OMC 3.0 Cobra 1986 overheating

[cobra 3.0]

I just bought the boat a few weeks ago and am new to owning inboards and this forum.<br /><br />I read about the impeller somtimes requiring to be changed...Is there supposed to be a small hole in the impeller housing on the left face side? It's round and 1/16" in size. I saw water spewing out towards one side when I started it.<br /><br />My engine started overheating after a slow ride along the river.<br /><br />If the hole is not supposed to be there, can I plug the hole with some kind of product or do I need a new impeller housing?

 

[tylerin]

Re: OMC 3.0 Cobra 1986 overheating

I have a cobra and there is suppose to be a hole in the housing don't! plug it. Change impeller

 

[cobra 3.0]

Re: OMC 3.0 Cobra 1986 overheating

Thanks!!!

 

[MarkJSullivan]

Re: OMC 3.0 Cobra 1986 overheating

It is not supposed to overheat. However, if the idle is set too low then if may overheat after a long idle. Check the specification idle, Mercs tend to slip out of spec...this might get you through the summer, but over the winter, get the impeller changed..its not the hours but the age..<br /><br />good luck

 

[stub756]

Re: OMC 3.0 Cobra 1986 overheating

repalce the impeller on the OMC Cobras its so easy to do. If that doesnt fix it look for restrictions in the cooling system.

 

[stub756]

Re: OMC 3.0 Cobra 1986 overheating

one more thing ourt 88 2.3l was also overheating at low speeds(except when on ear muffs) once it was going about 15-20 mph it would cool right down. it turned out to be the water tube going up to the impeller was out of place... so only when water was forced up it would run coool.

 

[cobra 3.0]

Re: OMC 3.0 Cobra 1986 overheating

Thanks folks! I looked at the impeller and it looks fine. I noticed it had been replaced, since the old one was left in the boat by the previous owner. The old impeller was missing a 'wing'. <br /><br />I took it our yesterday and everything was working fine. Must have been all the shallow water driving in weeds that caused my problem...<br /><br />I did notice that this inboard runs pretty rough on idle until it's warm. It will stall if I try to go off too soon. Is this commmon with this type of engine? <br /><br />I had changed the oil with a good quality 10W30, put in new platinum spark plugs and cleaned the air filter and carb with regular car carb cleaner spray (because it ran rough on idle when I got it). These changes did little.<br /><br />It runs real well when it's warm though.

 

[shadowdwpp]

Re: OMC 3.0 Cobra 1986 overheating

I'm a relitively new owner as well but everything I have read says you should use straight 30w oil in an OMC 3.0