OMC 2.3 Running Hot Need Help

Bulbash · Sep 2, 2013

Guys still have the same issue from a month before. Engine runs slightly hotter than supposed to, according to the gauge around 180* - 190* depending on rpm's. Recent new parts: Impeller with housing and all gaskets (sealed supper well with liquid gasket absolutely no leaks), thermostat, plugs, wires, fuel filter, alternator belt. Timing adjusted to 10* advance as per manual

In general boat runs well no signs of anything abnormal except when after running at high rpms if you turn it off it keeps running for a few seconds, dying out... I think it is a sign of high temperature in the combustion chamber. Also, I had this boat for 2 seasons now and it always was hard to start from cold, needs some throttle in neutral to start, but idles smooth after a warm-up.

I started worrying after melted spark plugs a few weekend ago (was separate thread before). But to be honest I think issue was not resolved.

My dad who is mechanic, tells me to retard timing to 6* instead of recommended 10* and see if that is going to help... I at this point I think it is either timing, or maybe the problem is in a lean mixture which causes elevated temperatures in combustion chamber.

Questions:
1. What are the signs of the lean mixture?
2. Any instructions on how to adjust carburetor? Turning 2 screws until runs good? Doesn't sound very trustful..
3. Setting timing from 10* recommended by the book to 6*, will it likely help my issue?

HT32BSX115 · Sep 4, 2013

Re: OMC 2.3 Running Hot Need Help

Bulbash said:
Guys still have the same issue from a month before. Engine runs slightly hotter than supposed to, according to the gauge around 180* - 190* depending on rpm's.

What T-stat are you running?

Did you switch to a different gage and sender? Maybe it's your gage.....(although run-on is frequently related to running hot)

1. What are the signs of the lean mixture?

Look at your plugs. (the new ones) Are any of them looking burned

2. Any instructions on how to adjust carburetor? Turning 2 screws until runs good? Doesn't sound very trustful..

That's idle mixture. running mixture is controlled by changing jets. Maybe that carb was jetted for high altitude.....

3. Setting timing from 10* recommended by the book to 6*, will it likely help my issue?

If it's not pinging, it's probably not advanced too far BUT............... I seem to remember the OMC service manual indicating to use 8 degrees when using 87 AKI fuel.

What sort of shape is your riser (exhaust elbow) and manifold in? Is it rusty (internally)? If either is (too) rusty, you will not flow sufficient water through the entire system regardless of how good your raw water pump is.....and you'll get over-heats at high power settings.....

Regards,

Rick

Speak · Sep 4, 2013

Re: OMC 2.3 Running Hot Need Help

Well said Rick nice reply. Bullbash - what is your idle speed in neutral and in gear when warmed up ? This is a strange scenario. My 2.3 is set to 10 advance and I run 87 octane with an idle spead of 600+ - 50 rpm and I have no run on. Have you check to see if your exhaust flap is blocking the water flow? Check snd make sure your carb base gasket is not leaking by spraying some brake cleaner around the base of the carb when the engine is running. If its leaking your rpm will jump up. For that matter check your intake gasket too the same way. Maybe the intake manifold is cracked. False air entering the engine will cause a lean run condition. Do you have another carb to try ? One other thing are u sure the impeller is supplying good flow and that your circulating water pump is good. I only ever hit 180deg after 30 min of wot at top speed. Sounds like your engine block just can't purge out that heat. Sorry for the ramble - stu

bonzoscott · Sep 4, 2013

Re: OMC 2.3 Running Hot Need Help

I would like to add - Don't immediately shut your motor off after a hard run. Idle for a bit and let it cool itself. Shutting off immediately has been the blame for dieseling in some cases.

Bulbash · Sep 4, 2013

Re: OMC 2.3 Running Hot Need Help

What sort of shape is your riser (exhaust elbow) and manifold in? Is it rusty (internally)? If either is (too) rusty, you will not flow sufficient water through the entire system regardless of how good your raw water pump is.....and you'll get over-heats at high power settings.....

Checked that it has very little rust and flappers seem to be in a good working shape.

That's idle mixture. running mixture is controlled by changing jets. Maybe that carb was jetted for high altitude.....

Will be trying to readjust tomorrow...

My 2.3 is set to 10 advance and I run 87 octane with an idle spead of 600+ - 50 rpm and I have no run on.

According to the tachometer on the boat it is around 600 to 800rpm very hard to read it...

For that matter check your intake gasket too the same way. Maybe the intake manifold is cracked. False air entering the engine will cause a lean run condition. Do you have another carb to try ?

I do suspect that something causes lean mixture, either bad adjustment, cracked manifold... Is it possible that inline filter is clogged and not letting enough fuel at higher rpms and making system run lean?

I would like to add - Don't immediately shut your motor off after a hard run. Idle for a bit and let it cool itself. Shutting off immediately has been the blame for dieseling in some cases.

I agree with you and usually try to avoid this situations, but still it should not happen.

Bulbash · Sep 6, 2013

Re: OMC 2.3 Running Hot Need Help

Had some time to work on the boat today, replaced an inline fuel filter at the carbs, it did not look too bad, but probably a good to have a new one... Cheked the carb settings, it turned out that two screws have been never adjusted or maybe adjusted, but I found them in a position of screwed all the way in, when adjusted to about 4 - 4.5 turns engine started to run smoother... When screws are all the way in, is it more air or fuel?

Speak · Sep 6, 2013

Re: OMC 2.3 Running Hot Need Help

In is lean and out is rich. Those screws are for idle only. Once off idle the main jets come on line and those screws do nothing. Did you check for air leaks like I mention previously?
Stu

Bulbash · Sep 6, 2013

Re: OMC 2.3 Running Hot Need Help

Speak said:
In is lean and out is rich. Those screws are for idle only. Once off idle the main jets come on line and those screws do nothing. Did you check for air leaks like I mention previously?
Stu

Yes, checked for airleaks... Does not seems to be the case...

Is there a way to check water-pump? Or just replace it? I tried spinning the pulley bearing seems fine...

Bulbash · Sep 6, 2013

Re: OMC 2.3 Running Hot Need Help

Speak said:
In is lean and out is rich. Those screws are for idle only. Once off idle the main jets come on line and those screws do nothing. Did you check for air leaks like I mention previously?
Stu

Are you sure that those settings does not play any role pass the idle...

Speak · Sep 7, 2013

Re: OMC 2.3 Running Hot Need Help

Positive. The carb has main jets inside that control fuel administration.

Bulbash · Sep 7, 2013

Re: OMC 2.3 Running Hot Need Help

Speak said:
Positive. The carb has main jets inside that control fuel administration.

In this case I'm stuck... Not even sure what else can be wrong...:facepalm:

Speak · Sep 7, 2013

Re: OMC 2.3 Running Hot Need Help

It's probaly not running lean. But more likely hot due to a cooling issue. Go back thru your cooling system. Try and back flush the system. Pull the thermostat housing off and double check that new stat u put in, in a pot of boiling water with a thermometer to make sure it's opening at the right temp. Bulbash what color are your plugs at the electrode. Send a picture. Also. Have you tried another temp gage and sender?

Bulbash · Sep 7, 2013

Re: OMC 2.3 Running Hot Need Help

Try and back flush the system.

Did it a few times already system looked clean nothing came out... I didcheck manifold, elbow and flappers all looks good with very minor rust...

Pull the thermostat housing off and double check that new stat u put in, in a pot of boiling water with a thermometer to make sure it's opening at the right temp.

Does it matter which way thermostat goes into the housing? Does it go with spring to the manifold or spring to the housing? I will try to boil it and see how it works..

Bulbash what color are your plugs at the electrode.

Plugs are all black right now, but that is probbly from me screwing with carb settings ...

Have you tried another temp gage and sender?

No I did not... is there a way of checking that gausge? Also, where is the sensor located?

Bulbash · Sep 7, 2013

Re: OMC 2.3 Running Hot Need Help

I was aso thinking, maybe I can get a 140* thermostat instead of 160* so that will help keep things a little cooler... Anybody knows a part number for 140* thermostat from mallory or sierra?

Speak · Sep 8, 2013

Re: OMC 2.3 Running Hot Need Help

It makes a huge difference which way that stat goes onto the housing. The spring is always in the flow of hot water. The sending unit is on the back of the head on the the intake side right next to the oil pressure sender.

Bulbash · Sep 8, 2013

Re: OMC 2.3 Running Hot Need Help

Speak said:
It makes a huge difference which way that stat goes onto the housing. The spring is always in the flow of hot water. The sending unit is on the back of the head on the the intake side right next to the oil pressure sender.

So do the spring side of a thermostat goes in to the manifold or the housing? Mine was installed spring into the housing...

Speak · Sep 8, 2013

Re: OMC 2.3 Running Hot Need Help

Bulbash said:
So do the spring side of a thermostat goes in to the manifold or the housing? Mine was installed spring into the housing...

This is right. The spring needs to be in the hot water which will open purging our the hot water into the manifold.

Do you have access to a thermo gun? If you did you could point it at the sender at the head and tell for sure what the temp of the head is.

Im sure your melted plugs was from the out of adjusted ignition timing. The 2.3 running at 180-190 is normal man, thats where mine runs when i work the pants off it. As long as it does not overheat you good bulbash. Keep an eye on those plugs now and see where the color ends up. I think you are just over sensitive now. I truly believe you are good now that you have adjusted that ignition to spec.

cheers.
Stu

Bulbash · Sep 8, 2013

Re: OMC 2.3 Running Hot Need Help

Speak said:
This is right. The spring needs to be in the hot water which will open purging our the hot water into the manifold.

Do you have access to a thermo gun? If you did you could point it at the sender at the head and tell for sure what the temp of the head is.

Im sure your melted plugs was from the out of adjusted ignition timing. The 2.3 running at 180-190 is normal man, thats where mine runs when i work the pants off it. As long as it does not overheat you good bulbash. Keep an eye on those plugs now and see where the color ends up. I think you are just over sensitive now. I truly believe you are good now that you have adjusted that ignition to spec.

cheers.
Stu

Thanks for help I will get temp gun at work and next time I'm on the lake I'll see how it goes...

HT32BSX115 · Sep 8, 2013

Re: OMC 2.3 Running Hot Need Help

Bulbash said:
I was aso thinking, maybe I can get a 140* thermostat instead of 160* so that will help keep things a little cooler... Anybody knows a part number for 140* thermostat from mallory or sierra?

A 160 stat is what you want.

180 is not too hot either. If your gage is not right, it could be the actual gage or the sender (or both)

Bulbash · Sep 9, 2013

Re: OMC 2.3 Running Hot Need Help

A 160 stat is what you want.

180 is not too hot either. If your gage is not right, it could be the actual gage or the sender (or both)

I actually got a 140* thermostat today... Want to try it out... Only $12 anyways...

OMC 2.3 Running Hot Need Help

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