OMC Cobra 5.0 overheating

[bruceb58]

Re: OMC Cobra 5.0 overheating

Didn't pull the manifolds because I figured the condition of the risers would be somewhat indicative of the manifold's (risers were perfect), and the boat has never been in anything but freshwater so I feel that the likelihood of the exhaust components needing replacement is very unlikely.

I would agree with that statement.

If I were you I would verify the temps you are seeing with an IR gun.

 

[sam60]

Re: OMC Cobra 5.0 overheating

I would agree with that statement.

If I were you I would verify the temps you are seeing with an IR gun.

My risers looked OK, all the carp had resided in the inlet tubes. I wouldn't have known by looking at the risers only.

Ck- Bruceb has been through this alot more than I. The IR gun is alot easier than pulling heavy parts. Let us know what you find.

 

[Jono69]

Re: OMC Cobra 5.0 overheating

I would definitely verify the gauge is reading correct before tearing into anything else.

 

[Ck111484]

Re: OMC Cobra 5.0 overheating

Thanks guys, I really appreciate any help I can get.
Will report back what I find with the gun.

The temperature seems to stay very solid at ~190 degrees, so my guess is that I'm getting air bubbles somewhere; the flow of water is steady, but with air diminishing its efficiency, it can only cool the engine off so much.
Total guess, but makes sense to me.

 

[Ck111484]

Re: OMC Cobra 5.0 overheating

Okay, here are my measurements that I took with the infrared gun (not my picture):

The middle box represents the area right around the base of the sender; the sender itself was a bit cooler.
I shot the gun at the top of the block a bit and saw nothing over ~170 degrees.
The whole time, the boat's gauge in the cluster was pointed at ~ 195-205 degrees F.
I also connected a clear tube from the PS cooler to the thermo housing, and the water flow was remarkably clear of bubbles once the engine warmed up, even on muffs.

What do you think? Bad gauge?

 

[bruceb58]

Re: OMC Cobra 5.0 overheating

This on muffs or running under load? The 68? you are measuring on the risers is a lot lower than what I get on my Volvo with brand new risers/manifolds.

What do you think? Bad gauge?

Or bad sender.

 

[Jono69]

Re: OMC Cobra 5.0 overheating

I would replace the gauge. Big difference in temps there. Cheap fix $20 to $50 depending on what you need. Good insurance for the future should it actually start overheating.

 

[Ck111484]

Re: OMC Cobra 5.0 overheating

This on muffs or running under load? The 68? you are measuring on the risers is a lot lower than what I get on my Volvo with brand new risers/manifolds.

Or bad sender.

This was on muffs.
Yeah, I thought it was interesting that the risers were actually cold to the touch. I seem to remember them being hot sometimes. I will continue to keep an eye on them with the gun... it's been officially added to my boat tool bag.
And um, interesting that you mention the sender... the temp gauge stopped working when I bought the boat, and I just ran up to Autozone to get a new sender, and picked one up for a Bronco (Ford 302). I just did a google search, and apparently the marine versions of senders are not the same as automotive.

I think we may have found my problem.
The boat is new to me, and I don't remember what it was reading before the big overheating event on Memorial Day, so it may have been reading this high all along. This is excellent news, because it appears that not only do I not have an overheating issue, but that the temps during my overheat event were not nearly as high as they appeared.
If this is indeed the case, I feel incredibly stupid, and even more relieved.

I would replace the gauge. Big difference in temps there. Cheap fix $20 to $50 depending on what you need. Good insurance for the future should it actually start overheating.

Think I will try a new sender first...

 

[bruceb58]

Re: OMC Cobra 5.0 overheating

I would probably summarize it this way:

 

[Idlespeedonly]

Re: OMC Cobra 5.0 overheating

I dont see how the risers can be colder than the manifolds. The risers are at the end of the flow. So they will always be warmer. Then the huge variation from side to side. I would disregard all of those temps till you get it in the water.

 

[bruceb58]

Re: OMC Cobra 5.0 overheating

I dont see how the risers can be colder than the manifolds. The risers are at the end of the flow. So they will always be warmer. Then the huge variation from side to side. I would disregard all of those temps till you get it in the water.

One manifold is warmer and one manifold is colder. You will get variations from side to side anyway...that is normal.

The whole purpose of the test was to verify the temp reading.

 

[Idlespeedonly]

Re: OMC Cobra 5.0 overheating

Verify what reading? The temp of the thermostat housing will almost always be cooler the the engin temp.This test isn't accurate due to the fact he wasnt under operating conditions. What is the water temp. coming out of the garden hose?

 

[Redrig]

Re: OMC Cobra 5.0 overheating

I just ran up to Autozone to get a new sender, and picked one up for a Bronco (Ford 302). I just did a google search, and apparently the marine versions of senders are not the same as automotive.

Yup, different OHM's from Hot to cold, full to empty, ect.

 

[bruceb58]

Re: OMC Cobra 5.0 overheating

Verify what reading?

He was measuring the temp at thebase of the sender to verify if it was the temp reported by the gauge. The temp for the rest of the engine or incoming water temp is unnecessary to know. You seem to question the validity of the measurement. Why?

 

[Idlespeedonly]

Re: OMC Cobra 5.0 overheating

If The income in water temp was say 70 degrees Then you know the gauge readings are not correct. I have a ray tech infrared gun and I just don't trust them. They are ok, i would trust the factory gage more. Also, once this thing is in the water everything might change

 

[bruceb58]

Re: OMC Cobra 5.0 overheating

If The income in water temp was say 70 degrees Then you know the gauge readings are not correct. I have a ray tech infrared gun and I just don't trust them. They are ok, i would trust the factory gage more.

Since the temp sender is on the engine side of the thermostat and the incoming water doesn't flow by the sender your assumptions are not correct.

If you measure the temp at the base of the sender, you are measuring the temperature that the sender is seeing.

 

[Idlespeedonly]

Re: OMC Cobra 5.0 overheating

If his incoming water temperature is 70 degrees there is no way is manafold temps will be what they are. Which would prove that the temperature readings are inaccurate.

 

[Idlespeedonly]

Re: OMC Cobra 5.0 overheating

Double post. The new mobile version isn't working too good for me

 

[bruceb58]

Re: OMC Cobra 5.0 overheating

If his incoming water temperature is 70 degrees there is no way is manafold temps will be what they are. Which would prove that the temperature readings are inaccurate.

We are talking only about the sender reading. The manifold temps are another story completely.

I trust my IR gauge way more than the dash temp gauge.

 

[Idlespeedonly]

Re: OMC Cobra 5.0 overheating

You're just not getting what I'm explaining. Basically I am just wanted to verify the readings are accurate