Help 99 Johnson 90 hp smokes and idles rough

milom

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Nov 1, 2003
Messages
15
This is my first post but I've been gathering some great info from here for awhile now. You guys sure know your stuff. Anyways the motor is a 99 Johnson 90 hp with the oil injection system and it has become hard to start, smokes and idles rough (dies usually) after start up. If it doesn't die and I give it alot of throttle the smoking will quit and it runs fine until shutoff then it starts doing the same thing again. From what I've read on here it sounds like a VRO pump problem but how do you determine if it's the fuel or oil part thats the problem? Would the fuel or oil line primer bulb loseing prime tell which part was bad? It smokes so bad that you can't work on it while it's running. I use the correct start up procedure so that's not the problem. Any ideas or suggestions would help.<br /><br />Thanks
 

backdraft

Petty Officer 1st Class
Joined
Dec 29, 2002
Messages
266
Re: Help 99 Johnson 90 hp smokes and idles rough

Milom, what brand of oil are you using? nevjb
 

milom

Cadet
Joined
Nov 1, 2003
Messages
15
Re: Help 99 Johnson 90 hp smokes and idles rough

Walmart brand Supertech
 

fcryon

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Dec 1, 2003
Messages
17
Re: Help 99 Johnson 90 hp smokes and idles rough

In the older evinrudes, when an oil pump gives out the engine will just suck the oil directly from the oil resevoir at a fast rate. It sounds like that is what is happening to your motor. <br /><br />Simple check; disconnect the oil resevoir and run a tank of gas premixing the oil. She should run fine and then you know the problem.
 

R.Johnson

Rear Admiral
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Sep 24, 2003
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4,446
Re: Help 99 Johnson 90 hp smokes and idles rough

While running the engine on pre-mix, disconnect the oil line at the motor, and connect a length of clear plastic hose, 1/4 in. dia. by about 2 Ft. long. Tie strap the clear hose to a yard stick, or ruler, and fill with oil. With the engine running, the oil level should drop an inch every 5 or 6 pulses of the pump. Sounds like yours will do a lot more that that. Before replacing the pump, check all of your hose fittings. Restricted fuel, such as a faulty anti-siphon valve in the fuel tank, or an air leak into the fuel pump can cause this also. Check the in-line fuel filter if the engine has one. The service manual shows this test, and has a pretty good trouble shooting section on this system.
 

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: Help 99 Johnson 90 hp smokes and idles rough

Hi, Milom.<br /><br />Just a thought.<br /><br />Are you shutting your engine down by disconnecting the fuel line?<br /><br />If you do that, the oil pump will continue pumping oil into the carbs after the fuel flow stops. When you start her up again later, the excess oil will make it smoke heavily and run rough until it is burned off.<br /><br />Good luck. :)
 
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