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

[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

[Dave_S]

Has anyone checked the Fuel pump. ?

[Cheechako]

Tank vent is open?

[SVMusic]

Originally Posted by Dave_S

Has anyone checked the Fuel pump. ?

He said he doesn't know how. but i will look it up. Thanks!

[RickG]

Did the mechanic change the internal fuel filter? Do you have an external fuel fllter - check the o-ring.

I've had my share of frustration with our used Tohatsu 9.8 2-stroke. New outboards are expensive and have their own challenges. If the Mercury is a 2-stroke it is more than worth it to resolve the issues.

Cheers, RickG

[Jammer]

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.

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

Usually, problems with the motor failing abruptly after it warms up are ignition related. I am diagnosing one this weekend on my 1956 Johnson 3hp. Newer motors, with electronic ignition, are susceptible to the same.

[travellerw]

Here is the first thing I would do..

Take the dinghy for a ride at full throttle WHILE GENTLY PUMPING THE FUEL BULB. If that solves the problem then its defnately a fuel delivery issue. I would then change all the filters (even the hidden one under the cowel), then the fuel pump. Guessing it will be the fuel pump.

If pumping the fuel bulb does not solve the problem then its most likely an electrical issue (either the coil or CDI box).

[SVMusic]

Originally Posted by RickG

Did the mechanic change the internal fuel filter? Do you have an external fuel fllter - check the o-ring.

I've had my share of frustration with our used Tohatsu 9.8 2-stroke. New outboards are expensive and have their own challenges. If the Mercury is a 2-stroke it is more than worth it to resolve the issues.

Cheers, RickG

After the mechanic worked on the engine, and I got it back I checked the O-ring and fuel filter and the O-ring was severed so I purchased a new fuel filter with o-ring and replace both .
Makes us wonder about the integrity of the mechanic (as of most mechanics lol) so we don't want to bring it back to that same guy but he is the only one is our area.

[a64pilot]

If your going to cruise, your going to have to wean yourselves from mechanics.
Now is a better time than in the out Islands, here you have support if you have to have it, there you may not.

[scotty c-m]

Did that fix the problem?

[SVMusic]

Originally Posted by a64pilot

If your going to cruise, your going to have to wean yourselves from mechanics.
Now is a better time than in the out Islands, here you have support if you have to have it, there you may not.

You make a BRILLIANT point!

[SVMusic]

Originally Posted by scotty c-m

Did that fix the problem?

Hi Scotty, not sure which part you are referring to, but nothing has worked so far. We have on our list to check:
if the choke is functioning properly (but don't know how to check yet)
if its a coil and ignition problem (don't know how to check that yet either)
obstruction in carburetor

[Suijin]

Get one of these for 2003.

[leftbrainstuff]

You need 5 things to be right for any spark ignition to run properly. Remember the acronym FACTS. Fuel, air compression, timing and spark.

You've dealt with the obvious fuel items. Assuming that is not the issue.

From what you have described could you have an intermittent firimg issue. Maybe your spark or timing is impacted only under load. Tricky to diagnose apart from swapping out xomponents.

[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.