surging 48hp 1994 Johnson, more info

[roccos]

Here's the latest on my surging problem.
With engine turning 5000-5200 rpm engine runs fine for 5 minutes or so then starts to surge and lose power. I reach down and the primer ball is soft. I give it a few squeezes and the engine picks up and runs fine for another 5 minutes.
There is no inline or water separator filter. I pulled out the screen in the fuel pump and blew it out. No difference.
Plugs new, compression good, Fuel and fuel tank clean. Hose connections are tight. Carbs rebuilt 2 years ago, they look good.
Any help is greatly appreciated.

 

[roger3645]

Re: surging 48hp 1994 Johnson, more info

Sounds like it may be the fuel pump.

 

[roccos]

Re: surging 48hp 1994 Johnson, more info

Would that cause the bulb to go soft?

 

[kenmyfam]

Re: surging 48hp 1994 Johnson, more info

The bulb should remain firm if the motor is getting enough fuel. If it is not then it will not. Probable cause in my opinion is the fuel pump. Many experts out here that will either agree with this or give you another opinion. Keep watching.

 

[tashasdaddy]

Re: surging 48hp 1994 Johnson, more info

kenmyfam, i beg to differ, the bulb will remain firm until the fuel pump starts pumping, then it will become it's normal feeling. why because the bulbs, function is to prime the system. that is to pressurize the system between the bulb and motor, forcing gas thru the fuel pump, fill the carb bowls, and gas to the primer solenoid. once the motor is running, the fuel pump is sucking fuel thru the bulb.


sure sounds like fuel starvation, whether fuel pump. clogging high speed jets, vent on fuel tank, float needle sticking.

 

[roccos]

Re: surging 48hp 1994 Johnson, more info

kenmyfam,
You're right about the bulb, after the engine runs the bulb should feel normal not hard.
Today, I took the carbs apart, cleaned and blew out the jets, checked float levels, etc. The carbs looked very good, no stale gas or varnish. Replaced all hose clamps on fuel lines. Cleaned the screen in the fuel pump (there are no other filters in the system). I'm going to replace the portable fuel tank and hose to the engine.
I'll let you all know how I make out. If still a problem I'll replace the pump.
Anyone else with comments or info please let me hear them.
Thanks,

 

[ezeke]

Re: surging 48hp 1994 Johnson, more info

Did you check the vent on the fuel tank?

 

[kenmyfam]

Re: surging 48hp 1994 Johnson, more info

Sorry if I misled with my explanation. By saying "firm" I meant neither hard nor deflated. Sorry for any misunderstanding.

 

[roccos]

Re: surging 48hp 1994 Johnson, more info

Kenmyfam, I knew what you ment.
ezeke, I did check the tank vent. It's open and clear.
I'll try to get the boat in the water tomorrow.
Thanks,

 

[fishmen111]

Re: surging 48hp 1994 Johnson, more info

I'm with roger on this. Sounds like the fuel pump if it's not the vent.

 

[roccos]

Re: surging 48hp 1994 Johnson, more info

I took the boat out today. Same problem.
Here's what I did so far. Cleaned carbs, replaced tank and hose, cleaned screen in fuel pump, replaced plugs.
I will rebuild the fuel pump next. Where do I get fuel pump rebuild kit.
Any thoughts???

 

[ezeke]

Re: surging 48hp 1994 Johnson, more info

You can get a fuel pump rebuild kit here: http://www.iboats.com/mall/partfind...gd_poid=109270&gd_row=52&**********=522168500

Before you do that, make sure that the gasket between your fuel pump and the engine is absolutely air-tight.

Also you did not say, but did you get a new primer bulb that is made by/for a major outboard manufacturer?

 

[Silvertip]

Re: surging 48hp 1994 Johnson, more info

Do not replace anything until you check the fuel tank pickup. If you are using a plastic tank, debris from the molding and drilling operation can plug up the pickup causing the starvation. I have a habit of checking those tanks at stores when I go by them and nearly every one has at least some plastic debris in them. How do I know this might be a problem. I had that issue myself. On two of my plastic tanks. If that's clear, then go after the fuel pump. There is no reason to change the bulb and lines if the bulb firms up. The only thing that goes wrong are the check valves in the bulb or the clamps at fittings leak air. If the bulb firms up when squeezed its likely ok.

 

[roccos]

Re: surging 48hp 1994 Johnson, more info

took the fuel pump apart. One of the check vavles was broken. Could not get a rebuilding kit so I bought a new pump. Ran it today and seems to be OK.