OMC Cobra 5.0 overheating

[Idlespeedonly]

Re: OMC Cobra 5.0 overheating

As for the op's polishing. I have used rexco's formula 5 polish. It is designed for cleaning molds. It is amazing how well it works. And the price is very reasonable.

 

[Reinell-BRXL-191]

Re: OMC Cobra 5.0 overheating

Idlespped, are you really going to come in here and tell everyone, that our engines are not just air pumps? and that they actually are creating mass? In a normal car engine, their is expansion created by heat that causes increased CFM, in a water cooled boat engine, this is not true. You can't tell me that if you shove air in to a cylinder, and compress it it, then light it on fire, and actually burn about 75-85% of the oxygen in it, it expands and becomes more air? wow.... my science teachers were all wrong... The engine in my boat has become a nuclear fission machine... Please show us the scientific theory behind this... and while you are doing that, I will be a little nerd with his feelings hurt and go and read every thread you have been involved in... and come back and report what you have said... you're a child... now address the 4 entry points in to the manifold.. yep.. you were wrong... as far as a riser that is further away from the exhaust fire and being water cooled should be hotter, you were wrong..and you are wrong about a boat engine making mass..

An engine, takes that the air drawn in to it, and compresses it, normally to around 10 to 1... this is done by the travel of the piston reaching it's top point in the bore in relationship to the head. Then the gas mixed in to it, which was introduced to the air flow thru a carburetor or injection system on the intake stroke, is ignited,( with a spark plug) this "explosion" forces the piston back down, as the air fueled by heat, expands to it original size - this in turn rotates the crank shaft. The air, which is now its original size, minus the oxygen in it that was burnt during the combustion process is pushed out of the engine by the same piston on is exhaust stroke ... yes, that's right, its not expanding and causing the pressure in the exhaust as you suggest, it is being pushed out by the piston. Engines are air pumps, what goes in, comes out.. it doesn't create mass. It actually consumes it.

and as far as your little pokes, being a certified ASE master tech, doesn't mean you know a damn thing about shift cables, ESA and how they effect ignition systems or drive bellows - I build Chevrolet motors, and until owning this boat, never touched a Ford engine.. and I never told anyone to put an O-ring on a middle plug on any drive...

 

[bruceb58]

Re: OMC Cobra 5.0 overheating

Reinell,

Take a look at this table and compare input cfm to output cfm. I think you might change your opinion:

http://www.asia.donaldson.com/en/exhaust/support/datalibrary/1053747.pdf

you may want a mulligan on this one too:

it doesn't create mass. It actually consumes it.

 

[Reinell-BRXL-191]

Re: OMC Cobra 5.0 overheating

Ok, we are not talking about car or truck motors, we are talking about a boat motor that is having water injected in to it... that water stops all expansion of the air in the exhaust system, I am sorry I wasn't more clear about that... any figures you are using is based on gas continuing to burn in an open exhaust system, there is no fire past the risers in an OMC engine - those figures only work when you have an exhaust temp of 1000 degrees, that heat does expand air - but doesn't create it

Also, standard figures for determining expanded CFM in an exhaust system are based on both manifolds feeding a single exhaust with a set back pressure. Boat engines have very little back pressure, a water cooled exhaust, and each tubes cfm will not exceed the intake cfm - as the reference stated, a 302 can possibly consume 500 and change of air, that figure is divided in to both manifolds at exit, the exhaust is then cooled to well below 200 degrees in order to not harm rubber components. so, when we were originally talking about the air flow in one manifold, I was correct as to it's cfm. That cfm does not exceed the intake cfm.

 

[bruceb58]

Re: OMC Cobra 5.0 overheating

Water and the exhaust don't mix until the exit of the riser.

Trust me, the exhaust at that point is VERY hot. That is why the rubber at the exit of the riserwill melt very quickly without water. The exhaust temp as it enters the manifolds is going to be close to 1400? on a gas powered engine as it enters the manifold which is why the manifold is sized sufficiently to handle the massive expansion of the exhaust gas. The water jacket's purpose is not to cool the exhaust gas in the manifold...it can't. Its purpose is to insulate the heat from the engine compartment as required by USCG regulations.

 

[Idlespeedonly]

Re: OMC Cobra 5.0 overheating

Really?
"You are being given 2 different sizes, because you need both.. the upper fill plug requires the O-ring - the lower drain plug requires the washer.."
I never said gas continues to burn in the manifold.

Think of combustion like a bullet. Pull the trigger primer (spark plug) ignites the powder (gas) it goes bang. Bullet goes out the other end with up to 50000 psi pushing it out. Where in the world did all that air come from? That is right. combustion!
Same EXACT thing that happens in an engine.
Again the only time the exhaust is mixed with water is at the end of the riser, not before like you are suggesting. Do what Bruce said, show us a video.

 

[Reinell-BRXL-191]

Re: OMC Cobra 5.0 overheating

Really?
"You are being given 2 different sizes, because you need both.. the upper fill plug requires the O-ring - the lower drain plug requires the washer.."

And, what I said is completely true.. the O-ring goes on the upper unit fill plug, and the washer goes on the lower unit drain plug.. Matter of fact, because I was wondering if I gave wrong advise.. I just went out and unscrewed both plugs.. and yep... I am right, my bad for calling the dipstick hole a fill hole

 

[Idlespeedonly]

Re: OMC Cobra 5.0 overheating

The upper where the dipstick is is not for filling, it does get an oring. Only the middle one is. Never fill from the top. The middle gets the plastic along with the lower one also.

Check this link out. It iv very good.

http://www.grc.nasa.gov/WWW/k-12/airplane/engopt.html

But then again, what do rocket scientists know anyhow.

 

[bruceb58]

Re: OMC Cobra 5.0 overheating

And, what I said is completely true.. the O-ring goes on the upper unit fill plug, and the washer goes on the lower unit drain plug.. Matter of fact, because I was wondering if I gave wrong advise.. I just went out and unscrewed both plugs.. and yep... I am right, my bad for calling the dipstick hole a fill hole

There is no upper unit fill plug. The fill plug is in the lower unit. The o-ring goes on the dipstick plug. The drain plug and the fill plug both use the same part which are called washers by OMC.

If you have an o-ring on your fill plug, you are going to leak.

The fill plug and the drain plug both use the same washer. You also need to replace the o-ring on the dipstick.

Item #54 is the washer and is used in the 2 places mentioned
http://www.marineengine.com/parts/o...ion=Lower+Gearcase+-+Standard+(r.h.)+Rotation

#9 is the o-ring
http://www.marineengine.com/parts/o...er=OMC+Stern+Drive&section=Upper+Gear+Housing

 

[Reinell-BRXL-191]

Re: OMC Cobra 5.0 overheating

There is no upper unit fill plug. The fill plug is in the lower unit. The o-ring goes on the dipstick plug. The drain plug and the fill plug both use washers.

If you have an o-ring on your fill plug, you are going to leak.

did you not just read what I wrote? I said " my bad for calling the dipstick hole a fill hole"

The guy was being told 2 different part numbers, one was a o-ring, one was a washer... I told him that both are used on the drive.. the o-ring goes on the upper , the washer on the lower, it was my mistake to have said fill hole on the dipstick hole..

And since I said it was my bad, you decided to come in and try and teach me? nice....

 

[Ck111484]

Re: OMC Cobra 5.0 overheating

It looks great! My body is having problems keeping up with my ambitions.

Was it badly faded before you started?

I hear you, a boat is a lot of surface area!
Ehh, my boat was what I would consider "rough" when I got it (though the folks in, say, the restoration forum would probably disagree). Chalky exterior, faded/chipped pinstripes, dirty in and out, generally "unloved".
This picture makes it look a lot better than it was:

And now:

Can't say enough good about 3M products; they really make good on their claims.
(Please disregard the trailer, haven't even had a chance to work on it yet)

 

[bruceb58]

Re: OMC Cobra 5.0 overheating

Glad you didn't go the lazy vaseline way. Do a search on these forums for vaseline. You would be amazed.

 

[Ck111484]

Re: OMC Cobra 5.0 overheating

Glad you didn't go the lazy vaseline way. Do a search on these forums for vaseline. You would be amazed.

Just read about it... that is just... :facepalm:

 

[HT32BSX115]

Re: OMC Cobra 5.0 overheating

Glad you didn't go the lazy vaseline way. Do a search on these forums for vaseline. You would be amazed.

I'm am just NOT going to ask!!

 

[Ck111484]

Re: OMC Cobra 5.0 overheating

So my ESA is engaging when shifting into gear, which we all know it shouldn't be, and it ends up stalling the engine... just replaced the lower shift cable, everything seems to be adjusted properly and the control box seems to shift freely. Any ideas? What's the most common reason for the ESA to engage when shifting into gear? Should I replace the cable from the control box to the engine?

Reverted back to Mercruiser wiring for now, which works fine but I'd prefer to have the ESA working properly.

 

[bruceb58]

Re: OMC Cobra 5.0 overheating

Should I replace the cable from the control box to the engine?

That won't help.

Its possible the springs are weak. I somewhat recall the stiffness of those springs were changed at some point but I am pretty positive it was way before 1993.

How long ago for the cable change? You store your drive in the down position?

 

[Ck111484]

Re: OMC Cobra 5.0 overheating

Which springs do you mean?

I actually accidentally ordered a new switch, and I was thinking about swapping the new one in to see if maybe it had a little more tension in it and wouldn't activate going into gear (I really don't see why it is in the first place, it shifts quite easily).

I changed the lower cable myself about a month ago (I was very careful about the measurements).
I always store the boat with the drive up; is that okay?

 

[bruceb58]

Re: OMC Cobra 5.0 overheating

You should store it down always. Main thing is the bellows but for another reason is the cable. I always saw the the cable would get a "set" in it so that when you lowered it, it would bind more.

I am not talking about the shift switch spring. I am talkng about the spring that holds the "W" looking cam that hits the switch.

If its shifting ok, I would be happy with it as long as the ESA isnt causing the engine to quit on the shift into gear.