final overheat question

[jmarine225]

I keep trying to ask this question and am brought to different ideas. I have an OMC Cobra 1993 5.8L. I had an overheat problem, did all the trouble shooting and it appears to be running good now with a max temp of maybe 175 (i have a 160 t-stat). My question is since my temp gauge is reading okay do I still need to be concerned about the temp of my risers or manifolds? I figured if there was some sort of blockage in those it would somehow show an increase in temp on the gauge. Please don't tell me all the different trouble shoot options as I have completed them all and just have this one question. Thanks.

 

[jtybt]

Re: final overheat question

If you have Full FWC, you can still have a blockage in the riser raw water out-flow and burn your rubber connections and crack cast iron elbows and still show normal temps.

 

[jmarine225]

Re: final overheat question

Thank you very much for your answer. I had a hard time hearing that from someone. I wasn't sure if the risers/manifolds had a blockage if it in turn would show up on the temp gauge. I will remove my risers and begin cleaning them up to get through the remainder of the season and plan on getting new manifolds in the off season. One more question though. Do you have any idea what the temp of the risers should be when running normally? I heard people say you should be able to touch them, to touch them for a few seconds to, not be able to touch them, so I'm just looking for a straight forward answer....if there is one. Thanks.

 

[HT32BSX115]

Re: final overheat question

Thank you very much for your answer. I had a hard time hearing that from someone. I wasn't sure if the risers/manifolds had a blockage if it in turn would show up on the temp gauge. I will remove my risers and begin cleaning them up to get through the remainder of the season and plan on getting new manifolds in the off season. One more question though. Do you have any idea what the temp of the risers should be when running normally? I heard people say you should be able to touch them, to touch them for a few seconds to, not be able to touch them, so I'm just looking for a straight forward answer....if there is one. Thanks.

Your engine and manifolds MUST have enough flow capability to get the water in and out.


To get in, it requires an unobstructed water intake, good raw pump and clear (of obstructions) hoses, power steering & oil coolers. If you have closed cooling the "raw side" must be "clear" too.

Then the water MUST have an unobstructed path out..... The only path out (for a V-8) is through the 2 exhaust manifolds AND risers. (Or risers only if [full-sys] closed cooled.

If everything is clear you should be able to put your hand on the risers when it's running......there's probably no definitive temp....but if you've got enough water flow, they won't be REALLY hot when running.

My question is since my temp gauge is reading okay

How do you know this?


Unless you've checked it with a known gage or an infrared temp gage you won't know..

Regards,



Rick

 

[jmarine225]

Re: final overheat question

Okay I'm back to being totally confused again after the last post. You're saying just because my gauge says I'm not running hot my engine could still be overheating? I've used an IR gun to check my temps and at my manifolds and risers I was shooting a temp of around 180. Is that too hot if the gauge is showing in the normal range? I had an overheat from a blocked oil cooler where the gauge kept going up but since I had it repaired when i begin running at WOT it may go up to about 175 or then back down to 160. I don't understand the purpose of checking the temps at the risers when no one knows what the temps should be anyway. Everyone says "shouldn't be too hot". Too hot for me is alot different then too hot for my girlfriend. Or, at what temp will the rubber exhaust hoses blow? I've been running so far about 8 hours and haven't had any problems yet but i'm trying to be preventive from having problems.

 

[HT32BSX115]

Re: final overheat question

since I had it repaired when i begin running at WOT it may go up to about 175 or then back down to 160.

That's within normal range.....

I've used an IR gun to check my temps and at my manifolds and risers I was shooting a temp of around 180. Is that too hot if the gauge is showing in the normal range?

You're fine....Go boating........

 

[jmarine225]

Re: final overheat question

hey thanks for your help. I was finally able to have my question answered

 

[jmarine225]

Re: final overheat question

Sorry, one more thing. On my engine 1993 Omc Cobra 5.8 can I remove the risers to inspect them while the boat is on the water? I'd hate to pull them off and sink the boat Also it is on a Four Winns 245 Vista Cruiser

 

[HT32BSX115]

Re: final overheat question

Sorry, one more thing. On my engine 1993 Omc Cobra 5.8 can I remove the risers to inspect them while the boat is on the water? I'd hate to pull them off and sink the boat Also it is on a Four Winns 245 Vista Cruiser

Well,

maybe.........


With it sitting in the water, find where the water line is. compare that to where the risers will "break" from the manifolds. If it's higher (the water-line) , water WILL enter the boat.

Now having said that, it *should* be much lower ........ but I'd check before I loosen the bolts!!