Fuel pump?

Christie76

Recruit
Joined
Feb 12, 2015
Messages
2
I have a 40 horse Yamaha outboard. On the weekend went out on Saturday, it ran fine. But on Sunday took it out again, unloaded from trailer, started off good until I gave it gas. It acted like it was bogging down then dies. It would crank right up and idle fine until I try to go again and it dies. I checked fuel filter and it is clean. Just redid the carburetor a month ago because it was doing the opposite, wouldn't idle but ran if I gave it gas. It ran good after that was done. Now it is doing this. I'm thinking its the fuel pump? Any ideas?
 

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,585
Welcome aboard Christie76 :welcome: Great for you to join us on here...

If you suspect the fuel pump is your problem, remove the fuel inlet hose coming from the fuel pump to the carb(s) and crank it over to see if the pump is pumping correctly. If it is a mere trickle amount, then yes the pump is needing either replaced or rebuilt. When you experience this problem, is the primer bulb still firm? If so move to the pump. But if the pump is pumping a good amount then you still have carb issues...
 

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Drain carb float chamber onto a clean white rag to check for water or debris....carb Jets could be plugged again if there is any debris in fuel system....
 

Christie76

Recruit
Joined
Feb 12, 2015
Messages
2
I also forgot to mention that when me and my nephew was on the water trying to get it to run, he flipped the emergency fuel enrichment switch and it would stay running. But when we got closer to the dock he flipped it back to normal it would start dying again when I gave it gas. So now I'm thinking it has something to do with the Fuel enrichment switch?
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
depends on which way it is switched. There are 3 positions/
normal/automatic
open
and closed
If the motor will not run properly with red switch in normal position then you have a problem with the passages/jets in the carbs or possible to have hole in diaphragm in enrichment system maybe, but that would flood it
 

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,585
I agree with 99yam40 assessment. I was thinking the high speed jet being plugged. I know you stated that the carb(s) were just rebuilt, but any little piece of trash can plug a jet in a heartbeat. And if you find that it is a piece of trash in the main high speed jet, I would definitely change the fuel line as well. Could be the fuel interior liner is flaking off and that will plug a carb instantly. Using the fuel enrichment switch is merely covering the real issue from the carb. JMHO!
 

saltydog1

Seaman Apprentice
Joined
Oct 4, 2014
Messages
30
I had a similar issue with mine, it would idle fine but on take off would die, thought it was carbs although I had just rebuilt. Checked fuel pump like someone said earlier in the post and it pumped good fuel while turning it over but after further investigating I broke fuel pump down to inspect had a bad diaphragm bought a rebuild kit and that solved my problem.
 
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