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thomm225 · 28-08-2013, 10:33

It looks like the 5hp Nissan/Mercury has a large carburetor than even the 4 hp outboard so maybe this is a difference maker between those that are having problems with the smallest outboards

fjwiley1 · 28-08-2013, 11:15

I too have the "Nissan" but in a 6 HP. Great engine. Like all have mentioned "run it dry of all the gas when shutting down or it will "gum" up". Gumming is not the problem....
No one has mentioned the true culprit and that is Ethanol. Ethanol is now part of all gasoline refining and it induces moisture. If you have the opportunity, don't by gasoline containing Ethanol for any small engine whether it is a "weed eater, blower, lawn mower or dingy engine". Pay the difference in price at the pump, if available, and save a lot of frustration. Fortunately the marina next door to me has Ethanol free gas and good Marine Diesel fuel. Ethanol in gas....bad for any marine use.

MarkSF · 28-08-2013, 11:26

I disagree... it IS gumming up and it would happen regardless of whether the gas has ethanol in it. Gasoline simply leaves a residue when it evaporates. This residue affects any vehicle.. that's why your car's fuel injectors lose efficiency over the years.

The problem with small 4 strokes is that the passageways and jets are very small so they can get blocked up much more quickly.

You can use ethanol gas just fine... I've been doing so for years. Just use a stabiliser and keep the gas fresh.

Ethanol does not INDUCE moisture. It absorbs it. The moisture has to be there in the first place. As many studies have pointed out, it might be preferable to have moisture in solution in the gas, than to have it separated at the bottom of the tank.

Lake-Effect · 28-08-2013, 11:27

Quote:

Originally Posted by fjwiley1

No one has mentioned the true culprit and that is Ethanol. Ethanol is now part of all gasoline refining and it induces moisture. If you have the opportunity, don't by gasoline containing Ethanol for any small engine whether it is a "weed eater, blower, lawn mower or dingy engine". Pay the difference in price at the pump, if available, and save a lot of frustration. Fortunately the marina next door to me has Ethanol free gas and good Marine Diesel fuel. Ethanol in gas....bad for any marine use.

This has been my mantra... I only buy ethanol-free gas, I always use fuel stabilizer, and at the end of the season I dump any remaining boat gas into the truck, and buy fresh gas in the spring.

Caveat - our engine is a '83 Suzuki 5 HP 2-stroke. I don't run the carb dry. After a few seasons I disassembled the carb just to look, and it was clean as a whistle - no gum, no deposits, just a small amount of still-liquid two-stroke oil.

Assuming 2-strokes may ultimately be banned, I'd be interested in hearing from more 4-stroke outboard owners who run only ethanol-free gas, to find out if they have less problems than others.

PS - anyone make a decent small diesel outboard, yet?

MarkSF · 28-08-2013, 11:31

So... you buy ethanol-free gas, but add the fuel stabiliser anyway, and then don't do the single most important thing you can do.

I ran a 4 stroke with ethanol gas and had no problems. How can you have less problems than that?

Lake-Effect · 28-08-2013, 11:42

Quote:

Originally Posted by MarkSF

So... you buy ethanol-free gas, but add the fuel stabiliser anyway, and then don't do the single most important thing you can do.

As I just said... it works for me. 7 years of intermittent seasonal use, no carb teardowns required. I did say it was an older 2-stroke... perhaps if I had a newer 4-stroke, I would have a different experience.

MarkSF · 28-08-2013, 11:58

It's just that the suggestion that carburetor gumming is somehow due to ethanol is not correct I think, unless you have incompatible materials that are dissolving and then being deposited in the carb.

Deposits in gasoline have been a problem since the automobile was invented - just go to your local auto store and check out the range of gasoline additives, carburetor cleaners, FI cleaners, and so on to see what I mean.

I think if you had taken a look at the inside of the jets with a microscope, you would have found a different story.

**Tellie** · 28-08-2013, 12:10

A Vega ??? Whata piece of junk.
Now my Pinto, that was the best car I ever owned, right up until I traded it for a far better car, my beloved AMC Gremlin.

Cheechako · 28-08-2013, 12:20

Quote:

Originally Posted by Tellie

A Vega ??? Whata piece of junk.
Now my Pinto, that was the best car I ever owned, right up until I traded it for a far better car, my beloved AMC Gremlin.

I loved my Vega compared with my Pinto! but yeah....engine was short term! kinda let's you know that GM "testing" is BS doesnt it? My Pinto was a good car, but it was an early one with the British ford 1600 engine in it. My girl friend at the time had a later one with usa 2000 (?) engine... never did run good. The Vega just felt much more solid... GM really missed a big opportunity on that one, to make the first good small US car.... all they had to do was make the block cast iron like all their other cars....

Lake-Effect · 28-08-2013, 12:22

Quote:

Originally Posted by MarkSF

It's just that the suggestion that carburetor gumming is somehow due to ethanol is not correct I think, unless you have incompatible materials that are dissolving and then being deposited in the carb.

Understood.

My own particular preference for ethanol-free gas for small engines is mainly because it seems to remain "viable" for longer than gas with ethanol... and that alone justifies its use for me. Most common outboard problems are related to gas, so it seems sensible to have the best possible gas.

From looking at old gas, it seems that gas with ethanol breaks down and goes 'bad' sooner. Ethanol reportedly attacks fuel system components more than just gas. Is it possible that, since ethanol is more chemically aggressive but breaks down sooner means that it is more likely to leave insoluble deposits?

Just speculating. I don't know for fact that gas with ethanol leads to more gum formation.

For engine fuel-line problems, I do think this stuff is almost magic:

Can I have an 'Amen'?

Cheechako · 28-08-2013, 12:23

in a closed carbureator, gasoline doesnt evaporate that fast. Not sure why it would gum up if not evaporating. Started my little kicker in late june after being stored with gas in the carb since october. 2nd pull... no problem. Ditto for the riding mower and for the weed whacker.... an outboard shouldnt be hard starting from storing for a few weeks with gas in it.

Someone told me Union 76 stations have ethanol free gas....?

thomm225 · 28-08-2013, 12:39

Quote:

Originally Posted by Cheechako

I loved my Vega compared with my Pinto! but yeah....engine was short term! kinda let's you know that GM "testing" is BS doesnt it? My Pinto was a good car, but it was an early one with the British ford 1600 engine in it. My girl friend at the time had a later one with usa 2000 (?) engine... never did run good. The Vega just felt much more solid... GM really missed a big opportunity on that one, to make the first good small US car.... all they had to do was make the block cast iron like all their other cars....

I was going to point out earlier that even though some Pinto's were dying at 40,000 miles (2000cc engine) mine , a 1972 4 speed), which had the 1600cc engine lasted 80,000 miles plus before I traded it for another car.

And since I was 16-17 when I had it, I ran the living crap out of it. I never did know where that engine was built I just new that sawed off straight 6 looking engine was tough.

But the Pinto was still a POS car. I didn't know that until my sister's boyfriend let me drive his MG. I had never before driven anything near as good as that car. This was in 1973-74. And that thing was extemely quick. It had 2 or 3 carburetors also I believe and used only premium gas.

MarkSF · 28-08-2013, 12:45

I had a Ford Cortina 2000cc, which had the Pinto engine. The problem was that they tried to get away with one piston ring for compression AND oil control, instead of the normal 3 or 4.

At 70,000 miles it was a bit smoky. At 100,000 it was VERY smoky and at 101 it blew all the oil out of the filler and all over the engine bay, due to chronic compression failure.

To be fair, though, the engine was better than the rest of the car.