# ongoing fuel issue but close to diagnose



## steve77777 (Nov 12, 2013)

Hello Ive had issues of my boat stalling while im going about 1,200 rpms for 10 minutes,but the boat is fine going 32 miles per hour for ever--I recently put a new bulb on and same thing happened ,then i bypassed everything with a seperate fuel tank and bulb and the same thing happened, the bulb goes soft and if i dont squeeze it 6 times it will stall but when i do squeeze it then it runs another 5 minutes while in slow idle at 1,200 rpms was what im doing it at, so what i think it comes down to is the fuel pump doesnt suck hard enough while running slow and is fine running at higher speeds, so if you guys think im right its either fuel pump or fuel pump diaphram how much does this cost to take it some where to fix and do you guys think this is my problem ,-- thx for feedback you guys really help out..


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## cutrunner (Jun 8, 2010)

What motor?
Does the boat have a built in tank or portable?
Could be an anti siphon valve if built in.
Also a cheap primer bulb (yes, even if its brand new)
Also if its a smaller motor you want to run a smaller line 5/16, and not 3/8
Also make sure the primer bulb arrow is pointing up at all times


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## steve77777 (Nov 12, 2013)

ok ill be more clear this time when i write, I take the boat out and while going at 1,200 rpms for 10 minutes the boat starts to die , i pump the ball and it saves it from dying and will run an additional 10 minutes.

So I got another fuel tank 3 gallon with a new primer bulb and hooked it straight to the engine and it started, ran great for ten minutes then started to stall so to save it i would pump the ball,if i dont touch the ball then the engine dies and the ball is soft and to start it back up i have to squeeze and prime the ball again..

I would also like to mention i can run 30 mph for over 20 minutes and there is not a problem

so I know its not the bulb,its not the anti syphon because i bypassed both of those, and the same thing happens, it must be the fuel pump or fuel diaphram on the engine itself...

can anyone tell me if im diagnosing this correctly?

Also its a 40 hp mercury 2 stroke 2003 engine

Thankyou everyone


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## DuckNut (Apr 3, 2009)

Not an expert but I think there are only two items that you did not bypass:

Fuel pump - may have a tear in the diaphragm.
Carb - maybe just needs a good cleaning.


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## steve77777 (Nov 12, 2013)

thankyou Ducknut, can i rule out carb if the boat runs really nice at all speeds if its receiving fuel and if the ball doesnt go soft?


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## cutrunner (Jun 8, 2010)

> Not an expert but I think there are only two items that you did not bypass:
> 
> Fuel pump - may have a tear in the diaphragm.
> Carb - maybe just needs a good cleaning.


This


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## cutrunner (Jun 8, 2010)

> thankyou Ducknut, can i rule out carb if the boat runs really nice at all speeds if its receiving fuel and if the ball doesnt go soft?


No because once at wot the idle circuit only makes up 10 to 15% of the power and the main makes up the rest
(Depending on your motor)
So sometimes a semi clogged idle circuit will do exactly what you are describing


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## cutrunner (Jun 8, 2010)

What primer ball is on it?
Is the ball pointed to the sky?
Have you bypassed all the quick connect fittings?


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## steve77777 (Nov 12, 2013)

i disconnected the line to the engine and put another line from a different ball and tank and it did the same thing...I just took it in to the shop,ill let you guys know what they find...


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## steve77777 (Nov 12, 2013)

ok they fixed it, it was the fuel pump diaphragm ,it wasnt seating very good so at low rpms it basically wasnt pumping, wow all that and finally done


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## DuckNut (Apr 3, 2009)

. [smiley=1-beer-german.gif]


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## TomFL (Oct 2, 2007)

Dangit I was just about to suggest the muffler to transmission adapter but glad you fixed it.

-T


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