Startron" additives? Why the change to start plugging "Chemtool"?

To the OP- go EFI and if you can, get a three cylinder. Two's are rough running. Wish they made tiny four stroke three's like 10-15hp.
Click to expand...

Ski - I consistently use and recommend Soltron, instead of Startron.

Soltron and Chemtool are completely different animals.

Soltron is for keeping fuels clear of "bugs" as well as emulsifying water into a fuel substance that mixes into (becomes fungible with) fuels in tank while virtually eliminating separation factors of E-Fuels. I always add that in my Tolly's 100 gallon tanks when fueling. It enables keeping gasoline/diesel really clean with ability to sit idle for up to years if necessary without turning bad.

Chemtool is for dissolving deposits off interior walls and other surface areas of fuel lines.


Tolly's 200 gallon fuel may last for some time before 100% change happens, if it ever really does... at best it is intermixing with old and new. O/b six gallon tank drains often to empty with all-new fuel at replenishment.
 
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DW8928-yup, wrong assumption. Some folks put "mouse milk" in their gasoline outboard fuel. Many swear by this solution. I have owned carbureted outboard engines (2- and 4-cycle) for some 50 years now, only use non-ethanol gasoline, and have religiously run my carbureted outboard motors dry after every use. No mouse milk, however. While this technique has prevented issues with blockage of the fuel system, it has NOT prevented issues with the routine need for adjustment, priming, cleanout, "fiddling", and other associated ills with carbureted outboards.

And by the way, ditto the above for my lawn mowers, weed eaters, pressure washers, etc. that I use on dry land. Interesting that many dealers for industrial and consumer land-based small engine products (Stihl, for example) now offer single-use non-ethanol cans of premix for their 2-cycle carbureted engines. Carbureted engines that sit unused for long periods of time are simply a PIA.

My latest outboard (30hp Tohatsu) is EFI. WAY better fuel system than on ANY previous carbureted outboard to date. Easier to start, better fuel economy, better idle, better throttle respone, blah blah blah. And there are many very real (and non-pollution related) technical reasons why most all modern internal combustions engines are now fuel injected. In my opinion (YMMV), fuel injection is the correct choice for any outboard powered boat. Hopefully this technology will percolate down to the lower-powered outboards soon, so ALL can take advantage of it.

Regards,

Pete
 
I've been told that Tohatsu has developed an EFI for under 25hp OBs but that they are relentlessly testing the system before release - supposedly still a few years away apparently.

jungpeter said:
DW8928-yup, wrong assumption. Some folks put "mouse milk" in their gasoline outboard fuel. Many swear by this solution. I have owned carbureted outboard engines (2- and 4-cycle) for some 50 years now, only use non-ethanol gasoline, and have religiously run my carbureted outboard motors dry after every use. No mouse milk, however. While this technique has prevented issues with blockage of the fuel system, it has NOT prevented issues with the routine need for adjustment, priming, cleanout, "fiddling", and other associated ills with carbureted outboards.

And by the way, ditto the above for my lawn mowers, weed eaters, pressure washers, etc. that I use on dry land. Interesting that many dealers for industrial and consumer land-based small engine products (Stihl, for example) now offer single-use non-ethanol cans of premix for their 2-cycle carbureted engines. Carbureted engines that sit unused for long periods of time are simply a PIA.

My latest outboard (30hp Tohatsu) is EFI. WAY better fuel system than on ANY previous carbureted outboard to date. Easier to start, better fuel economy, better idle, better throttle respone, blah blah blah. And there are many very real (and non-pollution related) technical reasons why most all modern internal combustions engines are now fuel injected. In my opinion (YMMV), fuel injection is the correct choice for any outboard powered boat. Hopefully this technology will percolate down to the lower-powered outboards soon, so ALL can take advantage of it.

Regards,

Pete
Click to expand...
 
FWIW - Berryman B-12 Chemtool is:


45-50% Toluene
20-25% Acetone
20-25% Methanol
Plus trace solvents
 
Ski in NC said:
Art- Did you not used to plug "Startron" additives? Why the change to start plugging "Chemtool"?

To the OP- go EFI and if you can, get a three cylinder. Two's are rough running. Wish they made tiny four stroke three's like 10-15hp.
Click to expand...

I've always wished for a small multi-cylinder OB. Had the same thoughts. But they would be heavier, burn more fuel and make less power unless rev'ed higher like 7-8000rpm. In my motorcycling days I learned lots of cylinders made engines that were flat on power and even more so on torque. The 350 honda 4 was heavy and slow whereas the twins were great. In the days though I rode Suzuki 2 stroke twins. Very light and very fast.

Think 2 stroke 2 cyl like my 4hp "Light Twin" OMC. With one of those angle drive lower units. Very smooth and relatively quiet w the FG cover. Note that a 2 stroke twin has the same # of power strokes as a 4 stroke 4 cyl. I just reciently got my third one. The first two were hopelessly salted. This little 4 seems OK. Only 32lbs too.

As to the OP all the above is true to my knowledge but small carbuated engines seem OK if given special treatment. One huge difference though is that you can fix a carb engine.
 
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I think that is the BIG advantage of a carb - the ability for self help almost anywhere. I would be lost on an EFI. Plus the injectors are expensive.

Nomad Willy said:
I've always wished for a small multi-cylinder OB. Had the same thoughts. But they would be heavier, burn more fuel and make less power unless rev'ed higher like 7-8000rpm. In my motorcycling days I learned lots of cylinders made engines that were flat on power and even more so on torque. The 350 honda 4 was heavy and slow whereas the twins were great. In the days though I rode Suzuki 2 stroke twins. Very light and very fast.

Think 2 stroke 2 cyl like my 4hp "Light Twin" OMC. With one of those angle drive lower units. Very smooth and relatively quiet w the FG cover. Note that a 2 stroke twin has the same # of power strokes as a 4 stroke 4 cyl. I just reciently got my third one. The first two were hopelessly salted. This little 4 seems OK. Only 32lbs too.

As to the OP all the above is true to my knowledge but small carbuated engines seem OK if given special treatment. One huge difference though is that you can fix a carb engine.
Click to expand...
 
jungpeter said:
In my opinion (YMMV), fuel injection is the correct choice for any outboard powered boat. Hopefully this technology will percolate down to the lower-powered outboards soon, so ALL can take advantage of it.
Click to expand...

dw8928 said:
I've been told that Tohatsu has developed an EFI for under 25hp OBs but that they are relentlessly testing the system before release - supposedly still a few years away apparently.
Click to expand...


The newer Suzuki 9.9/15/20 models are fuel-injected. So far, our DF15A seems to be dealing with the ethanol we get around here better than our 2-stroke carbureted outboard.

-Chris
 
One of the reasons for running the fuel out in a 2 stroke was that if you didn't, the gas would evaporate leaving behind the 2 stroke oil. While not impossible to start the next time, it was easier without the oil residue. Back when I had a gasoline powered truck, I would empty the 6 gallon boat fuel tank into the pickup tank and start with fresh fuel each boat outing. Still have a 2 stroke Mercury 6 HP. Run it on ethanol free gas and Mercury 2 stroke oil, no snake oil. Still going strong after 30 years.

Ted
 
Go EFI. I had a Yamaha F40 carb motor that one year I made the mistake of forgetting to winterize the fuel system(10% Ethanol here in NJ). It got to the point that I could remove, disassemble, clean, and re-assemble the 3 carbs in less than 2 hours flat because just the slightest speck of dried gas crud would clog the low speed jets. It would run fine for maybe an hour before another speck would find its way to the jet again. Thankfully it was almost always the bottom carb which was the easiest to get to the culprit.
On my 5 hp Tohatsu 4 stroke, you can remove the low speed jet for cleaning without disassembly. Just takes a couple minutes.
 
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For years I ran my ethanol run 4 stroke out of gas...no issues....first time I forgot to for 4 months.....clean the carb big time.


I am no mechanic...but based on how many people I towed....additives are pretty much snake oil, using an outboard without running it dry if full of ethsnol...a crap shoot, run it dry, no problems. My experience backs that 100 oercent.

2 strokes a different animal....

If the mechs say injection is less likely to foul...that's the way I would go...and learn the few tricks to get them going when they don't start.
 
Imagine if cars still had carburetors? No thanks , have one hot rid left with carbs and its always taking attention that I have never seen in any of the fuel injected engines since those early days. Go fuel injections for sure...
 
O C Diver said:
With either system, I disconnect the fuel line and run the system dry of fuel after use. Never had an issue with fuel going bad in either type of motor.

Ted
Click to expand...

This my operation procedure. As to choice, EFI every time, However in my case, I purchase old O/B 2 strokes because of use in hours vs cost. Purchasing a new 6 hp 4 stroke can run around $2500 plus or minus, where as I can located and purchase a little used 6 hp Evenrude or Johnson for anywhere between $300-600 dollars. (Craigslist).
My 'Git-a-Home' OB is an older four stroke 9.9 Yamaha with carb. given an opportunity a replacement (used) would be EFI. Still, I would run the fuel supply hose dry on shutting down.
It is the corn in the standing gas that causes the grief.

Al-Ketchikan 27' Marben Pocket Cruiser
 
Depending on how far away from a repair facility I will be would make the decision. We had a newer 4 stroke efi suzuki on the one nordhavns I have cruised on...and had issues with it from califonia to florida.. if it had been a carbed motor I have no doubt I could of fixed it..the efi motor I never could get right. They are very fuel sensitive. I always keep a eye open for good condition yamaha 10/15 hp freshwater use motors to use a dinght motors as they are dead reliable. I had one thst was sunk in salt water 20' deep overnight.. flushed it out and ran it for a additional 10 years...try that with a efi motor!

If staying domestic.. efi motors are great and fuel effecient. Service isnt far away so the issue of having it worked on becomes no problem.
Hollywood
 
I would normally agree.....but this last time, my yammie 8hp 4 stroke required 3 cleanings in an ultrasonic cleaner.

I had dismantled ir 5 times with the same poor idle..only the cleaner and special sauce got her working.

Without access to an ultrasonic cleaner...that carb wouldn't respond so it could have been fuel injected with the same negative rexponse.
 
psneeld said:
I would normally agree.....but this last time, my yammie 8hp 4 stroke required 3 cleanings in an ultrasonic cleaner.

I had dismantled ir 5 times with the same poor idle..only the cleaner and special sauce got her working.

Without access to an ultrasonic cleaner...that carb wouldn't respond so it could have been fuel injected with the same negative rexponse.
Click to expand...

My Yamaha 9.9 4-stroke was the same way. Numerous carb clean/rebuilds, finally a new carb. Lots of excuses from the dealer and repair guys about 'tiny' jets and passages. I got rid of it. I now have a 2-stroke Evinrude 9.9 that starts instantly, is lighter and faster.:D
 
So I think I can boil down the consensus:

Little motors like 6-15, go carb two stroke.

Larger motors like 25up, if you want to go four stroke, go three cyl and EFI.

15-25 is a grey area. Gas mileage advantage of a four stroke over a two stroke get a bit more important here than on the little ones. Just avoid the four stroke two cylinders there, big and rough, but too small I think for anyone to make a three cyl. On my dock is a new merc 30, it's a EFI three and runs real nice. Think it a relabled Tohatsu.

If you are venturing far and wide with sketchy fuel supplies, a Yamaha Enduro carb two stroke is the way to go. Just can't buy them stateside. May have to wait til you get to your first foreign port of entry.
 
Ski in NC said:
So I think I can boil down the consensus:

Little motors like 6-15, go carb two stroke.

Larger motors like 25up, if you want to go four stroke, go three cyl and EFI.

15-25 is a grey area. Gas mileage advantage of a four stroke over a two stroke get a bit more important here than on the little ones. Just avoid the four stroke two cylinders there, big and rough, but too small I think for anyone to make a three cyl. On my dock is a new merc 30, it's a EFI three and runs real nice. Think it a relabled Tohatsu.

If you are venturing far and wide with sketchy fuel supplies, a Yamaha Enduro carb two stroke is the way to go. Just can't buy them stateside. May have to wait til you get to your first foreign port of entry.
Click to expand...

Ski - I looked up Yamaha Enduro. Sounds good; thanks for posting.

Still, regarding my decades of exceptional-luck with gool ol' Johnson and Evinrude 1960's thru 1990's two strokes (3 hp to 100 hp)... buck for buck, mileage for mileage, simplicity for simplicity, longevity for longevity - well you get the picture.

1975 50 hp. Johnson that we've had powering our Crestliner runabout for seven years has needed only a new starter, low-end fluid change, one tune up, and a couple new impellers. As with all the others I've owned... this little mid range hp. Johnson o/b is a joy to own and use.

BTW - Tuned-up and carb adjusted correctly she runs smooth at idle and through its full range to WOT. :thumb:
 
That 50hp OMC two cyl looper was a neat motor in a few ways. My Dad had one that replaced a Merc 50 4cyl and the gas mileage improvement was incredible. We needed two six gal cans to do our thing with the merc. Once we got confident with the OMC, we just carried one and did the same thing. Quiet and faster than the merc, but the merc was 20yr old at the time and she was feeling her age.

The OMC finally died, but not the motor. It was the power trim system that was really a POS from the start. Bad design. But the motor was still doing fine when traded in. Without power trim, it would have lasted much longer. But as a flats skiff, PT is God!!
 
Ski in NC said:
15-25 is a grey area. Gas mileage advantage of a four stroke over a two stroke get a bit more important here than on the little ones. Just avoid the four stroke two cylinders there, big and rough, but too small I think for anyone to make a three cyl. On my dock is a new merc 30, it's a EFI three and runs real nice. Think it a relabled Tohatsu.
Click to expand...


Our Suzuki 15 is 4-stroke, EFI, 2 cylinders... runs fairly decent. Almost silent at idle, a bit of vibration at slow speeds, smooths out better at slightly higher speeds. We haven't run it much, though, since we lost our pooch...

-Chris
 
Ski in NC said:
That 50hp OMC two cyl looper was a neat motor in a few ways. My Dad had one that replaced a Merc 50 4cyl and the gas mileage improvement was incredible. We needed two six gal cans to do our thing with the merc. Once we got confident with the OMC, we just carried one and did the same thing. Quiet and faster than the merc, but the merc was 20yr old at the time and she was feeling her age.

The OMC finally died, but not the motor. It was the power trim system that was really a POS from the start. Bad design. But the motor was still doing fine when traded in. Without power trim, it would have lasted much longer. But as a flats skiff, PT is God!!
Click to expand...

Our fairly deep V mono hull Crestliner has stationary-set (yet mechanically adjustable) trim tabs on her. With them as well as the o/b's pin-trim set in good position the Johnson o/b and boat complement each other flawlessly. Where in... getting on plane is really quick and the boat cruises at correct trim/angle during all rpm. There is no power trim. The engine and boat are still almost like new. They were an original matched pair in 1975. 14'8" Crestliner "Stinger" only weighs about 400 lbs. Top speed is 39.5 knots with just me. She cruises all day at a gentle lope of 25 knots with both Linda and me. I calculate at that gentle speed she gets 21 nmpg +/-. For use in SF Delta's relatively calm fresh waters she's a great tow behind runabout we take everywhere we go.
 

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