Johnson 150 troubleshooting

[seafoxjohnson]

I have a 99 Johnson 150 Ocean Pro that's recently developed a problem. Once the engine has warmed up and been running about 20 minutes or more, the engine starts to run rough and quits on me. When I restart the engine it generally fires right up but idles very high (3000 rpm) in neutral, and then when shifted into gear, the engine runs very rough (sputtering and vibrating). The more throttle I give it, the rougher it runs, and past a certain point in throttling up it dies entirely. I have already changed the plugs and the ignition switch, but neither seemed to help. Any guidance on this would be appreciatied.

 

[Hooty]

Re: Johnson 150 troubleshooting

Mr. Johnson,<br />Welcome to iboats. <br />When the engine starts to run rough, squeeze the fuel bulb and see if this effects the engine's running. If it does, I'd suspect a faulty fuel pump or possible a leak in the fuel line, causing the fuel pump to suck in air. If the bulb has no effect, try giving the priming switch a bump. This will give the engine a small charge of raw fuel not metered through the carburetors. If this effects the engine's performance, I'd guess you need a carburetor cleaning and rebuild. If nether of these produces results, get back to us with this same post.<br /><br />c/6<br />Hooty

 

[Cricket Too]

Re: Johnson 150 troubleshooting

seafox....It sounds to me like you have a problem associated with temperature. It sounds like once you get to normal operating temp. you are dropping some cylinders, moist likely due to an electrical problem, which is why it is running rough. A little advice though, do not attempt to put this motor in gear at 3000 RPM, if you continue to do that you will destroy your lower unit and have more problems on your hand. Sometimes ignition coils will drop out when they get hot and are old and going bad. Since it sounds like you have more than one cylinder dropping out, it may be a little more involved than that and you are going to have to do some troubleshooting, get a factory service manual and it will give troubleshooting tips, I'm sure some of the real experts will chime and help you out as well. Good Luck.

 

[jim dozier]

Re: Johnson 150 troubleshooting

I think Hooty is on to something with the fuel pump. However, your description sounds to me a its running rich. It may be that the fuel pump diaphragm is leaking fuel into the crankcase rather leaking air into the fuel system. It all depends on where the leak is. My guess is that the cylinder to which the fuel pump is attached is not firing well and because its running rich it gets worse as it warms up. Either way, check the fuel pump.

 

[rickdb1boat]

Re: Johnson 150 troubleshooting

Also, check all the fuel lines for air leaks.

 

[seahorse5]

Re: Johnson 150 troubleshooting

Most likely you have an OIS infra-red sensor (electric eye) going flakey as it warms up. It is what tells the computer in the ignition when to fire. It is around $50 and easily replaced by a QUALIFIED tech or by a mechanically inclined individual with an understanding of the service manual. Those screws on the top are not Phillips head, they are Pozi-Drive and you need a special screwdriver or bit to keep from tearing up the head.

 

[fishfool]

Re: Johnson 150 troubleshooting

sea fox i have the same motor 1999 johnson 150hp ocean pro,i only had it a short time and would like some feed back on that motor if you have the time. What is your average full use per mile ? have you had any other problems with it? mine seems to be using to much oil,and i just changed a thermostat that was stuck open.