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

[SVMusic]

Originally Posted by SVMusic

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

Update, thanks again for the amazingly helpful advice. I swear we tried every single one of them! We don’t really know which one worked because the parameters seemed to change daily but the outcome was SUCCESS! Yippee! < jumping for joy>
But more importantly we learned SO MUCH from our sailing buddies.

[asistephen]

I had the same problem on my 2 stroke 5HP mariner outboard , first make sure the fuel cap is letting air through a simple enough task I just took the thing apart and blow the hole out. But the problem was in the fuel tap itself. I took it out of the bottom cowl engine housing , then undid the two small screws at the back of the tap and then this reviled a really small brass disc type filter ! It was full of black type sludge . So when the engine was demanding more petrol under load the fuel wasn’t getting through in enough quantitie this the engine would stall and then take about 10-15 pulls to start again. I simply blow the thing out put it back and problem solved. Try this and let us know how you get on . By the way my mate a marine mechanic said loads of other things possible as he’d just serviced it after I told him about this problem but I still ended up finding and fixing it myself.

[Souzag818]

Have NEVER had good experiences with Mercury OB's I've got one torn apart in my garage that I just walked away from. It's going to the scrap metal yard.... Now, a good old Johnson/Evinrude. Got 2 of those that start within 2-3 pulls every time. Ones a 1971, ones a 1986. They ain't pretty, but they're reliable

[Juggerknot]

All 2 stroke owners should have Berryman's dip, nothing cleans jets and carbs better. A gallon will last a regular consumer a lifetime...

[Juggerknot]

$300 to go through the carb and not diagnose and correct problem is not the hallmark of a "good" mechanic. Pull the carb and give it a 30 soak in Berryman's, problem solved or check off list and continue troubleshooting.

[curtis742]

I would suspect the fuel pump. It is a thin rubber diaphragm which is moved back and forth by pulsating pressure from the crankcase. These diaphragms are soft and very flexible. Alcohol in modern fuels react with the rubber causing it to become stiff and preventing the diaphragm from moving freely thus decreasing the fuel pumped into the carburetor. On all of our two stroke engines we use an additive called Seafoam in all our blended fuel/oil containers. Additionally there is usually a screen in the pump to keep contaminates out of the check valves in the pump. This screen is often overlooked during service and often is clogged. If the diaphragm is not soft and pliable or seems a bit stiff replace it.

[hellosailor]

Curtis-
You might want to take a look at the MSDS for Seafoam. It is about 1/3 each of naphtha (the base stock of gasoline), 1/3 isopropyl ALCOHOL, and 1/3 light machine oil. The naphtha is there as fuel, the alcohol is there to dissolve deposits, the oil is there because that much alcohol scours cylinder walls and they immediately need lubrication.

It is not miracle sauce. If you have engine components that are harmed by alcohol, it is also about the last thing you want to add to them. (And of course, you can mix up your own 10x cheaper.)

[curtis742]

My fire department was having a large number of chainsaw carb failures until we started using Seafoam. The carb diaphragms quit failing 6 years ago. When we are on a wildfire a chain saw that won't start is dangerous. We now use it in all of our two stroke engines as well as the pumps on the brush trucks. It doesn't matter what is in it, it works. BTW it also stabilizes fuel for some odd reason. My personal chainsaw is going on 7 years old and has never had a carburetor issue.

[a64pilot]

Originally Posted by Juggerknot

All 2 stroke owners should have Berryman's dip, nothing cleans jets and carbs better. A gallon will last a regular consumer a lifetime...

Be careful with that stuff, believe it or not but after a couple of years, it will eat thru the can.
Oh, and do NOT leave the carb in there overnight, some of them are made from zinc it seems and will literally be dust, takes hours though.

[Jeanneau 45.2]

Sometimes a sailor's procrastination gets rewarded. Tried the "easy" fix of spraying carb cleaner into the air inlet while running, but all I succeeded in doing was killing the engine (apparently carb cleaner is a lousy fuel). So I decided to "sleep on it" getting by using the choke. Voila, 2 weeks later, all is good!!! Wife said "wow, you fixed it!!". I just smiled and said "yes".

Originally Posted by Jeanneau 45.2

Very cosmic. I have a 2002 6HP Mercury 2 stroke which developed in the past week what appears to be a very similar problem. It starts on 1 pull and idles perfectly, but shortly after getting under way at speed, it also slows down to the point of "gasping for breath" (I know, I am putting a human symptom upon an inanimate object). I have drained all fuel from the carb, drained the 3 gallon fuel tank, and checked that I have fuel pressure at the hose / engine connection. I have not yet found the root cause, BUT I HAVE FOUND A GOOD WORKAROUND. PARTIALLY PULLING OUT THE CHOKE WHILE INCREASING THROTTLE TO CRUISING SPEED ALLOWS NORMAL PERFORMANCE. I have gone several miles multiple times without problems and my fuel consumption is in the normal range. This rules out, IMHO, spark and air issues, and must relate to a jet or other carb issue. One I get to a port where I can work on the outboard out of the water, I'll tinker. Suggestions welcome.

As an aside, how do you ensure that your dingy and outboard are never stolen in the Caribbean ... buy a Mercury Actually mine has been problem free until this recent malady.

[thruska]

Ditto Seafoam !!!

On the dingy theft protection...if an inflatable,
Deflate one side, keep a garbage bag filled with balloons in the dingy.
Drift....

[SVMusic]

Originally Posted by Jeanneau 45.2

Sometimes a sailor's procrastination gets rewarded. Tried the "easy" fix of spraying carb cleaner into the air inlet while running, but all I succeeded in doing was killing the engine (apparently carb cleaner is a lousy fuel). So I decided to "sleep on it" getting by using the choke. Voila, 2 weeks later, all is good!!! Wife said "wow, you fixed it!!". I just smiled and said "yes".

Love this so much! Hahaha

[SVMusic]

Originally Posted by Jeanneau 45.2

Very cosmic. I have a 2002 6HP Mercury 2 stroke which developed in the past week what appears to be a very similar problem. It starts on 1 pull and idles perfectly, but shortly after getting under way at speed, it also slows down to the point of "gasping for breath" (I know, I am putting a human symptom upon an inanimate object). I have drained all fuel from the carb, drained the 3 gallon fuel tank, and checked that I have fuel pressure at the hose / engine connection. I have not yet found the root cause, BUT I HAVE FOUND A GOOD WORKAROUND. PARTIALLY PULLING OUT THE CHOKE WHILE INCREASING THROTTLE TO CRUISING SPEED ALLOWS NORMAL PERFORMANCE. I have gone several miles multiple times without problems and my fuel consumption is in the normal range. This rules out, IMHO, spark and air issues, and must relate to a jet or other carb issue. One I get to a port where I can work on the outboard out of the water, I'll tinker. Suggestions welcome.

As an aside, how do you ensure that your dingy and outboard are never stolen in the Caribbean ... buy a Mercury Actually mine has been problem free until this recent malady.

This last quote about the mercury made the crabby captain laugh out loud! Awesome.

[hellosailor]

Carb cleaner is supposed to soften the hard varnish deposits and gummy deposits in the carburetor. So what happens when you try to use it as a fuel? Right, all that gummy sludge peels off the places where it has built up, and immediately tries to jam into the needle valve. Promptly clogging the engine.

This is why mechanics usually rev the hell out of an engine when they are pouring "stuff" into it and attempting to blow out deposits.

Whether they are pouring in yesterday's coffee to blow out carbon deposits (big magic, coffee is mainly water, water superheats as it flashes into steam, and that scours out engines) or using Seafoam (which is isopropyl alcohol to scour, naphtha fuel stock, and light machine oil to replace the oil they're scouring off the cylinder walls) there's no magic to it all. Just simple mechanical things and physics. There really IS logic behind it all.

[dkenny64]

SVMusic,
glad to hear you got it fixed..


we have a 2002 15hp 2stroke mercury..similar problems...


thanks for your post and questions..glad I didn't spend $300
on a carb clean and fix.. I wish your mechanic was more a mechanic

than a parts swapper..yes unfortunately there are lots of parts swappers
and few 'mechanics'.. I spent about 1.5hrs..to remove and clean and put back
the carb in our 15hp.. let's be fair..I've torn many engines and carbs to bits and put the back together..so this might be outside your skill set.. but I'll say this carb is as easy as they come...it was HARD to find instructions on how to tune it.WHY? not sure.. I spent more time find this info than removing the carb, cleaning and putting it back..


from what I've heard about traveling..keep the old beat up looking engine and crappy looking dinghy..theives don't want them..
-dkenny64d


so I'll keep crappy look Mercury( toss in the ocean) motor and my dinghy with 4 layers of patches on patches..