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

Aug 2, 2018
96
Beneteau Oceanis 40cc Little River, SC
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
 
Last edited:
Nov 6, 2006
9,884
Hunter 34 Mandeville Louisiana
Might want to have the coils and trigger checked.. sometimes, these will shut down under heavy load/higher heat conditions.. Water pump and passages.. some engines have a high temperature shutdown.. if it is a four stroke engine, low oil pressure can sometimes shut it down.. Mercury made both 2 stroke and 4 stroke motors that year..
 

danm1

.
Oct 5, 2013
164
Hunter 356 Mamaroneck, NY
Interesting that changing the fuel tank and hose worked for awhile. EPA compliant fuel tanks caused me no end of grief. If you have a hose with the pressure valve in it, the angle of the hose can cut off gas flow. There are newer models that don't require that hose and worked better for me.
 
Aug 1, 2011
3,972
Catalina 270 255 Wabamun. Welcome to the marina
If it bogs down, does it return to sortof normal if the throttle is closed?
 
Aug 2, 2018
96
Beneteau Oceanis 40cc Little River, SC
Might want to have the coils and trigger checked.. sometimes, these will shut down under heavy load/higher heat conditions.. Water pump and passages.. some engines have a high temperature shutdown.. if it is a four stroke engine, low oil pressure can sometimes shut it down.. Mercury made both 2 stroke and 4 stroke motors that year..
It is 2 stroke. Hubby perked up at your suggestion. Thanks!!
 
Aug 2, 2018
96
Beneteau Oceanis 40cc Little River, SC
Interesting that changing the fuel tank and hose worked for awhile. EPA compliant fuel tanks caused me no end of grief. If you have a hose with the pressure valve in it, the angle of the hose can cut off gas flow. There are newer models that don't require that hose and worked better for me.
We both feel the same about those epa compliant tanks. UGH!!
 
Aug 2, 2018
96
Beneteau Oceanis 40cc Little River, SC
If it bogs down, does it return to sortof normal if the throttle is closed?
Well, the answer to your question this morning would have been Yes, it returns to normal. But this afternoon, when throttling down, the motor shut off and left him stranded in the ICW! :banghead:
Now, it's too hot outside to try to fool with it. What do you suggest to either answer?
Thanks
Cara
 
Nov 30, 2015
1,337
Hunter 1978 H30 Cherubini, Treman Marina, Ithaca, NY
Hey there @SVMusic (Sunny and Crabby). Welcome to the forum. Saw your vinyl repair post. It motivated my Cindy to order material and reinstate the sewing machine to make a custom fit pedestal and table cover. She sews, I drink!

This issue, from my perspective and experience sounds like an air leak in the fuel lines, i.e. lack of fuel at fast throttle. Some ideas I can think to check would be primer bulb, fuel hose crimps, dip tube in fuel tank, carburetor transfer lines. This will be a dumb question...but is the tank vent open on the new tank? If you’ve been running E10 gasoline, you should probably rethink that. Ethanol can really degrade most modern plastic hoses used in the engine. This is a four stroke engine right?

OK, that’s all I got. Good luck...keep us posted. Tell Crabby to mellow and work the problem. This is a good place to contribute and get results.
 
  • Like
Likes: LloydB
Aug 1, 2011
3,972
Catalina 270 255 Wabamun. Welcome to the marina
Well, the answer to your question this morning would have been Yes, it returns to normal. But this afternoon, when throttling down, the motor shut off and left him stranded in the ICW! :banghead:
Now, it's too hot outside to try to fool with it. What do you suggest to either answer?
Thanks
Cara
It sounds like it’s starving. When it dies, does it buck and cough or just sort of sound like it’s running out if fuel, slowly fading away?
 
Sep 26, 2008
546
Hunter 340 0 Wickford, RI
Have you tried changing the fuel? I use Trufuel in my outboard. It comes available for 2 stroke or 4 Stroke engines.
It's pure fuel like we had back in the 60's and early 70's. No Ethanol. And really makes a difference.
 
Aug 2, 2018
96
Beneteau Oceanis 40cc Little River, SC
It sounds like it’s starving. When it dies, does it buck and cough or just sort of sound like it’s running out if fuel, slowly fading away?
Slowing fading away. (Like this sailor in the heat!)
 
Aug 2, 2018
96
Beneteau Oceanis 40cc Little River, SC
Could the choke be sticking?
hmm, we don't know how to check it, but it seems the flapper is closed even when it is sitting there. Not sure if it is supposed to be in that position.
 
Aug 2, 2018
96
Beneteau Oceanis 40cc Little River, SC
Have you tried changing the fuel? I use Trufuel in my outboard. It comes available for 2 stroke or 4 Stroke engines.
It's pure fuel like we had back in the 60's and early 70's. No Ethanol. And really makes a difference.
we use 93 octane no ethanol fuel. But that is great info. Never heard of Trufuel. good to know
 
Aug 2, 2018
96
Beneteau Oceanis 40cc Little River, SC
Hey there @SVMusic (Sunny and Crabby). Welcome to the forum. Saw your vinyl repair post. It motivated my Cindy to order material and reinstate the sewing machine to make a custom fit pedestal and table cover. She sews, I drink!

This issue, from my perspective and experience sounds like an air leak in the fuel lines, i.e. lack of fuel at fast throttle. Some ideas I can think to check would be primer bulb, fuel hose crimps, dip tube in fuel tank, carburetor transfer lines. This will be a dumb question...but is the tank vent open on the new tank? If you’ve been running E10 gasoline, you should probably rethink that. Ethanol can really degrade most modern plastic hoses used in the engine. This is a four stroke engine right?

OK, that’s all I got. Good luck...keep us posted. Tell Crabby to mellow and work the problem. This is a good place to contribute and get results.
The captain laughed OUT LOUD at your "she sews and i drink" thanks for making him smile!!
Vent tank is open, and running no ethanol gas.
It i a 2 stroke engine.
 
  • Like
Likes: BlowMeAway
Aug 1, 2011
3,972
Catalina 270 255 Wabamun. Welcome to the marina
It sure sounds like it’s starving. Could be air getting into the fuel flow, could be any of 100 things. Sorry for being so specific. Could be something slightly bigger than pita sized obstruction in a hose preventing fuel flow. Idles fine, but ask for huge fuel flow ( comparatively speaking ) and you don’t get it.
I’ll bet it runs just fine 5 minutes later.
 
Aug 2, 2018
96
Beneteau Oceanis 40cc Little River, SC
How do you know if the choke is functioning? How do you check to know if the ignition coils are functioning properly. We live on the boat and most of our mechanic tools are 4 states away.
 
Nov 30, 2015
1,337
Hunter 1978 H30 Cherubini, Treman Marina, Ithaca, NY
Please excuse my ignorance and this is not meant to be critical...but are you motoring a Bene 40CC with an outboard? Curious minds need to know. Coils should be checked for cracks in the polymeric encapsulant, as well as wire connection being loose. Extreme temperature swings can have a prolific impact on the plastic coating, as well as high humidity or rain ingress upon the coil. I still think this is a fuel flow issue.