Omc cobra 4.3 ran out of water now overheating at idle

Estarnes67

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Jul 6, 2017
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18
Ok so I have a 94 seaswirl 180 se with a 4.3 omc cobra. It's my first boat and i love it and only have had it out a couple times. The last time I was at the lake after finishing the day my buddy pulled my truck down the ramp and when I pulled up to the trailer I automatically jumped out to help and forgot to turn off the boat. I had him pull it up the ramp and walked to the back to to pull up the Speedo and realized it was still on and quickly shut it off. It was on out of the water for about 30 seconds. When it shut off a little cloud of smoke came out of the bellow. Didn't think it was on long enough to cause any damage (remember this is my first boat). Next time I had it out it was idling at the dock and got warm but as soon as I put it in gear and start moving forward it goes right back down to normal temp and is fine until I put it in neutral and idle it it heats up again. Not sure what it could be I pulled the impeller housing and everything looks fine. Should I replace it anyways or do you guys have recommendations on where to start troubleshooting? I ran it at home with the muffs on and it was percect no overheating at idle. Any advice and tips is greatly appreciated thanks in advanced.
 

southkogs

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Jul 7, 2010
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I would try the impeller. It sounds to me like you burned it up. It's a service item anyway - so perhaps it was older and you just pushed it over the edge.

Welcome aboard.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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Only takes seconds to toast the impeller without water. I bet the exhaust flappers are toast too.
 

Lou C

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Nov 10, 2002
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11,802
This is a '94 boat, is it the original Cobra with the impeller in the outdrive, or Volvo style with the impeller on the engine? Sometimes a boat will have the prev year's drivetrain.
​I'd at least replace the impeller and wear plate. Not sure if you burnt up the flappers. Maybe not if the engine was running at idle for like 30 sec. At any rate drain the manifolds, remove the risers and check, that's the only way to know.

​Impellers can look fine, but be worn enough to not pump well at low speeds. Same with wear plates, a bit of sand can score them to the point where they do not allow the impeller to pump right.
 

Estarnes67

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Jul 6, 2017
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18
Ok I'll go ahead and replace the impeller and ya it's the cobra drive with the impeller on top. I'll check the flaps and report back with any findings as well thanks guys
 

Estarnes67

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Jul 6, 2017
Messages
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Ok guys I had a new impeller put in housing and all and checked the exhaust flaps and they are fine. Did a lake test and it's still overheating at idle... So I pulled the power steering cooler hose and saw maybe 2 little pieces of the old impeller so I backflushed it from the thermostat hose. I also took out the thermo and am going to check it as well. While I had the thermo housing off I pulled the 2 drain plugs on the block and was just getting drips out of them not a steady flow, is this normal or should it be a steady flow? It took a while for the water to stop draining... any other things I should do or check? Or any opinions on what else it could be? Thanks guys...
 

Bondo

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Apr 17, 2002
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70,465
While I had the thermo housing off I pulled the 2 drain plugs on the block and was just getting drips out of them not a steady flow, is this normal or should it be a steady flow? It took a while for the water to stop draining...

Ayuh,.... Welcome Aboard,.... Ya gotta poke, 'n prod the holes with a nail or screw to knock the crud outa the way,....
 

lasko1

Seaman
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Mar 12, 2012
Messages
67
How high is your Temperature gauge going when you say "overheating"?

I only ask because the same type of issue happened to me, only my buddy shut the hose off while it was on the muffs and now my Temperature gauge reads 180? once warmed up instead of 160?. My gauge now reads 20? higher than what its supposed to be reading. I double verified that my engine temp is only 160? by installing a manual thermometer into the temperature sending units hole near the thermostat. I simply unscrewed the temperature sending unit and my thermometer has 1/2" threads so I just temporarily installed it. I also used an IR gun to shoot the temperature and both read 160?.

Along with clearing the drain holes on your block with something like a nail as Bondo mentioned above, you also need to clear the drain holes on your exhaust risers when winterizing it.
 

Estarnes67

Cadet
Joined
Jul 6, 2017
Messages
18
Ok so I got a pick for the drain holes on the block and got a bunch of crud out till it was a steady flow..and went ahead and put a new thermo in... did a lake test today and it's still overheating..and to answer your question my gauge will go all the way up to 225 if I let it and ya I'm going to verify that with my buddy's ir gun but it will have to be at the lake cause it won't overeat on the muffs...i also plan on removing the risers and checking them out for sure...am I able to take the bypass hoses off the thermo housing and put pressure through them with a garden hose or would water make it's way in the heads or??? I had heard from another forum that the risers are supposed to stay somewhat cooler to where you should be able to keep your hand on them for a short period of time and was wondering if there's any truth to that cause I tried today and they were so hot that I could even hardly touch them? Also was wondering if I could take the top hose off the power steering cooler and backflush out the outdrive or would I have to take the impeller off to do So or? Not really sure.. thanks guys really appreciate it
 
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