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Charles
Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3343
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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I have 2002 25hp murcury,put kit in carb and new diapham and

Customer Question

I have 2002 25hp murcury,put kit in carb and new diapham and the only way it will stay running after start is pump the bulb
JA: Sometimes boat issues seem like they'll be really complicated, but end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.
Customer: I put a kit in carb and replaced diapham,fuel lines and tried different tank and the only way it will run after you start it is pump the bulb
JA: Is there anything else important you think the Marine Mechanic should know?
Customer: Naw
Submitted: 3 months ago.
Category: Boat
Expert:  Charles replied 3 months ago.

Hello, my name is***** will assist you.

Expert:  Charles replied 3 months ago.

Would you please post the serial number of the engine?

Customer: replied 3 months ago.
Ot497861
Customer: replied 3 months ago.
Could it be an entinal vacuum problem?
Expert:  Charles replied 3 months ago.

I think that the problem will be on the engine. You eliminated the gas tank when you tried another one.

When you had the carb off, did you also replace the base gasket?

Customer: replied 3 months ago.
No I didn't but did spray carb cleaner around it didn't make any difference on the way motor ran
Expert:  Charles replied 3 months ago.

Was the spring still attached to the plate when you had the fuel pump apart?

Did you also clean the carb, or just work on the fuel pump?

Customer: replied 3 months ago.
Spring is on an I washed it out made sure no port or the jet was stopped up
Expert:  Charles replied 3 months ago.

Did you also open the primer pump?

Customer: replied 3 months ago.
replaced it from parts out of oem kit. It was doing this before so I thought it needed a diapham and the only way I could get was buy a kit.
Expert:  Charles replied 3 months ago.

Do you know the compression on the engine?

When was the last time that it ran correctly?

Customer: replied 3 months ago.
Man I really don't know I just bought it from a guy bout 3 weeks ago and haven't checked compression. But it runs good if you pump the bulb
Expert:  Charles replied 3 months ago.

Ok, is the carb on or off the engine currently?

Customer: replied 3 months ago.
Well I pulled it off to replace the base gasket in process of putting back on. Do I need it off or on?
Expert:  Charles replied 3 months ago.

Good it is off. Make sure that when you are installing the base gasket that you line up the hole in the gasket with the small hole on the block.That is the pulse hole for the fuel pump. If it is blocked, the pump will not work.

Customer: replied 3 months ago.
sir it's lined up.
Expert:  Charles replied 3 months ago.

Did you notice of the old one was?

Expert:  Charles replied 3 months ago.

Since its off, open the bowl and make sure that the needle is not stuck in the seat.

Customer: replied 3 months ago.
Everything looks fine
Expert:  Charles replied 3 months ago.

might as well give it a shot and see if it will run.

Customer: replied 3 months ago.
Also will a flywheel ring and stator on 89 model 20hp mariner work on this motor?
Expert:  Charles replied 3 months ago.

No they wont. they are different part numbers.

Customer: replied 3 months ago.
It ran for 7mins died have to pump bulb and tank has to be up on the bench ssat
Customer: replied 3 months ago.
Seat*
Expert:  Charles replied 3 months ago.

Open the cap on the fuel tank and see if it will run better.

There is water going to the engine, right?

Customer: replied 3 months ago.
Oh yea I got muffs on it with water on lol
Expert:  Charles replied 3 months ago.

Just making sure.

Customer: replied 3 months ago.
Ran for 7 mins again and died?
Expert:  Charles replied 3 months ago.

With the cap open?

When you prime it up, do you hear any hissing from anywhere?

Customer: replied 3 months ago.
No hissing. I got line from tank straight to carb bc I thought maybe the quick disconnect might not been making a good seal letting air get in
Expert:  Charles replied 3 months ago.

Going to need that compression test.

Customer: replied 3 months ago.
I don't see how it could be a compression problem? It runs too good.
Customer: replied 3 months ago.
sir. The spring is real stiff,is that normal?
Expert:  Charles replied 3 months ago.

Yes that is normal.

Customer: replied 3 months ago.
I'm gonna go get a gauge to ck compression. What is compression is good?
Customer: replied 3 months ago.
It has 120 on both cylinders
Customer: replied 3 months ago.
What else could it be?
Expert:  Charles replied 3 months ago.

That is good.

What did you install on the other side of the plate from the spring?

Customer: replied 3 months ago.
Just gasket on carb side.
Expert:  Charles replied 3 months ago.

How does the fuel filter look?

Will it run under throttle, and just not idle?

Customer: replied 3 months ago.
Filter is clean. Seems like it runs longer under throttle
Expert:  Charles replied 3 months ago.

Ok, when you installed the spring and the ball for the primer pump, where was the ball located?

Customer: replied 3 months ago.
On top of the spring
Expert:  Charles replied 3 months ago.

Ok, are you sure that it stayed there?

What is the RPM at idle on the engine?

Customer: replied 3 months ago.
Yea the ball is on top. I filled the bowl up with carb cleaner pushed the primer and it works. Idle higher then then normal. Don't have a tach its on a duck boat.
Expert:  Charles replied 3 months ago.

is the carb off again?

Customer: replied 3 months ago.
Naw still on motor
Expert:  Charles replied 3 months ago.

Ok, I was going to have you inspect the reeds and a divider on the reed plate.

Your idle in gear in the water should be around 850 RPM.

Customer: replied 3 months ago.
Is it easier on motor to put boyesen reeds in it? And how much more power you think it will give it?
Expert:  Charles replied 3 months ago.

They are simple to install, you may get a few extra ponies, not many.

Customer: replied 3 months ago.
Is the reeds what the vacuum works off of for the fuel pump?
Expert:  Charles replied 3 months ago.

No the piston is. The reeds control the fuel charge going into the engine.

Customer: replied 3 months ago.
what you think I need to try next?
Expert:  Charles replied 3 months ago.

When you swapped tanks, did you also swap hoses?

Customer: replied 3 months ago.
I guess it don't pull vacuum it pushes air to the fuel pump?
Customer: replied 3 months ago.
I just got some new 3/8 gas line when I swapped tanks bc the old line looked like the liner was trying to break down
Expert:  Charles replied 3 months ago.

Yes. As the piston moves up and down, it generates a pulse that drives the fuel pump.

did you get a new bulb as well?

Customer: replied 3 months ago.
Naw I haven't replaced the bulb bc pressures up tight?
Expert:  Charles replied 3 months ago.

If the fuel line was coming apart, guess where the stuff from before the bulb winds up..

Customer: replied 3 months ago.
But I haven't seen any trash in the filter. If it was bulb why would it run long when you bring rpms up?
Expert:  Charles replied 3 months ago.

Because the fuel pump draws harder at higher rpm than at idle.

Customer: replied 3 months ago.
what do I need to try next?
Expert:  Charles replied 3 months ago.

Can you run a straight line from tank to the engine? See how the engine runs then.

Im off to bed now. Talk tomorrow.

Customer: replied 3 months ago.
Does the same with it ran straight to the carb
Expert:  Charles replied 3 months ago.

Was that without the primer bulb?

Customer: replied 3 months ago.
Naw. I don't know how it would get gas to it without the bulb?
Expert:  Charles replied 3 months ago.

If the carb is already full, the pump would draw it in, that is what it is supposed to do.

Customer: replied 3 months ago.
Went ran it on lake it runs great wide open 33-34 mph just won't idle runs out of fuel
Expert:  Charles replied 3 months ago.

Wow, you got 34 MPH out of a 25, thats great. How many turns from a light seat is the mixture needle?

Customer: replied 3 months ago.
Bout quarter of a turn from being all the way in.
Expert:  Charles replied 3 months ago.

Back it out to 1 1/2 turns. that is the starting point.

Customer: replied 3 months ago.
Does that have anything to do with what the pump pulls from the tank?
Expert:  Charles replied 3 months ago.

No, but it does control the idle air/fuel mixture. Will not effect the engine at WOT.

Customer: replied 3 months ago.
Then that's not gonna fix it from not pumping gas at an idle. Lol
Expert:  Charles replied 3 months ago.

It will help the engine idle, and you may not need to pump the bulb any longer.

Customer: replied 3 months ago.
Tried it idles too high slams in gear.
Expert:  Charles replied 3 months ago.

Back off the adjustment on the throttle arm. Lower the idle that way.

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