Additives for small outboard petrol. Any recommendations?

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andygc

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For the third time in less than 2 years my Suzuki 2.5 has suffered a blocked jet due to the formation of little balls of fuel and water emulsion - a sticky, jelly-like material. The rather crude filter at the bottom of the fuel tank doesn't do much. After discussing this with the local engineer, who reports seeing on average 3 blocked jets in small outboards each week during the season, I'm going to fit a disposable fine filter in the tank to carburettor fuel pipe.

I had no problems whatsoever before the last three years - with either old or fresh fuel. There seems little doubt that this is a problem with the bio-ethanol content of modern petrol, resulting in the formation of water/fuel gels. I've seen adverts for additives which are supposed to triumph over water in fuel. Has anybody had any useful benefit from one of these additives, and if so, which one?
 
andygc said:
For the third time in less than 2 years my Suzuki 2.5 has suffered a blocked jet due to the formation of little balls of fuel and water emulsion - a sticky, jelly-like material. The rather crude filter at the bottom of the fuel tank doesn't do much. After discussing this with the local engineer, who reports seeing on average 3 blocked jets in small outboards each week during the season, I'm going to fit a disposable fine filter in the tank to carburettor fuel pipe.

I had no problems whatsoever before the last three years - with either old or fresh fuel. There seems little doubt that this is a problem with the bio-ethanol content of modern petrol, resulting in the formation of water/fuel gels. I've seen adverts for additives which are supposed to triumph over water in fuel. Has anybody had any useful benefit from one of these additives, and if so, which one?
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Drain the carb bowl after every use and keep the fuel in the tank fresh and you will never ever get the problem again
 
andygc said:
For the third time in less than 2 years my Suzuki 2.5 has suffered a blocked jet due to the formation of little balls of fuel and water emulsion - a sticky, jelly-like material. The rather crude filter at the bottom of the fuel tank doesn't do much. After discussing this with the local engineer, who reports seeing on average 3 blocked jets in small outboards each week during the season, I'm going to fit a disposable fine filter in the tank to carburettor fuel pipe.

I had no problems whatsoever before the last three years - with either old or fresh fuel. There seems little doubt that this is a problem with the bio-ethanol content of modern petrol, resulting in the formation of water/fuel gels. I've seen adverts for additives which are supposed to triumph over water in fuel. Has anybody had any useful benefit from one of these additives, and if so, which one?
Click to expand...

STA-BIL seems to be very popular with outboard users in the US
 
For all petrol tools (chainsaws, strimmers, hedge cutters, etc) I use premium petrol (plus oil for 2 strokes) and a dose of Briggs and Stratton Fuel Fit. In the two years I have been using it, I have not had any stoppage due to a fuel or carburation problem, OK, it has cost me about 15% more than 'cooking ' supermarket petrol, but starting is easier and the machines run well.
 
steve66 said:
Drain the carb bowl after every use and keep the fuel in the tank fresh and you will never ever get the problem again
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So when we're away from home we anchor, go ashore for a meal, come back, drain the carb, go to bed, wake up, refuel, go to the beach, drain the carb, swim and sunbathe, have a barbecue, refuel, go back to the boat, drain the carb ........
Thank you for a really helpful suggestion. That's much appreciated.
 
andygc said:
So when we're away from home we anchor, go ashore for a meal, come back, drain the carb, go to bed, wake up, refuel, go to the beach, drain the carb, swim and sunbathe, have a barbecue, refuel, go back to the boat, drain the carb ........
Thank you for a really helpful suggestion. That's much appreciated.
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Well he is right. Current fuel has a finite life in storeage and seems to turn to varnish in the fine apertures of small engines both outboards and every garden machine you care to mention. Fuel stabilisers seem to be the answer for long term storage of tank fuel. However good practice does seem to be to run your carb dry for any lay up period. After ever use would be the ideal but overkill and impractical in reality (I think steve66 is aware of that, but making a point) If I dont anticipate using an engine for 3 months or longer I run the carb dry and add stabilser to the fuel. Has worked so far for me with this so called green fuel!
 
andygc said:
So when we're away from home we anchor, go ashore for a meal, come back, drain the carb, go to bed, wake up, refuel, go to the beach, drain the carb, swim and sunbathe, have a barbecue, refuel, go back to the boat, drain the carb ........
Thank you for a really helpful suggestion. That's much appreciated.
Click to expand...

You only need to drain the carb when the engine is left long enough for some evaporation to start. If you use the engine every day then you never need to drain it. Leaving it unused for a week would be fine in the Med and probably a couple of weeks in the UK but anything longer than that and a drain down is worth doing. I've attached a short length of fuel tube to my drain which pokes down just below the outboard case. It's a 15 second job to stick my fuel can under the power head, open the screw and drain the carb back into the fuel can.

The inline filter is a great idea although it seems to get a lot of flak on here. The very small ones on eBay are dirt cheap, dead easy to fit and will ensure your carb stays dirt free. However the eBay ads are deceptive, even the 50 - 60mm long filters look small in the adverts but these were too large to fit easily in my 2.5HP Suzuki. You want the really small ones used for quad bikes and lawnmowers.

Richard
 
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Another vote for Briggs & Stratton Fuel Fit. A stabiliser that allows the fuel to remain viable for a couple of years - since I've used it for chainsaws, strimmers, and last but not least the outboard (8hp 2 stroke) I have not had any problems. I do let the outboard run dry by disconnecting the feed on each occasion that I use it but not sure if that makes much difference.
Not an expensive addition.
 
I have a 4 bhp mower and a 1 bhp s trimmer, both over 10 years old and 4 stroke and neither has ever been the slightest problem to start. I wish that I could say the same about my various outboards. Why the difference?
 
andygc said:
So when we're away from home we anchor, go ashore for a meal, come back, drain the carb, go to bed, wake up, refuel, go to the beach, drain the carb, swim and sunbathe, have a barbecue, refuel, go back to the boat, drain the carb ........
Thank you for a really helpful suggestion. That's much appreciated.
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Its no problem at all, happy to give advice any time.....
BTW its on page 21 of your owners manual regarding draining your carb after usage
 
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I know I can drain my carb.I also know that I can drain my fuel tank when the engine is not in service. I'm talking about a problem that occurs when an engine is in fairly frequent use, not when it is stored for months. Draining the carb does not prevent fuel from emulsifying in the bottom of the fuel tank, and draining the carb has no effect whatsoever on sticky droplets of emulsified fuel and water getting into the carb when the engine is running.

My question was not about draining anything, or asking for advice on how to read my owner's manual. It was about the effectiveness of fuel additives in preventing emulsification. If you have nothing to say on that subject, please say what you want to say in another thread.

To those who answered the question I asked, thank you, your help is appreciated.
 
andygc said:
I know I can drain my carb.I also know that I can drain my fuel tank when the engine is not in service. I'm talking about a problem that occurs when an engine is in fairly frequent use, not when it is stored for months. Draining the carb does not prevent fuel from emulsifying in the bottom of the fuel tank, and draining the carb has no effect whatsoever on sticky droplets of emulsified fuel and water getting into the carb when the engine is running.

My question was not about draining anything, or asking for advice on how to read my owner's manual. It was about the effectiveness of fuel additives in preventing emulsification. If you have nothing to say on that subject, please say what you want to say in another thread.

To those who answered the question I asked, thank you, your help is appreciated.
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Sorry I couldnt be of any more assistance to you Andy. I have very little knowledge with small outboards carbs and fuel but I thought I would offer the very limited knowledge I have.
 
Lots of incorrect knowledge here. I worked for years in the petrol and testing industry.

1. Draining is mostly myth. Unless you get every drop, that only makes sure it turns to gum. Unless for more than 3 months, leave as-is.
2. Close the vent on the integral tank EVERY TIME you are not running the engine. A single rainy night can splash in a fatal amount of water. A week of high humidity can breath it is. These are very small tanks.
3. The gum/gel is not from fuel break down, it is from aluminum corrosion. Aluminum hydroxide makes gels that are great for clogging stuff. Carbs have both brass and aluminum, which is bad. Close the vent to keep the gas dry, and use an anti-corrosion additive. Merc Store-n-Start is good. Also Biobor EB. Most are not very helpful. Any that combine water will make corrosion worse.
4. Adding a filter is smart and easy.
5. No, the fuel does not have a short life. It is good for years (I have tested out to 5 years) if you store it properly. That means no air, no water. But it does not just "go bad." That is myth. However, since contamination is always possible, run the engine enough to use it up every 2 months. Easy.

So... Close the vent every time and use Biobor EB. No problems.
 
I used to be with BP on the aero side, where fuel cleanliness is above godliness.

BP Australia has a particular problem with air/sun temperature on the tanks, plus a robust attitude towards fuel hygiene, with very fine particles of bio-active dust causing problems.

A couple of papers

http://www.bp.com/content/dam/bp-country/en_au/media/fuel-news/petrol-life-vehicle-tanks.pdf

http://www.bp.com/content/dam/bp-country/en_au/media/fuel-news/long-term-storage-diesel.pdf

noting storage and atmospheric problems.

Fuel sealed in steel cans has a long life as TW notes. Storage in Antarctic bases is often for 3 years in bulk tanks in case of re-supply problems.

A quick check on the Biobor MSDS reveals a slightly worrying comment that the product may attack some plastics, rubber and coating. I'll try and find out more.
 
Thank you thinwater and sarabande.

I do close the vent, and I've a waterproof cover for the motor when it is on an outdoor rack ashore. The owner's manual for the Suzuki 2.5 does not recommend running the carburettor dry when stopping the engine (I rechecked), and I don't do it.

The gum/gel is not from fuel break down, it is from aluminum corrosion. Aluminum hydroxide makes gels that are great for clogging stuff.
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That makes sense. I was told it was bio-ethanol+water emulsifying that created the problem, but presumably the corrosion follows on from that. There's certainly evidence of corrosion in the bowl. I can't help but think that bio-ethanol is at the bottom of the problem as I never had any trouble with blocked jets before it started to be added to petrol.
Any that combine water will make corrosion worse.
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And that also makes sense.


sarabande, I would certainly be grateful to know if there are any potential problems with BioBor.
 
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