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Outboard Fuel Questions

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michaelj
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132 Posts

Initially Posted - 06/03/2013 : 06:27:58

I just got a new Tohatsu outboard. In my old Yamaha I had a lot of trouble with the motor gumming up. I ascribed this to ethanol in the gas and the fact that I only start the motor about twice a month. I want to avoid that with my new motor. So I have some questions:
(1) I can get gasoline free of ethanol. Should I use this? (2) I have read that a water separating filter in the fuel line is a good idea. (3) What is the best additive to put in the gas? (4) When I'm getting ready to leave, should I disconnect the fuel line at the motor and run the motor until it stalls? Thanks.

Edited by - on

Davy J
Master Marine Consultant

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USA
1511 Posts

Response Posted - 06/03/2013 : 06:49:59

You're probably going to get a few different opinions on this. When I got a new Tohatsu about 4 years ago, I would just run the motor, then when finished for the day, I would flush it out. But not run it out of fuel. I also left the fuel line and tank onboard until the next trip out. After needing to clean the carb, twice, within 6 months I have a new routine.

I disconnect the fuel line and flush the outboard until it runs out of gas. I also take the fuel line and tank off the boat. I also now drain the fuel, that sits in fuel line, out, before using the fuel line and tank again. It maybe overkill, but I haven't had to clean the carb since.

ETA: I use mid-grade fuel and don't use additives.

Edited by - Davy J on 06/03/2013 06:51:50

redeye
Master Marine Consultant

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3476 Posts

Response Posted - 06/03/2013 : 06:55:38

Yes ( eth free )

Yes ( fuel filter always a good idea )

seafoam .. or any others. ( I can't recomment any one addative, they are all good )

not sure ( runn out engine )

I'm not sure how the running the fuel out thing works on 4 strokes, but we did not have any luck with that on a "non-premix" 2 stroke engine. the engine would keep running on the oil. We did do that on regular 2 strokes.

Edited by - redeye on 06/03/2013 06:57:33

GaryB
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USA
4311 Posts

Response Posted - 06/03/2013 : 17:49:30

Definitely go with ethanol free if you can get it along with a fuel filter.

Sea Foam has always done a good job for me.

I always run my oil injected 2-stroke out of gas. Disconnect the fuel line at the tank if you can. As the motor is running, occasionally (every 10 seconds or so) depress the little ball valve in the tank end of the fuel line to "vent" the line so it can burn all of the fuel out of the fuel line.

After my motor dies I pull the choke out and re-start it 4 or 5 times in an effort to get all of the fuel out of the carb. Also helps to run the motor at a medium idle speed to help get all of the fuel out of the carb. Low idle doesn't seem to get all of the fuel out.

Never had any problems with it running on the oil.

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 06/03/2013 : 18:10:44

Like said, you're going to get lots of opinions here, but here's my take after going through a phase separation nightmare a couple of years ago that continues today.

If I can find it, I buy zero ethanol gas, there's just too much that goes wrong with E10/E15 fuels on our boats because we simply don't run a lot of fuel through them.

I use a Racor fuel/water separator. It seems like overkill to me, but I never-ever want to go through the pains I went through with my outboard & fuel system, and particularly do not want to ever have to be towed in again for what I see as a preventable problem.

I never used to worry about running the engine out of fuel after each sail, and I'm still on the fence on this idea.

I've used Sea Foam, Stabil (marine & regular), Startron, and a number of other things to attempt to keep the fuel working properly on my engine. My take is that they're all probably not much more than expensive kerosene/turpentine/other solvent with various results, and most exist due to the problems introduced with E10 fuels.

If I were going to choose only one of these, it'd be use E0 fuel if you can find it.

You've bought a good engine in my opinion, our Tohatsu has never given us any problems that weren't preventable or not it's fault.

Edited by - on

GaryB
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4311 Posts

Response Posted - 06/03/2013 : 19:08:47

Do you guys close the vent on your tanks when you leave the boat? Maybe it's just a difference in the climates but I've never had any problems with fuel in the 40+ years I've been boating.

If the gas in my tank sits 2 months I dump it in the car and put fresh fuel in. I've always run my outboards dry when done using them and I've never had to have a carb rebuilt.

Now that I've said all of the above I'm quite confident all of the above will happen shortly.

Edited by - on

Stinkpotter
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Djibouti
9082 Posts

Response Posted - 06/03/2013 : 19:23:29

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by GaryB
 Do you guys close the vent on your tanks when you leave the boat? Maybe it's just a difference in the climates but I've never had any problems with fuel in the 40+ years I've been boating.

If the gas in my tank sits 2 months I dump it in the car and put fresh fuel in. I've always run my outboards dry when done using them and I've never had to have a carb rebuilt.

Now that I've said all of the above I'm quite confident all of the above will happen shortly.
<hr height="1" noshade id="quote"></blockquote id="quote">Yup! You're toast now!

Closing the vent is important. As the tank cools at night, it inhales damp air. Some moisture condenses on the inside of the tank and runs to the bottom, and the ethanol absorbs some. If the ethanol/water concentration reaches a saturation level, the ethanol "drops" the water the next time the temperature drops.

The next thing that's important, then, is to remember to open the vent!

Edited by - Stinkpotter on 06/03/2013 19:25:23

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 06/03/2013 : 20:07:11

My "new" OMC tank is self venting, so after I fill it with gas I simply screw on the filler cap and forget about it. What I don't know is how it's self venting affects the breathing cycle Dave is referring to. Since I don't have a gasoline powered vehicle (all mine are diesels), I don't have the option of dumping my aging fuel into a car and using it. I suppose I could give it to a neighbor or something, but most are reluctant to take it, and even our gardeners don't want it for their lawn equipment. Can't say I blame them, there's almost nothing I hate more than working on a grumpy small gasoline engine, and I'd imagine that's a fairly common sentiment.

Edited by - on

CarbonSink62
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208 Posts

Response Posted - 06/04/2013 : 07:09:58

I use SeaFoam in my first tank of the year to dissolve any gumminess that might have been created during storage.

I mix Stabil (a little heavier than they say) with every tankful.

I try (really hard) to run my engine at least once a week.

So far so good.

I never close my tank vent. I understand the issue and I believe it; but I think it is a problem for boats that sit a long time. I also try to run my tank as dry as I can before I add more gas.

Edited by - on

JohnP
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1520 Posts

Response Posted - 06/04/2013 : 08:09:44

The problems with water in the gasoline are related to its exposure to humid air. I found water separation from the gas in my old fuel tank, due to varying, sometimes week or month-long periods between uses and storage of the fuel tank in the humid environment on the boat, and also due to cracks in my fuel tank and leaks in my fuel line or bulb.

Since changing my standard operating procedure for the 4-stroke Honda 9.9, my motor has always started on the first pull (preferred to electric starting) and has run flawlessly for 2 summers and a spring season.

Here's what I have done:
- New tank
- New fuel line
- When 1 minute from docking in the slip, remove fuel line from outboard to give about 2 minutes more run time at the dock
- After docking, stop engine
- Lift engine out of the water vertically
- Hook up fresh water hose to the flush adaptor tube on the engine
- Run the water
- Start the engine and run until engine stalls and water pump and cooling system are flushed
- Optional step - Opening the carburetor drain screw to collect another teaspoon of fuel out of the drain tube into a paper towel
- Stop the water flow and stow the flush adaptor and hose
- Keep the outboard out of the water until next use
- Dispose of the remaining gas in our car
- Buy fresh gas for each sailing trip

Results: No annual impeller failures like previously, and no persistent problems with water in the gas yielding poor engine performance like before.

I guess some locations may not have hot days and cool nights like here, and so the gas may not get wet like it does at my marina. If you have ready access to E-zero gas that could solve the problem of wet gas and water separation. Also, if you happen to use your outboard each day, then these problems may not be significant. The fuel additives deal with carbon, varnish, and gum deposits in the engine cylinders, but not with water clogging up the jets or wetting the spark plugs, and I don't need to clean the engine or stabilize the fuel when using this procedure.

I am so relieved to now have reliable outboard performance!

Happy sailing to all!

Edited by - on

OLarryR
Master Marine Consultant

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USA
3473 Posts

Response Posted - 06/04/2013 : 09:18:34

All great suggestions: Racor water/fuel separator, additive, keeping vent closed when done motoring.

A biggy is how often you use the outboard. I do not have a water/fuel separator but i also rarely have a period longer than a week even in the winter time that I have not used the outboard. Okay - maybe in the winter I have had a period of perhaps two weeks when I have not used the outboard but I also tend to keep the fuel tank filled to the max or at least 3/4 filled especially during those times when I am not using the outboard for a couple of weeks or so. So, I use the outboard often and with every tank fill up I either add Startron or Stabil. Also, many run the outboard dry when they do not use the outboard for a period of time, so that the outboard's gas line and passages do not either have deposits/gunk forming in it or water. But since I frequently use my outboard, I do not run the gas out. In the winter, when I raise my outboard, I will pull the cord/start the outboard momentarily to fling any water that is on the impeller off of it, so that it does not freeze and become an issue the next time I go out and temps are...cold outside where there is a possibility that any water around the impeller could have frozen to it overnight. So far, I have never had an issue with my outboard.

Edited by - on

Jay Schkloven
1st Mate

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USA
84 Posts

Response Posted - 06/08/2013 : 08:49:15

I have been the same route with the motor, Tohatsu 9.8. I only use the motor to get out of the marina and into the river. Then back again. Maybe 6 miles. I refill the tank with fresh fuel each time and use Starton and Stabil. I only put in 1.5-2 gallons into the tank because the motor really sips fuel. If I am not going to use the boat for more than two weeks the fuel goes into the car and new is added. I refill another 2 gal. tank and keep it on board each time I go out. This allows for the need to maybe travel a longer distance.
Thank you big government for creating another issue. My Congressman did not help when I made a suggestion for summer E0 boat fuel in Baltimore Co.

Edited by - on

Stinkpotter
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Djibouti
9082 Posts

Response Posted - 06/08/2013 : 09:04:52

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by CarbonSink62
 I never close my tank vent. I understand the issue and I believe it; but I think it is a problem for boats that sit a long time. I also try to run my tank as dry as I can before I add more gas.<hr height="1" noshade id="quote"></blockquote id="quote">What I've been told (and it makes sense to me) is the more air you have in the tank, the more "breathing" and condensation you're likely to have, and that condensation accumulates in the bottom, under the gas. The open vent also promotes gasoline evaporation, which cools the gas and promotes water condensation. Therefore, the recommendations are generally to keep the tank as full as is reasonably convenient--at least till the end of the season when you dump it into your vehicle--and close the vent.

I suspect it's unreasonable to expect E-0 gas to be available in most places, since it requires separate transportation and storage of a fuel that cannot be sold legally for motor vehicles. A few sailors might be willing to pay the premium, but not most $+!nkp*++ers. And you have to wonder about the octane.

Edited by - Stinkpotter on 06/08/2013 09:06:25

islander
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USA
4024 Posts

Response Posted - 06/08/2013 : 11:21:14

Although I totally agree with Dave I also believe that most of the outboard/gas problems that some of the members here have is due to the infrequency that there boat is used. You can't expect today's gas to sit in a carb or tank for a month or more and expect that everything will be OK. This said I do not close my vent and never have I had a fuel/carb issue but I use my boat 2-3 times per week and sail between 800 to 1100Nm. per season and use about 2-3 Gal per month. Steel gas tanks, Get rid of them. Replace your fuel line on a timely basis. Just run of the mill common maintenance will go a long way to having a trouble free season.

Edited by - on

cat25
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USA
140 Posts

Response Posted - 06/09/2013 : 03:57:47

I use pri-g gas treatment for many years with great results. Many fisherman use pri-g that's how I found out about it Ken.

Edited by - on

pastmember
Master Marine Consultant

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2402 Posts

Response Posted - 06/09/2013 : 12:24:35

Anyone like Seafoam fuel treatment.

Edited by - on

michaelj
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132 Posts

Response Posted - 06/09/2013 : 13:57:11

Thanks for the very informative responses. I bought a water separating filter and am going to try to use ethanol free gas. Now I have another question. My old outboard had a plug for the battery connection mounted on a bulkhead between the fuel and sail lockers. My new one just has the lugs on the end of the battery cable. I am thinking about taking one of my two batteries out of the cabin and putting it in a battery box in the fuel locker and just hooking the lugs on. Does anyone see any problems with that? Thanks.

Edited by - on

cat25
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USA
140 Posts

Response Posted - 06/10/2013 : 07:11:15

I would not mix battery vapors with gas vapors . Sounds like a recipe for something volitle. Ken

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