omc cobra 5.8 overheat at idle

[dude2]

just today, i left the boat idling while i went to park the trailer. When I came back, the temp gauge was peg to hot, i shut it off and on several time, and notice the gauge fluctuated. Thought maybe it might just be the gauge, so i took off close to shore and the temp gauge was about 3/4 of the way, the faster i went the more the gauge returned to slightly lower then half, even stopped working at times. next morning on the way back, it never overheated but the gauge still doesn't work at times. I'm worried if my engine really got overheated, should there be a signal/beep when it does get overheated? Also did I do anything wront letting it idle? I am a new boat owner and like to know where to start looking for signs of overheating. thank you..90' seaswirl sable 5.8l omc cobra....reverse also doesn't engage until several tries and makes ratcheting sound, I am checking forums on omc shift cables issues at the moment. thanks again.

 

[jerryjerry05]

Re: omc cobra 5.8 overheat at idle

My opinion is NEVER leave a boat running by itself EVER!!! That's when it seems to do bad things.
If it's a 90 model it's probably time for new risers and maybe new manifolds.
The shift mechanisim probably needs to be cleaned.
The bellcrank (#42)area loads up with crap and won't allow full travel and thus no shift.Take it apart making sure it goes back the way it came.J

 

[haulnazz15]

Re: omc cobra 5.8 overheat at idle

My first move would be to put in a new temperature sender. That is a cheap part that may solve the problem. When the engine was overheating, did you try putting a hand on the manifolds to see if they were really hot?

 

[bruceb58]

Re: omc cobra 5.8 overheat at idle

Before I bought a new sender, i would buy an IR gun and make some measurements of the thermostat housing where the sender is located.

 

[4Winns2]

Re: omc cobra 5.8 overheat at idle

Did you check the engine to see if it was hot? If it was, you wouldn't be able to put your hand on the risers without getting burned.

BTW: I just flipped my lower shift cable on my 4.3 Cobra. I'm in the adjustment phase now but if you have questions I'll try and help.

 

[dude2]

Re: omc cobra 5.8 overheat at idle

thanks for all the suggestions, i didn't feel the manifolds, but the thermostat house was really hot. one of my friends suggested maybe my impeller is going bad or i sucked up some sand. I usually beached it on the sand, with at least 3ft of water below my prop. lessen learned i guess, or still learning. i just got my a manual and will try to replace the impeller. will invest in an ir gun and probably just get a new temp sender.