Fuel bulb tightness

viciousfishes · Feb 17, 2011

Hey guys,

I have a 68 20 horse Johnson. Ive been having problems with power on my boat and now Im leaning towards the fuel pump. I have noticed when I'm runnig the boat the bulb doesnt stay "tight". It feels like it has a decent amount of slack in it and Im wondering how tight it should feel while running. If its not tight would this mean that maybe my fuel pump is bad? I was thinking that the diaphrams might just be warn out.

Now... Fellow gearheads... give me your input!

HighTrim · Feb 17, 2011

Re: Fuel bulb tightness

Your bulb will not be "hard" while underway.

Describe your power issues in more detail. Have you lost top speed, acceleration? Have you started by ensuring you are sparking on both cylinders? What is the compression of both cylinders?

boobie · Feb 17, 2011

Re: Fuel bulb tightness

Your primer bulb will not feel tight when running. Only when first start priming. After running it's part of the fuel line.

5150abf · Feb 18, 2011

Re: Fuel bulb tightness

Unlike a car that pumps the fuel from the tank to the engine your outboard pulls the fuel to the engine so as soon as you start the boat it releaves the pressure in the bulb, so it actually runs a slight negative pressure, completely normal.

Is it running badly or the the bulb just doesn't stay hard?

viciousfishes · Feb 18, 2011

Re: Fuel bulb tightness

It just has sporatic power loss once It reaches normal operating temperature. (I think its temp related but not sure) It will run like a champion and then its just like a switch turning one cylinder on and off with no particular pattern after its reached that temperature.

eavega · Feb 18, 2011

Re: Fuel bulb tightness

That sounds like something electrical that is expanding when the engine warms up. If I recall correctly, the 68 20 HP only has one carb, so if you were having a starvation issue it wouldn't just cut out on once cylinder. Look to see if you still have spark when the engine starts dropping that cylinder, and if so you may be able to determine the faulty component.

Rgds

lindy46 · Feb 18, 2011

Re: Fuel bulb tightness

If it's pumping water ok, then you probably have a bad coil which results in intermittant fire on one cylinder.

HighTrim · Feb 18, 2011

Re: Fuel bulb tightness

Inductive timing light while underway would be the best way to troubleshoot this.

viciousfishes · Feb 18, 2011

Re: Fuel bulb tightness

Is there any way to find out what cylinder it is dropping? Gaining that knowledge would greatly increase my advantage. And yes, it is only one carb.

viciousfishes · Feb 18, 2011

Re: Fuel bulb tightness

And does anybody know if it has two coils or just one?

HighTrim · Feb 18, 2011

Re: Fuel bulb tightness

Inductive timing light, as mentioned above. Hook it up to a plug wire, and run until you experience your power loss. If the light stops flashing, you have found your trouble cylinder. Just be careful when doing this, dont want to be out there in choppy water by any means.

2 coils, 1 for each cylinder. Have a peek at them, if they are cracked or damaged, very likely your issue, and need to be replaced. You will know very quickly when looking at them.

viciousfishes · Feb 18, 2011

Re: Fuel bulb tightness

Your the man.

You may have just solved my problem and made my life a lot easier. I have tried everthing except this and the only reason for that is because I dont have a flywheel puller. Im going to get one tomorrow and I'll take a look at everthing.

lindy46 · Feb 18, 2011

Re: Fuel bulb tightness

viciousfishes said:
Is there any way to find out what cylinder it is dropping? Gaining that knowledge would greatly increase my advantage. And yes, it is only one carb.

Pull plug wires off when running, one at a time, when it acts up. One wire will make no difference (the one with the bad coil), and the other wire with the good coil will kill the engine. Don't get shocked!

boobie · Feb 18, 2011

Re: Fuel bulb tightness

I'd recommend pulling plug wires off when running first. That way you'll know what cyl is acting up before taking apart.

viciousfishes · Feb 18, 2011

Re: Fuel bulb tightness

Im putting new coils on it tomorrow. Ill let yall know what happens

HighTrim · Feb 18, 2011

Re: Fuel bulb tightness

Be very careful when pulling plug wires while on the water, I hate reccomending that, as I have seen someone seriously injured from the flywheel when the boat hit a wave, and he fell into it. I find the inductive timing light with a long lead to be much, much safer.

boobie · Feb 18, 2011

Re: Fuel bulb tightness

If your going to use the timing lite it should be said to look into it and look for black spots. That's when the cyl is not firing. I still use the insulated pliers to pull plug wires but what do I know, only been doing it for 45 yrs.

viciousfishes · Feb 19, 2011

Re: Fuel bulb tightness

Alright so I have a pretty beefy 3 jaw puller that fits really well on the flywheel. I have a repair manual book for my motor and it says not to use any other puller other than a flywheel puller of I might damage the flywheel. Has anybody pulled a flywheel with a 3 jaw before?

Ill wait on a response untill I start pulling

wilde1j · Feb 19, 2011

Re: Fuel bulb tightness

Get a harmonic balancer puller. Other thqn the OEM puller, it's the ONLY one to use. See the sticky about the details like using only Gr8 botls and washer, etc.

SparkieBoat · Feb 19, 2011

Re: Fuel bulb tightness

Boobie..how have you been doing this for 45 years when you are only 27 years old...I can add and that dont add up.....

got to pull the flywheel to change the coils???

Fuel bulb tightness

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