Outboard woes

[oldbloke]

All good advice. It's bound to be a fuel problem. I have become a bit of an obsessive about petrol. Always buy from a busy petrol station, not the fuel barge, use a funnel with a filter, empty, not just run dry, the carb. If only using a couple of gallons a year then use the horribly expensive alcohol free petrol.
, and certainly use this for the last run through of the year.

 

[ash2020]

First things first:

• Did you open the tank vent and, if applicable, the fuel cock?
• If you’re using an external tank, check that the fuel hose isn’t pinched anywhere.
• It really sounds like fuel starvation, so confirm the fuel is flowing freely.

Next steps:

• Inspect the fuel filter and replace it if clogged.
• If the engine still stalls, open up the carburetor and clean the jets and passages thoroughly—varnish or debris can easily cause this issue.
• Check the fuel pump diaphragm for wear or cracks; a weak pump can’t keep up under load.
• Verify the spark plugs are clean and properly gapped.
• Look at the air intake for obstructions and ensure the choke isn’t sticking.
• Finally, consider the age of the fuel—old or stale fuel can cause poor combustion. If it’s more than a couple of months old, drain and refill with fresh fuel.

Thank you. There isn't a tank vent on the external tank, but I did try opening the filler cap a bit. I don't usually run it with the cap open.
The strange thing is that it runs well in neutral but stalls under load.
I will have to clean the carb thoroughly but I don't think I can get the motor into the dinghy and ashore and then back again. Lifting it was what did my back injury in the first place. 26 kg.
I never keep old fuel so I don't think that's a potential issue.

 

[ash2020]

All good advice above. I'd suggest that you ensure that the prop's clear, and does rotate freely.
I've got to ask though, do you drain the carb at the end of each day that the engine's used? Annoyingly, this does require removing the motor cover, and unscrewing the drain screw on the side of the carb, but is a big factor in many of the 'motor's not running right' scenarios, as the fuel's 'gone off' in the carb and causes problems.
Best of luck.

Thanks Jamie. I don't drain the carb as the screw is very difficult to get to and I'm bound to eventually drop it into the briney. It would probably be good to disconnect the supply pipe and run it dry.

 

[ash2020]

Yes, I always do that, but specifically with these engines there's a significant amount of fuel that remains in the carb bowl, even after the engine has 'died'. Also, on these engines it's pretty much impossible to remove the carb bowl without removing the carb from the engine.
I hope this manual is some use.

The odd thing was that it started and ran well from the mooring to the pontoon, which would have used more than a bowl full of fuel. It's only when we left the pontoon and travelled some distance that it started to play up. Thanks for the manual BTW. It's a Tohatsu so I don't know if the Mercury and Mariner are similar. Actually, I've just found the Tohatsu service manual online.

 

[ash2020]

I went from inboard diesel to outboard petrol and had pretty much the same problem. Eventually tracked my woes down to that orrible E10 fuel which I think is 95% the primary problem with them. Changed to 99 octane plus an additive and for the last 12 mths its run very well indeed.

That's interesting. Trouble is, it's nearly impossible to get E5 fuel near here. The nearest petrol station is a half hour drive and they certainly don't have it. BTW, what additive do you use?

 

[Refueler]

I read the replies and I wonder if they really read the OP's into ?

Guy says the engine starts and revs fine in neutral.

Put into gear and it stalls.

That to me says - fouled prop or shaft ... possibly picked up fishing line or something after leaving pontoon ...

Before dipping into changing plugs / fuel and other such ... lift the engine .. check that prop is free and not fouled ... good idea to actually remove the prop and check the shaft - make sure nothing wrapped around it ....

 

[ash2020]

I read the replies and I wonder if they really read the OP's into ?

Guy says the engine starts and revs fine in neutral.

Put into gear and it stalls.

That to me says - fouled prop or shaft ... possibly picked up fishing line or something after leaving pontoon ...

Before dipping into changing plugs / fuel and other such ... lift the engine .. check that prop is free and not fouled ... good idea to actually remove the prop and check the shaft - make sure nothing wrapped around it ....

Thank you for being possibly the only one to spot that. It's not just a fuel or spark plug issue.

 

[thinwater]

Thank you. Yes, I do have the anchor at the ready but it was in the main channel which was probably a bit deep, but yes, always a possibility.
I will get the motor home and strip the carb. I would do it in the winter anyway, but unfortunately, it needs the motor to get to the lift out yard on the 28th.
Unlikely to be the hose and fittings as they are in good condition and relatively new.
I will look into additives but I'm not generally in favour. I'd rather keep the fuel fresh and used or replaced regularly.

The fitting that plugs into the motor does not last long. No, I do not think it is the problem this time, but just keep in mind that a few years is sometimes all you get. The flexing when you tilt the motor is hard on them. I carry a spare after being burned several times. A few small jubilee clips are also good to keep on the boat.

 

[ash2020]

The fitting that plugs into the motor does not last long. No, I do not think it is the problem this time, but just keep in mind that a few years is sometimes all you get. The flexing when you tilt the motor is hard on them. I carry a spare after being burned several times. A few small jubilee clips are also good to keep on the boat.

Thanks. Good suggestions.

 

[lustyd]

Surely its easier just to turn the fuel off and run it dry ?

We’ve found with modern fuel on a 4 stroke that can lead to the carb corroding as the ethanol in the fuel brings water in and you’re adding air. The corrosion then blocks the jets.
E5 fuel improves this, as does leaving fuel in the carb and just stopping it manually.

 

[jamie N]

Thanks Jamie. I don't drain the carb as the screw is very difficult to get to and I'm bound to eventually drop it into the briney. It would probably be good to disconnect the supply pipe and run it dry.

Amongst all of the other advice, the screw doesn't need to be removed as the carb bowl begins to drain fully after a turn or so of the screw, and did surprise me with how much fuel had been left in there after 'running the crab dry'.
I'm glad you found the Tohatsu manual, and you're quite right to see that the Mercury/Mariner brands are simply rebadged Tohatsu items.

 

[winch2]

That's interesting. Trouble is, it's nearly impossible to get E5 fuel near here. The nearest petrol station is a half hour drive and they certainly don't have it. BTW, what additive do you use?

From what I understand the Ethanol rich E10 absorbs moisture making it less combustable. Then add to that the permanently damp environment at sea and you can see the problem. I've got various additive bottles in a locker, no idea what they are but they all do the same job. I've also noticed that Shell and Harvest stations that are near water seem to have the E5, tho probably just a coincidence.

 

[Egret]

E5 fuel improves this, as does leaving fuel in the carb and just stopping it manually.

So with E5 petrol and Mercury or Honda additive, is it better therefore now to not to unplug the fuel and let it run until it stops bot to simply stop it with the stop button - using outboard every couple of weeks or so?

 

[winch2]

Put into gear and it stalls

I totally agree with ur thinking re a fouled prop but with regard to the fuel, E10 is not really old fashioned petrol but some weird concoction and from my non scientific investigations if it gets a whiff of H20 will fail. I had no end of mishaps running E10. Opening the throttle it would just die, wouldn't start, mis-firing etc.

 

[Refueler]

We’ve found with modern fuel on a 4 stroke that can lead to the carb corroding as the ethanol in the fuel brings water in and you’re adding air. The corrosion then blocks the jets.
E5 fuel improves this, as does leaving fuel in the carb and just stopping it manually.

I always stop the engine by turning off the fuel if its going to be stopped for more than a few hours.

Most carbs I see are alloy ... so where's the corrosion ?

The blockage of jets is usually GUM formation ... from fuel left in the carb.

 

[Refueler]

I totally agree with ur thinking re a fouled prop but with regard to the fuel, E10 is not really old fashioned petrol but some weird concoction and from my non scientific investigations if it gets a whiff of H20 will fail. I had no end of mishaps running E10. Opening the throttle it would just die, wouldn't start, mis-firing etc.

I'll just mention that Fuel is my business ... I am fully aware of the blends of fuel ...

I run E10 (95) in all my outboards .. main engines ... cars .... garden equipment ... with very little problem, I agree that I may have to pull the 'cord' a couple of times more compared to 'original' gasoline ... but that's all. I do not use additives in gasoline ... I certainly do not waste my money on Aspen ... an Alkylate concoction... to use your word.

Fouled prop ... here's an example that should not happen but does ........

6 cylinder VP AQ170 driving a 280 outdrive leg on my Primor 24. If I get off line in my channel and prop gets in the soft mud / weed bottom ... it often stalls the engine ... To get out of that - I may have to keep restarting engine 3 or 4 times as it stalls each time put into gear .. luckily the moment it goes into gear is usually enough to give a little thrust to move her. Once out of the crud - she fires up and runs normal.

 

[lustyd]

So with E5 petrol and Mercury or Honda additive, is it better therefore now to not to unplug the fuel and let it run until it stops bot to simply stop it with the stop button - using outboard every couple of weeks or so?

Yes, draining the carb is old advice from 2 stroke days to avoid oil gumming things up. You don’t have oil in the fuel so ignore that advice as it leads to corrosion.
The drain plug on my Yamaha doesn’t even lead to a hole, you’d have to drill it out yourself.

Do check the fuel system is clean, and ensure the fuel cap isn’t rusting inside the tank.

 

[lustyd]

Most carbs I see are alloy ... so where's the corrosion ?

On the alloy. Obviously. All metals rust, not all of that rust is rust coloured.
E10 contains ethanol which can attract and retain moisture. Draining the carb just adds air to the mix and causes the bowl to corrode, making a dust that blocks the carb.

 

[Refueler]

On the alloy. Obviously. All metals rust, not all of that rust is rust coloured.
E10 contains ethanol which can attract and retain moisture. Draining the carb just adds air to the mix and causes the bowl to corrode, making a dust that blocks the carb.

Well after decades of doing what I do .. that I have never seen in any of the many engines I have. I am well aware of properties on Ethanol.

To do what you claim - would take years .... and anyway - the engine and carb would be used at times - removing what ever miniscule amount was ever formed ! Moisture would be drawn from the air in the bowl .... which actually is always there even when running as the bowl is never 100% full .. the carb shuts off well before then ....

Sorry but not convinced at all. Theoretical bunkum !!

 

[lustyd]

Theoretical bunkum !!

Direct experience, actually. Some of us like to own our engines for years.