put outboard in gear in a test tank?

[vildric]

Hi!

I have a little 3.5 outboard.

I forgot last time (and first time) I used it to run it with the fuel valve close to "run dry" the carb.

So I tried to do it at idle on the neutral in a test tank, but after like 5 minutes of idling with the fuel valve closed, it never stalled.

Can I put it in gear and run it in the test tank to consumn more fuel to see if it will stall?

Because 5 minutes without stalling with the fuel valve off, I begin to suspect a bad fuel valve...

 

[gordmac]

You can but it churns the water up a lot which can be a problem in a small tank. The valve can be checked by disconnecting the fuel pipe after the valve and seeing if the fuel flows with the valve shut.

 

[BruceK]

Is it a 2 stroke or 4 stroke? Because if it is a 2 stroke you really dont want to be running it dry. In fact the whole concept of running the carbs of any engine dry is AFAIC based purely on superstition, mumbo jumbo and "my mate told me so it must be alright" i.e. pure bollox. If you are going to let the engine stand for extended periods use fuel stabilizer. Carbs do not like being stored dry I assure you. Causes rubber and plastic components to dry out, warp, crack and perish. If you have a drain plug in the carb bowl use that to flush out any trapped water and debris

 

[Fantasie 19]

In fact the whole concept of running the carbs of any engine dry is AFAIC based purely on superstition, mumbo jumbo and "my mate told me so it must be alright" i.e. pure bollox.

You're the only person I've ever seen on here who has said that... you may be an expert, I have no idea, but the body of opinion would disagree with you...

 

[SAMYL]

Almost impossible to run a carb dry. The engine will run until the float bowl level drops below the normal level but it will not run 'dry'.
Do as Bruce suggests above.

 

[BruceK]

You're the only person I've ever seen on here who has said that... you may be an expert, I have no idea, but the body of opinion would disagree with you...

Well there you go. The body of opinion. Love that term, never read the manual but has an opinion. As stated above by SAMYL you cant run a float bowl dry. So next comes the old adage, I run it "dry" so it doesn't gum, varnish, shellack etc etc take the flavour on the month and stick by it. Running it "dry" hastens the process. Then of course as mentioned the rubber diaphragms (fuel pump), floats etc aren't designed to dry out. Plastic fittitings will shrink, floats will change density, needle and seat loose their seal etc etc. It's not rocket science mate. Carbs were designed specifically to remain wet all their lives.
Of course that is not to say fuel wont go all grubby in the float bowl if left for a long time, just that running it "dry" is a lesson in futility and ignorance. Use fuel stabiliser :encouragement:

 

[Fantasie 19]

Oh I don't disagree... I'm a mechanical numpty, but your comments certainly make sense....

What do you recommend (fuel stabiliser)... secondary question - is it better to use Super or Normal Unleaded (mine's a 4 stroke) in your view???

 

[BruceK]

I use Quicksilver, but don't really have an opinion on that, it's just readily available at the Chandlery. I also never store the little OB without running it to temp once a month. It's 1985 vintage and still runs a treat and never broken down.
For a 4 stroke what does the manufacturer recommend? What is the compression ratio and does it suffer from knock / pinking? Most recommend an octane rating of 89 or higher rating with 87 being the minimum.

 

[Fantasie 19]

Most recommend an octane rating of 89 or higher rating with 87 being the minimum.

Was thinking more about ethanol content and the like than performance... the engine runs fine on normal, I've always used it, but never to old to change....

 

[BruceK]

In the UK ethanol content hasn't reached the proportions where it really becomes a problem tbh. The biggest bugbear with ethanol content is leaving water in the fuel bowl causing corrosion and salts to form. Draining the fuel bowl via the drain plug /screw periodically is just good practise which is different from running "dry"

 

[Fantasie 19]

Thanks - interesting stuff to think on...

 

[Tam Lin]

If you put your outboard in gear in a tank, make sure that you have clamped it on securely! How do I know? Let's just say that I was surprised how long it ran for underwater!

 

[jac]

Why not just remove the prop and run it in the tank. It should minimise the amount of water displaced.

 

[rbcoomer]

If you put your outboard in gear in a tank, make sure that you have clamped it on securely! How do I know? Let's just say that I was surprised how long it ran for underwater!

Wow! Big tank...

I can only do idle in gear and even then need the hose running to keep the tank topped up - 90hp empts a water butt quite quickly if you blip the throttle - don't ask me how I found out!

 

[jfm]

Why not just remove the prop and run it in the tank. It should minimise the amount of water displaced.

He is trying to get the engine to do work and burn fuel faster

 

[jac]

He is trying to get the engine to do work and burn fuel faster

True but putting some revs on with no prop must surely use more fuel than idle with a prop as the engine is working a bit more - just not as much as it would with a prop.

I know when I rev 2t tohatsu 2.5 with no prop it seems to empty the carb pretty quickly but have never timed it.

 

[jfm]

True but putting some revs on with no prop must surely use more fuel than idle with a prop as the engine is working a bit more - just not as much as it would with a prop.

I know when I rev 2t tohatsu 2.5 with no prop it seems to empty the carb pretty quickly but have never timed it.

Sorry if being thick but I'm not seeing the benefit of getting spanner out and removing the prop. If your idea is to rev it to burn fuel faster, you can rev it in neutral; I'm missing your point in removing the prop

 

[tico]

Brings to mind memories of 'happy1' testing his bilge pump!