70hp johnson 4 stroke

[steve1875]

I've recently purchased a 98 pontoon with a Johnson 70 hp 4 stroke fuel inj. engine. It had been running really good the first couple times i took it out. The last trip it ran very rough and would not idle, and eventually when i would throttle down on it, it would "fall on it's face" like and old carb. engine. It would bog down and hardly move at all. I'm not much of a mechanic but i thought for sure it was a fuel issue( and it still may be) and i went thru the fuel system changed out the filters, took out the injectors and inspected them(they visually looked fine), I checked the high pressure fuel pump screen, and nothing i saw had any evidence of trash in it. I also went ahead and changed the oil and filter and also the spark plugs. Any suggestions???????
Need some help..

 

[EGlideRider]

Re: 70hp johnson 4 stroke

You've done about all a laymen mechanic can do. Take it back out, and if it still acts up, take it to a competent professional.

 

[lmuss53]

Re: 70hp johnson 4 stroke

Check the ethanol blend fuel for water. I had similar issues with a carbed 2 stroke last year and it was the fuel. I dumped it all in my pickup where it burned OK, and made sure to use most of the fuel every trip so I could always have fresh fuel for the boat.

 

[steve1875]

Re: 70hp johnson 4 stroke

ok, thanks for the info..

 

[Silvertip]

Re: 70hp johnson 4 stroke

If your boat has a water separating fuel filter (looks like an oil filter) replace it. If you don't have one, install one. EFI/DFI engines should have one because of the moisture issues associated with ethanol blended fuel as well as marinas that tend to have water in their fuel supplies.

 

[Rancherlee]

Re: 70hp johnson 4 stroke

Did you remove the drain screw on the fuel vapor separator? Its the aluminum housing that the high pressure fuel pump is inside. I drain mine once a year as that is where the water likes to collect in the fuel system. you can reach the screw with a longer phillips between the intake runners to bleed it out.

 

[steve1875]

Re: 70hp johnson 4 stroke

Yes i actually did. I really thinking now that it may be the fuel pump going out. I'm going to check the pressure on the system and try and verify that's the problem. Appreciate the info.

 

[acad]

Re: 70hp johnson 4 stroke

I had a 40hp Honda. Jets would clog during periods of non use. When I finished using the boat, I had to disconnect the fuel line and run the engine until it stopped. Once I started doing this, I never had another problem. I won't scare you with the amount of money I paid to have jets cleaned or replaced and tune up!