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View Full Version : 25 hp 4 stroke fuel starting problem



trentmc
01-08-2009, 03:55 PM
"I have a 25 horse 4 stroke that wont run right or start. It finnally started after disconnecting the fuel line after it burned some fuel off. After it finnally started I tryed to hook up the fuel line and as soon as I did it died. So I had to drain some fuel and disconnect the fuel line to start it again. After turning the motor for a little bit while triing to start it, fuel starts soaking out from behind the carb. Any suggestions?"

gary13
01-10-2009, 04:33 PM
I would probably suspect a stuck/sunk carb float

hjackson123
01-13-2009, 08:13 PM
"Trent,

Had the same problem. I was lucky that my fishing partner was a mechanic. It was a stuck float. Need to drain float bowl which sometimes works. I disassembeled the carb to see if there was trash causing the stick. No trash. The carb is easy to take off with socket. I keep tools for disassmbly with me at all times.

Herb"

islandboy
04-21-2009, 08:39 PM
"I've got the same problem with my F25 '03
no problems ever then now it will start and idle for 10-20 seconds then quit.
The pumper shaft at back of carb has a rubber boot which I discovered is cracked, if I manually pump it the engine starts and quits.
If I pump it 4-6 times gas leaks out of the cracked boot.
Question is of course what effect will the boot being cracked have? Will it let air in and prevent the engine from running once started?"

islandboy
05-23-2009, 07:59 PM
"Still having problems running my F25.
I replaced the rubber boot on the pump arm at top of carb, the one behind the throttle linkage and same result, if pumped it will start and die.
If pumped, started, and goosed to run at a higher rpm it will run at that higher rpm, but dies if returned to idle.
I've cleaned every orifice and jet i can find, but still no luck. bowl off, top plate off, solenoid thingy off and cleaned, fresh fuel etc.
It will start if that little arm is pumped with the linkage until fuel runs out of (?) and dies.
5-8 seconds.
Any help out there?"

islandboy
05-23-2009, 10:06 PM
"A second question/thought:
Anyone think the fuel pump would be at fault? Would it not pump at idle but pump at higher rpm? this engine will start and die, but start and run if I am able to advance the throttle and keep rpm at a 1/3rd plus."

rupertmja
05-23-2009, 11:16 PM
Maybe the float is stuck open and flooding your engine with petrol.
Bodge 1: Blow a bit of air into the carb drain plug to free it.
Bodge 2: Poke a pice of wire in the hole to try and free up the float.
Bodges - Might get you home but might happen again.
Better: Dismantle and rebuild the carb.

islandboy
05-24-2009, 09:07 AM
"Float is not stuck,
Carb has been cleaned out twice.
Will tackle fuel pump to rule out."

gary13
05-24-2009, 11:34 AM
""pumper shaft", I assume, is the accelerator pump. When you accelerate, it gives the engine a shot of fuel until it transitions to the high-speed system. The boot leaking could indicate the cup on the shaft is too worn to give the engine this shot of fuel. Continuously pumping it will flood engine on a lot of models. Gasoline squirting out of the boot on top is also indicative of a worn/cracked cup. The cup is either rubber or leather, and will disintegrate over time/use, allowing small particles to enter the jets/passages.
A bad fuel pump diaphragm will normally allow raw fuel to get in the crankcase and mix with the oil. It also makes the engine starve for fuel at higher rpm's. Pull the dipstick and see if you can smell any raw fuel in the oil.
If you can goose the throttle and get above the 'dead spot', I would suspect a blockage in the idle/low speed jet/passages first. They are small, and sometimes extremely difficult to clean. I would recommend you find someone with an ultrasonic cleaner to clean the carb(s). Liquid cleaners and air do not always solve the problem if there is somethng wedged in an orfice. Also, I would be wary about putting a carb back together with old parts, especially an accelerator pump or float seat/needle valve.
Hope this is of some help
Gary}"

silverwolf
05-24-2009, 10:25 PM
yamaha outboard: 9.9 hp 4 stroke. What does the electrical thing with the 2 wires on top of carb. do? I have cleaned the carb. put a new kit in it and a new fuel pump and it will start run a couple seconds then quit. If i squirt gas in the air horn it will remain idleing. Any Ideas
?

gary13
05-25-2009, 07:56 AM
"Lowell...I believe you are referring to the 'enrichment system' that replaces the old manual choke system. It enriches the idle mixture on a cold start engine until it warms up. To make it work, you turn the ignition switch to 'on' and depress the key....then start as usual.
I have noticed a lot here are rebuilding carbs. If you don't already have one, I would highly recommend installing a 10-micron water separating fuel filter. Do some research and find out all the headaches you can avoid with this one little addition."

islandboy
07-30-2009, 08:36 PM
"O.K. been away for awhile, am back to tackling the non running F25 MSHB
can anyone give guidance on the flywheel timing marks/alighnment and the corresponding mark lineup on the rear flywheel?
The belt seems a little loose and I'm wondering if it has slipped.
At this point, the fuel system checks out for float, wet plugs, no leaks ect."

islandboy
08-08-2009, 10:03 PM
"O.K. fixed the problem, timing O.K., fuel pump O.K. carb totally disassembled and 2 micro jets plugged.
Jets so small a single strand of speaker wire 18/2 is small enough to pass through.
Pumper cleaned, all passages, ran first crank.
We're fighting ethanol fuel, so it looks like run it dry each time.
Thanks all,"

gary13
08-08-2009, 10:40 PM
"Christopher
Glad you finally got that engine going. If you don't have one, I highly recommend a 10-micron fuel/water separator filter to prevent/lessen future problems. I use one that has the clear bowl on the bottom so you can see if any water is accumulating.
I have seen those jets plugged so bad they had to use a ultrasonic cleaner to get them cleared.
Good luck and happy boatinghttp://www.marineengine.com/discus/clipart/happy.gif<font color=""000000"">
Gary</font>"