Outboard Maintenance

[Matthew P]

I have a Tohatsu 6HP 4 stroke, 2009 that is generally reliable but often has slow running problems after being stored for the winter.  It starts first pull but will not settle down to slow running when warmed up and the choke is pushed in.

The mechanic who services it for me recently gave me some interesting insights. Apparently the fuel jet on modern 4 stroke outboard carburettors is very small diameter and easily blocked by gummy residue from stale fuel or, of course, rubbish in the petrol. This leads to fuel starvation when the choke is pushed in.  The jet hole is too small to rod through with even fine wire, so the mechanic has to remove it and clean it using an ultrasonic tank and filled with his magic secret fluid, not a task I would do myself.

Reasonably frequent use of the engine with fresh fuel keeps it clear.  But preventing fuel blockage over winter is difficult.  Draining the fuel at the end of a season may not clear old fuel from the jet, even if the carburettor is drained. So the best bet is drain the fuel at the end of the season, flush the cooling system through with fresh water etc but then get it serviced in the spring.

Any other ideas - excepting buy an old Seagull or row? 

Matthew
BR20 Gladys     

[Peter Taylor]

I'm still waiting (touch wood) to get a jet blockage on my similar Tohatsu. It never gets drained of fuel since in theory it is in use all year; however with a winter like the last one it can sit around for a couple of months or more. I do try to start it occasionally and I do get it serviced once a year.

One precaution I take is to buy fuel from the service station using a separate fuel container. I then pour the fuel into the remote fuel tank for the outboard through one of those funnels that lets fuel through but filters out water. I reckon if it holds back water it should hold back dirt! Also I buy the more expensive grade of fuel in the (probably mistaken) belief that it will contain less alcohol. My other assumption is that it is the alcohol in the fuel that is hygroscopic and attracts water.

Adding fuel conditioner is supposed to get over the "petrol going off" problem and also emulsify any water in the fuel.  However I find it hard to keep track of how much has/needs-to-be added, so last year I stopped adding the stuff.  Time will tell...

Peter

ps a sudden thought... if you were to stop the outboard by shutting off the fuel rather than via the kill cord button wouldn't that clear the jet of fuel? Anyone know?

[Graham W]

Matthew,

I have a Mariner 6hp, which I think is the same as yours but with a different badge. I need someone reliable and fairly local  to service it and your man sounds like he knows what he's doing. Can you recommend him?

[Matthew P]

Hi Graham, I'll message you details of the gentleman who services my Tohatsu.

Matthew

[Edwin Davies 2]

For up to date information on this problem check out vintage car websites, it also involves lawn mowers and generators.  My outboard did need the carb cleaning and so did my mower. I did this myself.  I now buy fuel in 5l lots and treat it in the container.  That  know all fuel is treated.

[Andy Dingle]

I've this same engine too..  Just with the Merc logo, but I'm assured by my mechanic it is exactly the same engine, imported by the same people, I just paid more... ! So far no problem thankfully. It's part of the warranty agreement to have it serviced so I've paid out for that this year .. Is that another con?

But I know my garden mower, which had last years left over outboard fuel in it just refused to run recently until I changed the fuel for new.
Can anyone please clarify what this petrol conditioning stuff is, what it does, is it worth it with a recommended brand?

Ta..

[Graham W]

Matthew's mechanic serviced my Mariner 6hp at the beginning of the season and thereafter it ran faultlessly, having previously suffered from quite bad carburettor problems.  I reckon that the answer to blocked jet misery is to get the service done by someone like him who has the knowledge, the ultrasonic equipment plus the secret ingredient.  To prevent evaporating fuel accumulating in unwelcome places and causing sticky varnish, I'm going to get the service done at the end of the season before the damage is done. 

I briefly entertained the idea of disassembling the carburettor myself but would probably wreck the engine.  There are all sorts of suggestions on t'interweb about various secret ingredients for cleaning the jets and other important bits, including boiling it in lemon juice mixed with distilled water.  Highly carcinogenic MEK (methyl ethyl ketone or butanone) was also mentioned.  This is a powerful solvent that was formerly used in the aerospace industry and can still be bought on eBay.  Apparently it works very well at eradicating varnish but the downside is liver tumours.

Another suggestion to avoid problems caused by ethanol and other additives in garage-bought petrol was to use aviation petrol (avgas) instead.  More expensive (approximately £1.60/litre) but allegedly more reliable.  That probably isn't too surprising as it is intended to help prevent Cessnas from falling out of the sky.  Has anyone tried this?

[Rob Johnstone]

This ontinuing thread has stirred a memory - when ah was a lad we had an elderly motor mower. After the winter break (us southerners had real winters in them days) it always started "first pull" provided one had remebered to turn on the petrol supply first. The rule was that you always stopped the engine by turning off the fuel supply and waiting for the thing to judder and wheeze to a halt. Dad said this stopped the carburettor from "gummimg up".

Perhaps we should adopt this practice with the outboard and regard the kill switch as "for use in emergency only".

[Peter Taylor]

Rob, I decided to start doing just that, but I found that the outboard motored on for ages using whatever fuel was left in the pipework. I've gone back to pulling the kill cord I'm afraid.
Peter

[Andy Dingle]

Rob/Peter.

I have been doing just this for many years now, and with lots of different motors. With the fuel additive I use and religiously running the carb dry ..  so far..  touch wood.. spit on the mat and call the cat a b'stard, (look it up, before the outraged PC brigade berate me!), all has been well.
I agree it takes ages to run dry, I just leave it on tick over whilst sorting the boat out. Usually she coughs and dies in time enough to enjoy a sundowner in the cockpit..

I've got a nice pic of just such an occasion when I found the outboard well completely full of little wriggly writhing elvers.. must of been many thousands of 'em who didn't seem too bothered with the engine ticking over! Unfortunately I can't seem to transfer it off my phone at the mo ..  I'll try again later when I've got more time...

(Can you eat elvers?!)

[Graham W]

Can you eat elvers?

They weren't available to buy (officially) for many years because they had been fished out on the Severn but are back in some fishmongers again.

They should be scalded in hot water first - that kills them, then bacon should be fried in a pan and removed. Fry the elvers for about a minute in the bacon fat before breaking a raw egg in to them.  The result tastes like fishy spaghetti. The Spanish fry them in olive oil with garlic and chilis.

[david]

Check  out the  associated  sites below the photo for more ways to cook them than I knew  existed.
https://www.google.com/search?sclient=tablet-gws&site=&source=hp&q=elvers&oq=elvers&gs_l=tablet-gws.1.1.0l3.3323.6022.0.7991.7.7.0.0.0.0.389.1769.0j2j2j3.7.0....0...1c.1.64.tablet-gws..0.6.1466.0..0i131k1.kyhNP0XFBY8#imgrc=rFJhWgHlnMNRLM%3A

⛵

[Graham W]

A possible way to avoid constant fettling with blocked outboard carburettors - see http://www.swallowyachtsassociation.org/smf/index.php/topic,1377.msg10207.html#msg10207

[SteveWD]

It can be a long time between turning off the fuel and waiting for an idling engine to use up the fuel in the carb and stop. If you are alongside and securely moored up, put the engine into gear and use more throttle: the more throttle you use, the less time it takes. The boat will also be held steadier while you tidy up.

[Graham W]

So, I collected my newly-serviced Mariner 6hp from the mechanic today.  He mentioned that when he was stripping down the business end, there was black-coloured fuel left in some of the pipes and carburettor.  This must have been the remains of Greek petrol from last summer, well on its way to depositing varnish throughout the carburettor and ready to cause problems for next season.

I had given him a small bottle of Aspen 4 alkylate petrol to tune the engine to.  He hadn't heard of it before and looked it up on t'interweb. He noted that it was much more expensive than garage-bought petrol (true) but was impressed with how unsmelly the exhaust fumes were.  Given how little fuel I use in a year, and how irritating, not to mention unsafe it can be to suffer from blocked carburettor misery, I think the high price per litre (£3.70) is worth paying.  And no need to waste fuel by running the carburettor dry - Aspen claim that their fuel will last up to five years without degrading.