ok on trailer-johnson 90 v4

[stevef74]

when my johnson v4 90hp is in water, it will start spitting and usually quit when at idle. but on the trailer, it will idle all day. dealer cleaned carbs & other stuff, but was unable to find problem.<br />i have been told that for this model (1982), the exhaust outlet is too close to water & creates 'back pressure'. but no one has given me a solution. motor runs great at higher speeds.

 

[JB]

Re: ok on trailer-johnson 90 v4

Howdy, Steve. When the leg is in the water there is a very slight back pressure on the exhaust. That causes the engine to want a very slightly richer mixture than when on the trailer.<br /><br />Give your idle mixture jets about 1/4 turn CCW or raise idle speed about 100-200rpm<br /><br />Red sky at night. . .<br />JB

 

[Franki]

Re: ok on trailer-johnson 90 v4

ummm, my exhaust comes out of the prop on my Johnson V4, thats pretty close to the water don't you agree?<br /><br />and you have relief holes on the back of the leg just under the cowling don't you?<br /><br />that seems a very strange explanation for the problem.<br /><br />But mine doesn't idle all that well in or out of the water... (I have a 100HP V4 older then yours.)<br /><br />Anyway, I'd be checking things like the fuel pump and electrics unless you can get more details on the "exhaust" problem, I have never heard of that before.<br /><br />rgds<br /><br />Frank

 

[stevef74]

Re: ok on trailer-johnson 90 v4

thanks-<br />you're right-i believe the exhaust actually comes out at prop. are these relief outlets below the motor?? one mechanic suggested drilling 1/2" hole at these relief outlets to relieve pressure.<br /><br />i'll try setting to richer mixture-not sure how to adjust idle & mixture.<br /><br />i have manual so i should be able to find adjustments.

 

[Dhadley]

Re: ok on trailer-johnson 90 v4

You have fixed idle jets on a 1982 but they can be changed to get a richer idle. It's not totaly uncommon to have to rejet older motors for todays fuel. Just make sure the linkages are all set correctly, you have the correct plugs and are using fresh 87 octane fuel. Sometimes the throttle shafts leak air and can cause a lean idle condition. <br /><br />Drilling the exhaust relief hole will sometimes work but on your motor it's a band aid type deal. It should idle fine if all is OK. <br /><br />That brings up another thought -- If you haven't decarboned in a while, try that first.<br /><br />Good luck!