Help us before my husband throws our Mercury outboard in the water!

[Allatsea]

Hi all,
I can sympathise SVMusic, you have a set of symptoms very similar to my brothers 3hp Mercury, which many experts and others could not resolve - until a knowledgeable mechanic pointed out the plastic fuel cap was being attacked by the fuel (not sure if it contained ethanol).

The type of plastic used for the fuel cap was incompatible with gasoline - a problem apparently known by Mercury, but not widely known by Mercury service personnel here in Australia.
The result of this incompatibility was fine black specs of plastic inhibiting the flow of fuel through the fuel filter and carburettor jets etc.
So, a strip down and clean of the entire fuel system resolved the problem...until the next time.
Despite the numerous times my brother paid the Mercury mechanics to ‘service’ the outboard, none of them identified the actual cause of the problem.
Naturally, they insisted these procedures were not covered by warranty, so he had to pay each time the ‘serviced’ the outboard.
Hope this helps....

[joefults]

Throw it overboard and buy a Japanese brand outboard!

[a64pilot]

Originally Posted by joefults

Throw it overboard and buy a Japanese brand outboard!

It’s Tohatsu, is that Japanese enough?
I doubt many if any smaller outboards are built in Japan, my Suzuki is made in Singapore I think.

[travellerw]

Originally Posted by joefults

Throw it overboard and buy a Japanese brand outboard!

Sigh... I vote this as the most ignorant post response this year!

[model 10]

I think my Yamaha Enduro was made in Japan.

[SpiritBear]

Originally Posted by er9

i used to ride dirt bikes and we would sometimes have a similar problem if a carburator jet was clogged, gummed up with fuel tarnish or undersized. i went through all the same things you did once and finally ended up replacing the jet that controlled the low end throttle (opposite problem your having) with a slightly larger jet and the bike ran better than it did with the factory supplied one. a lot of mechanics will soak a carburator in solvent as part of the re-build process but this is not enough to clean the almost microscopic hole in the jet. i dont know your motor but it might be worth finding out how many and where they are and replace them one by one if all else fails.

I concur with this suggestion. If the motor is bogging down under load and seems to start to run OK again if you back off the throttle it is almost certainly a fuel supply or fuel mixture issue. Clogged main jets are often the culprit. The other culprit is often a badly set bowl float that doesn’t leave enough reserve in the bowl. Investigate the full fuel supply from tank to carb, including any tank venting blockages. i do not recommend simply trusting the experienced mechanic to have done a complete job because they sometimes get it wrong.

If the motor plain cuts out (not stumbles, but quits entirely) under high load and doesn’t recover right away I would recommend replacing the coil pack, spark plug wire and plug. I am older engine this might not be a bad idea in general.

I’m also in the “have owned many motorcycles” camp. The essence of any 4-stroke engine is “Suck, Squeeze, Bang, Blow”. A two stroke is “Suck/blow, squeeze/bang”. One just has to ensure that you got gas and spark in the right amounts and at the right time.

[Ericson38]

I have the 1st half of the Official 15 Merc 2 stroke shop manual as a PDF (about 2.5 Meg) but don't know how to post it here. This section deals with carbs, ignition and the like. Our 1997 year model 15 merc on a 310 AVON will spank a 2 stroke Yamaha on the same boat.

[jabrockert]

I had the same problem with a 6HP Mercury(toshiba). 4 different shops/ mechanics over 5 years, nothing every made it better. Did everything list in this thread several times.
Decided one more try with a mechanic in Corpus Christi. Carried the gas/fuel line and outboard 6HP into a shop, ask for someone to look at it. Mechanic Gary listened, said it would probably take him a little time, he popped the cover off, looked at the carb and said "behind this little brass plug is an air/mixture screw that is probably plugged and since the brass plug is still there and it looks like no one has bothered to take it off, I'm going to take the plug out and see". So he drilled out the brass plug, popped it off with a screw then cleaned the air/mixture screw and the engine has run like new every since.
Question is: Why did 4 different shops/mechanics on the texas gulf coast Never know about the hidden air/mixture screw, and why didn't the manual tell me about it? : Answer: engine was approved for California and your not allow to adjust it.

Lesson learned

[Clipper747]

If your Mercury is a two stroke I have ripped two strokes apart. I have found many a problems to be dirty carb, filters and spark plugs. I read your responses, have you cleaned your gas can and bulb? Two strokes are very sensitive to the oil used and dirty gas. My two strokes only likes an injector oil, go figure. IF it's a two stroke they are much easier than a four stroke. My two stroke would cut out and it was multiple problems, connections that were loose (needed re-sodering), dirty filters and carb, and gas lines. If you are handy take it apart and check your connections. If you are near Orlando give us a shout, we might be able to help. I also agree with the air/mixture plug, we adjust this quit often. This is an easy check! Jane

[Nightcrawler]

I admit, I haven't read every entry on this post, so apologies if this has come up. You need fuel, air and spark. Seems like the air issue hasn't been mentioned. I've had spider nests and once even a chipmunk food stash lodged in the air inlet. These happened on a mower stored over the winter and on an old Gale outboard. Even got my Fx4 jammed up when a critter tore all the insulation around the A/C bonnet and stuffed it in the air cleaner. You might check the air intake channel and be sure it's clear. The motor will idle fine, but can't pass enough air to run under load.
Good luck!

[Roy Blue]

I hope this helps, you have to split the engine. By the propeller at the bottom is a rubber impeller in the water pump. This breaks down in time and the bits break off. They get sucked up and pushed up the cooling system and get stuck. At first the water is cold but as the engine overheats it ceases. Take it all apart make sure the system is clean and then replace the impeller. Be careful here because if you replace it the wrong way you will have to start again with a new impeller. Now when you started originally did the peehole really push the water out but then slow down. A sign it was blocking. It should flush out quickly all the time the engine is running. regards Roy

[j.g.evans]

I had the same problem on my Mercury 15. The cure was to replace the needle valve in the carburetor with an all metal version. The standard needle valve has a rubber tip and I think it gets stuck closed and the motor runs out of fuel.

[windrider9999]

Change coil. Dhould do it.

UOTE=SVMusic;2692652]We have a 2003 Mercury 15hp outboard motor on our dinghy (which we purchased with our Beneteau sailboat) and it shuts down (or off) when under a heavy load.
He had a mechanic rebuild/service the carburetor ($300) and still have the same problem.
Since then he has tried:
-Changing the fuel tank and hoses (helped it to work for a while and then went back to the same problem)
-Changed the fuel in the tank
-Changed the gaskets and fuel filter
-Changed the spark plugs.
He removed the cowl and ran the motor with no load, it was fine but when he engaged the transmission to full throttle, it bogs down.

Does anyone have any helpful suggestions so that he doesn't end up throwing it in the canal? My sunny side can only get us so far!
Please send help! (Or a new motor if you have one!)
Thanks
Cara[/QUOTE]

[jimisbell]

Originally Posted by jabrockert

I had the same problem with a 6HP Mercury(toshiba). 4 different shops/ mechanics over 5 years, nothing every made it better. Did everything list in this thread several times.
Decided one more try with a mechanic in Corpus Christi. Carried the gas/fuel line and outboard 6HP into a shop, ask for someone to look at it. Mechanic Gary listened, said it would probably take him a little time, he popped the cover off, looked at the carb and said "behind this little brass plug is an air/mixture screw that is probably plugged and since the brass plug is still there and it looks like no one has bothered to take it off, I'm going to take the plug out and see". So he drilled out the brass plug, popped it off with a screw then cleaned the air/mixture screw and the engine has run like new every since.
Question is: Why did 4 different shops/mechanics on the texas gulf coast Never know about the hidden air/mixture screw, and why didn't the manual tell me about it? : Answer: engine was approved for California and your not allow to adjust it.

Lesson learned

I am in Ingleside on the Bay, where in Corpus did you take the motor. I need to have a good shop on my list.

[Colin A]

Originally Posted by jabrockert

I had the same problem with a 6HP Mercury(toshiba). 4 different shops/ mechanics over 5 years, nothing every made it better. Did everything list in this thread several times.
Decided one more try with a mechanic in Corpus Christi. Carried the gas/fuel line and outboard 6HP into a shop, ask for someone to look at it. Mechanic Gary listened, said it would probably take him a little time, he popped the cover off, looked at the carb and said "behind this little brass plug is an air/mixture screw that is probably plugged and since the brass plug is still there and it looks like no one has bothered to take it off, I'm going to take the plug out and see". So he drilled out the brass plug, popped it off with a screw then cleaned the air/mixture screw and the engine has run like new every since.
Question is: Why did 4 different shops/mechanics on the texas gulf coast Never know about the hidden air/mixture screw, and why didn't the manual tell me about it? : Answer: engine was approved for California and your not allow to adjust it.

Lesson learned

The plug was put in for EPA to prevent tampering to the fuel mixture which was required to meet emission specs. Some mechanics won't touch them and just dip the carbs. In my experience to really clean them the plug needs to be taken out and the screw returned to it's original position.