Running an outboard dry after use

[billows]

On the instructions on my Mariner 4 stroke it recommends turning the fuel cock off and allowing the engine to run out of fuel to empty the carb bowl. Would it not be damaging to the fuel pump to be pumping fuel from a closed off fuel line on a regular basis?

[Xk59D]

Originally Posted by billows

On the instructions on my Mariner 4 stroke it recommends turning the fuel cock off and allowing the engine to run out of fuel to empty the carb bowl. Would it not be damaging to the fuel pump to be pumping fuel from a closed off fuel line on a regular basis?

Nope run it dry, I always have and no issues.

[mick]

I always run mine dry

[chriswood]

Me too - never a problem

[jeffstevens763@g]

dry its a diaphragm pump

[breezeblock]

religiously run them dry stale fuel is a pain in the backside I've seen so many engines in with fuel left in them from the previous year fresh fuel and a new plug away they go

[69cmw]

Never ran any outboard dry unless I was transporting it in the car and never had any issues with old fuel

[Maximus]

Originally Posted by 69cmw

Never ran any outboard dry unless I was transporting it in the car and never had any issues with old fuel

Same as...Had various carbed engines over the years

[Xk59D]

the point here is Mariner themselves say do it so if under warranty you best follow it.

either way, running it dry won't be an issue.

[spartacus]

Run my Tohatsu 2-stroke dry especially if it's going to be laid up for a couple of weeks. Doesn't do it any harm. If Mariner recommend it - then I'd do it.

[jonp]

I'm another who has never run any outboard dry (in 40 years of owning them) but if that's what the manufacturer states then maybe you should. Does it state a time period that it should be done for, example if you were heading out every day should it be drained or just if its not going to be not used for several months.

When I asked my outboard dealer this question he smiled at me and asked whether I drain the fuel from my car carbs or injection system.

Jon

[willk]

Originally Posted by jonp

When I asked my outboard dealer this question he smiled at me and asked whether I drain the fuel from my car carbs or injection system.

But then, you use your car every day? My overall experience of dealers - of cars, trucks, garden equipment, outboards and inboards, is that they NEVER adhere to the Manufacturer's recommended schedules. I suppose the manufacturer is pushing best practice ensuring an easy life for their kit and the dealers just want you gone?

In any case, FWIW, I generally empty the tanks of small petrol tools and shut off small outboard fuel supplies before running them dry - unless I know I'll be using them over the coming week. It works for me in several ways:
1. All fuel in play in the willshed is as fresh as possible - easy starting!
2. No engine will be left with two stroke and aging fuel drying in the carb/s
3. I own less petrol (I'm really mean )

[Poly]

Willk 3 only works for you IF you you time the shut off to stop when you would anyway otherwise you are burning fuel to empty the carb. Many years ago at a sailing club we used to have it down to a fine art so the engine stopped with enough momentum to carry the boat to the jetty. I've not run it dry since pretty mix two stroke days except when leaving the boat for more than a month or so.

[jeffstevens763@g]

to be honest i didn't run my 4 strokes dry until my aux had bad fuel my fault left it too long so i thought for the 90 if that happened too much of a faff to drain and why as i could run dry whilst washing down after rinse through. i also treat my fuel now too just in case i leave it too long.prevention better than cure i suppose.

[jonp]

Originally Posted by willk

But then, you use your car every day? My overall experience of dealers - of cars, trucks, garden equipment, outboards and inboards, is that they NEVER adhere to the Manufacturer's recommended schedules. I suppose the manufacturer is pushing best practice ensuring an easy life for their kit and the dealers just want you gone?

In any case, FWIW, I generally empty the tanks of small petrol tools and shut off small outboard fuel supplies before running them dry - unless I know I'll be using them over the coming week. It works for me in several ways:
1. All fuel in play in the willshed is as fresh as possible - easy starting!
2. No engine will be left with two stroke and aging fuel drying in the carb/s
3. I own less petrol (I'm really mean )

I own three vehicles, one is used daily while one is kept for bigger trips often left in the garage for many weeks without use. My boat tow vehicle is used only to tow the boat, none have had any stale fuel issues but I do get out on the water regularly.

The theory of stale fuel in the carbs or injection system is turned on its head when you consider the fuel sitting in the fuel line and filter, or do people drain this out and safely dispose of it?

I've got friends who only do a few trips per year and they certainly don't dispose of their fuel before trips. I have been told that unless the manufacturers state a higher octane fuel in any engine (outboard or car etc) then it shouldn't be used as this breaks down quicker.

With economic engines these days I seldom use more than 20% of my fuel in a day of boating, when you look at the age of some rigs that could mean there is fuel years old swilling around in tanks.

Jon

[Poly]

Originally Posted by jonp

The theory of stale fuel in the carbs or injection system is turned on its head when you consider the fuel sitting in the fuel line and filter, or do people drain this out and safely dispose of it?

to some extent I agree (and people do get concerned about fuel going stale in tanks). In a fuel filter or line there is nowhere for the volatile compounds to go. A carb however is not 100% sealed. Also because the passages inside a carb are so thin a tiny amount of waxy / varnish / gummy compound can make a big difference to the diameter screwing up the carb. The problem has been so widely reported (and it is not just boats but classic cars with carbs left for months/years too, lawnmowers etc), by owners, mechanics and manufacturers that I think it is a real issue. It was certainly much worse in pre-mix engines though.

I have been told that unless the manufacturers state a higher octane fuel in any engine (outboard or car etc) then it shouldn't be used as this breaks down quicker.

? I'd love to hear science behind that. I think they *might* mean that the compounds that make the higher octane fuels are volatile and thus readily lost from the tank? (I'm not even sure that is true but I've heard it said before) - of course that just leaves you with a slightly lower octane fuel - probably closely resembling the standard fuel. There is a load of misinformation around on "high" octane fuels which is confused by the US and EU using different definitions of octane, "normal" octane in many US states being lower than EU - so I've given up listening to most of it.

[C-NUMB]

I run it dry only for winter, and then plug in a fuel connector without a fuel line to avoid vacuum. Not that i know does it really mater but gives peace of mind. For the Mariner woud follow instructions. Does any of You run inboard engines dry during the season?

[HDAV]

I thought that higher octane fuels loose octane as they sit, so 6 month old high octane is no longer as high octane as it was when made. Running dry on a 4 stroke compared to a 2 stroke on premix is surely a different situation.

[Mextli]

On premix engines with more than one carb if you let them run dry you risk starving some cylinders of oil because fuel = oil.

I ruined my old Mercury 4 cyl 2 stroke that way.
Usually there's a drain screw on the carburettor bowl somewhere. My suzuki had a small pipe attached that led back to the fuel tank, so after a day of boating you just open the screws and let the carbs drain back into the fuel tank

Haven't been able to do so on my yamaha, though.

[gpsguru]

On all of the newer Mercury / Mariner EFi 4strokes, the manufacturer recommends just adding fuel stabilizer to the a full tank of fuel, then running on muffs for 5 minutes before any extended period of non use.

I have never run any engine dry ............... with the older 2 strokes the risk of heat damage from an oil starved weak mixture is a definite possibility.

I have never owned a carbed 4 stroke, but again, it would run lean once the fuel level drops below the float valve, and that cannot be good for any engine.

Modern fuels are much better quality than they were years ago .......... My cement mixer often stands for 18 months without use, yet always starts on the 2nd or 3rd pull ................. the lawnmower is rarely used from late Sept through to March, yet always starts up runs OK