1990 5.8 cobra idle problem

[madoxx]

I have a 1990 four winns 5.8L w/cobra outdrive. She idles well for about an hour, then, won't idle. She will idle again, after sitting for 1/2 hour or so. She runs all day at cruise,(3700rpm) The temp gauge never gets over 200...Do you think it is a temp problem....or a fuel problem. Have changed out the fuel seperater. Put heet in the tank. She is a fresh water boat with only 188 hours on her. She has sat for most of last year. I just don't understand why after sitting she idles again?<br />Any help would be greatly appreciated.<br />Thank you,<br />Joe

 

[snapperbait]

Re: 1990 5.8 cobra idle problem

Going out on a limb, I'd guess the ignition coil may have a fault caused by engine heat... Maybe a little vapor lock going on? I dunno?<br /><br />Your temp gauge should not even get close to 200 degrees... Should be a 160 degree thermostast, so temp should never get above 180... Ya might be due for a waterpump kit.. How long has it been since the waterpump was serviced last? Waterpump needs a new impeller about every two years..

 

[madoxx]

Re: 1990 5.8 cobra idle problem

Thanks snapper,<br />I pulled my tstat, and replaced my impeller. Still does the same thing. My coil does get very hot..should it?<br />Thanks<br />Joe

 

[madoxx]

Re: 1990 5.8 cobra idle problem

and yes, I know I have to put the tstat back in, I had to order it, and am only using the boat for testing. But I just don't get it, it runs fine at speed, and idle, for awhile, then runs fine at speed, but idle becomes rough and dies. Great for <br />no wake zones! going to replace the coil...talk to you soon, thanks, Joe

 

[akriverrat]

Re: 1990 5.8 cobra idle problem

when did you last see the inside of your exhaust manifold/riser/neck? those plugging up will cause overheating in otherwise healthy cooling system. this sounds like it could be an overheating issue.

 

[madoxx]

Re: 1990 5.8 cobra idle problem

I would agree whole heartedly....except I pulled my thermostat completely out, temp never got over 110 on my test run...exact same effect. Runs fine for the first 1/2 hour..then...after running at cruise for 15-20 minutes...will not no wake idle, or idle at all for that matter. Put in a new impeller, then ordered a new tstat....but, now I know it is not heat! have no idea what to do next.