Johnson Surging at high RPM's....

[Knightime]

1995 200 Johnson...You guys have been great helping me with this motor so, I thought I would run this by you.<br /><br />The motor sputters a bit at idle but runs good and always starts. Surges at high rpms above 5k.<br />I'm thinking I have a fuel restriction - when I pump the ball or press choke the problem gets better and/or goes away. I have not yet changed the water seperator and I suspect this is my problem.<br /><br />Here is my question....could the VRO cause surging?<br />I'm new to Johnson and was told the VRO's are unreliable so I am not using the VRO for oil distribution, I am mixing the oil.

 

[OBJ]

Re: Johnson Surging at high RPM's....

Might be sucking some air into the system Bill. Take a look at the fuel lines and make sure all are tight. <br /><br />Is the oil line from the VRO still connected up to the nipple on the engine pan? If so, does the nipple have a rupper cover over it? This is to prevent air from getting into the pump via the oil pump side of the VRO.<br /><br />Make sure the fuel tank is vented also.<br /><br />The pump has a hose leading back to the block through a pulse limiter. Make sure these connections are tight also.<br /><br />Was there a particular reason why you disconnected the oil pump or was it just on "advice"?

 

[Knightime]

Re: Johnson Surging at high RPM's....

No Particular reason the oil pump was disconnected. Simply recommendation....<br /><br />Did I do wrong? What's your recommendation with the VRO's?<br /><br />Thanks,<br /><br />Bill

 

[OBJ]

Re: Johnson Surging at high RPM's....

This has always been a topic of discussion here on the forums Bill. The first VRO's that came out from OMC were metering pumps that varied the rate at which oil was injected into the fuel depending on the rpm. No alarms were associated with the originals and when the pump failed to oil the owner didn't know it until it was to late.<br /><br />Subsequent pumps had alarms to warn of low oil in the reservoir and no oil/restricted flow. But the early days of the pump gave the pump....not so good a name.<br /><br />The newest pumps are just oil metering pumps and give a 50:1 ratio nearly through the rpm range....slightly less on the low end.<br /><br />But the early days really gave the pumps a bad name and it stuck. I have an 86' 90hp with what is now "OMS" or Oil Metering System. Personally, I like them. Many do....many don't.<br /><br />No, I can't say you "done wrong". Many engine owners will disconnect them and mix their own oil. Guess it's just what makes you feel best.<br /><br />My own feeling is, if you make sure the alarms work, mainly the oil restriction/no flow alarm, I'd run it with the OMS connected.....but that's just my opinion.<br /><br />An OEM manual for your engine will tell you how to test the pump and alarms to keep it in top form. One thing about them, if they do go bad on the water, you can always disconnect the oil end of the pump and mix the oil from the oil reservoir into the tank, and get home.

 

[Knightime]

Re: Johnson Surging at high RPM's....

Thanks OBJ, I take your advice seriously.

 

[OBJ]

Re: Johnson Surging at high RPM's....

Well we need to see if we can take care of the surging problem Bill. Check over the fuel system first for air leaks. Do you have any history on the engine....when the carbs were last overhauled, has it set a while before you got it? <br /><br />Replace any fuel lines that are hard. A good fuel line will be plyable when you squeeze it. A hard line can lose it's grip on connections and suck air.<br /><br />Couple other things since the engine appears to be new to you, check the engine temp at idle, make sure it's getting up to temp.

 

[Knightime]

Re: Johnson Surging at high RPM's....

History of the motor. I just bought it. It was rebuilt. <br /><br />Checked through the fittings today. Pumped up the bulb tight and there did not appear to be any leaks.<br />The rubber cap used to block off the oil line was not leaking BUT DID HAVE A CRACK IN IT. Appears to be older and brittle.<br /><br />After this work I was not able to test the boat and probably won't be able to drop it in till next weekend....<br /><br />Additionally, most all the lines are attached with zip ties and to get to them I'll have to drop the pan.

 

[Knightime]

Re: Johnson Surging at high RPM's....

OBJ,<br /><br />Back to my surging problem. I went through each line to and replaced most everyone. I can pretty much rule out a restriction or air leak. Followed your advice.<br /><br />Again, The motor idles fine, begins surging above 5k. At this RPM, the fuel pump ball becomes soft, if you pump the ball the surging stops......<br /><br />I have not tested the VRO, could this be the problem? <br /><br />Any other ideas?<br /><br />Thanks,<br /><br />Bill

 

[MarkV_Deep6]

Re: Johnson Surging at high RPM's....

The fuel pump ball is the key to your answer. This should not be caused by the VRO pump. They work in conjunction with each other but one does not make the other have restrictions per sey.<br /> I would go back and check all things up to the pump bulb.... there's gotta be a restriction there somewhere, you mentioned the water seperator,did you change the filter or check it yet, what size are the fittings on all the connections in the line 1/4 or 3/8, is the bulb a 3/8 size? I know if any thing on my V8 restricts at all there will be problems with the fuel supply. The setup for mine does not provide for a pump bulb as this restricts flow.<br /> You mention that this is a rebuilt engine..What did it replace? The fuel delivery system may need to be upgraded if you have the supply hoses that would have supplied a less fuel demanding engine.

 

[Solittle]

Re: Johnson Surging at high RPM's....

If this is a carbed engine you may have a bit if crud in the carbs.

 

[OBJ]

Re: Johnson Surging at high RPM's....

In addition to Marks advice, check around the bowls for any exsessive leaking. The bowls are plastic and prone to warpage. Makes a nice mess in the pan. <br /><br />Just a thought....is the oil supply hose in the pan area still connected up to the pumps oil connection?

 

[Knightime]

Re: Johnson Surging at high RPM's....

Carbs are totally rebuilt....they are not leaking.<br /><br />I have not went back as far as the fuel tank. (other than checking the vent).<br /><br />I changed the sperator and even tried bypassing it.<br /><br />Fuel line size from the tank to the water separator is 1/2. From the Separator to the bulb and to the engine it is 3/8.<br /><br />I will double check the oil supply hose in the pan area to ensure it's connected but I'm 90% sure it is correct.