View Full Version : OMC 460 Running Warm Any Ideas

Daniel Pacheco
06-08-2003, 07:23 PM
I have an 88 omc king cobra 460. It idles at 160 deg F and runs under load at 180 deg F. Never goes any higher? Is this normal operating temp for this engine? It has BRAND NEW manifolds and risers as well as a sea water pump in the outdrive. Any ideas? Anyone have one with raw water cooling have this trouble? I hear that the fresh water closed cooling does not have this trouble?

06-08-2003, 09:32 PM
" Check your thermostat, as it may be either the wrong one or malfunctioning. You are lucky most people cant get their engines to run that cool. The normal operating temp for that engine I am not sure of, but it should run at whatever the thermostat is designed for. The other thing is your temp guage OK. Has it always run at this temp or is this a new problem. Kim "

Daniel Pacheco
06-09-2003, 02:26 PM
" It has always run this way. I have a new temp sender, guage, manifolds, risers, waterpump and raw water pump. These are all new as of this winter and I just replaced the t-stat again and it made no difference!
dan "

06-09-2003, 09:00 PM
" Now I have to ask what is the normal operating temp for this engine? Does your manual say or your dealer. Perhaps someone out there has a similiar engine. HELP!!, Kim "

Daniel Pacheco
06-11-2003, 04:46 PM
The manual does not say. all it says is that the 88 and 89 version of this engine came with a 160 t-stat and the 90 version came with a 140 t-stat. This is why I am confused. thanks

06-11-2003, 11:35 PM
" Just because the thermostat opens at 160, doesn't mean the engine will run at that temp. 170-180 is normal for FWC engines and if it has always run at 180 then so what. 180 is certainly not going to hurt anything. If the water flow is good and you don't have any hot spots in your exhaust system you should be fine. One note on that engine. The 2.3 cobra which has an operating speed of 5600, uses a different impellor. It will fit in place of the standard Cobra impellor, but will not pump as much at lower speeds. This is easy enough to check, so if you want to be certain you don't have the wrong pump installed, you might want to pop the pump apart and take a looksee.
Good luck "

06-12-2003, 05:01 PM
Raw water cooling systems that operate in salt water run at about 140 degrees to avoid salt build-up in the water jacket. Otherwise you can get more efficiency at a higher temperature. 180 is not hot provided you are not operating a raw water system in salt water.

06-12-2003, 10:06 PM
" Mercruiser fresh water cooled engines cool the manifolds with raw water, be it salt or fresh. At 180 degrees. "

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P. Johnson
05-07-2006, 08:39 PM
I have a 1990 30 Hp Johnson J30TELESS long shaft outboard. The engine runs fine but I'm not sure if it is running too hot. I have replaced the water pump and it appears to be pumping fine. Back to my question. After running the engine full out for 10 mins the base of the exhaust housing where it meets the powerhead gets very very hot. If I stick my hand in the exhast/water outlet on the back of the shaft it appears to be around 150 degrees and almost steamy. At idle the engine cools right down. I have owned smaller 9.9 - 15 hpoutboards and the exhaust/water was always just warm. Should it be this hot?