High engine temperature

[svnfightsvn]

If it runs at normal operating temp when the tstat is out but not when it's in, maybe the new one you put in is defective or doesn't fit properly. You sure your '94 shouldn't run a 160 degree tstat?

Edited October 10, 2017 by svnfightsvn

[Michigan boarder]

What do the plugs look like, are you running really lean?

[Mac5]

 

1 hour ago, Michigan boarder said:

What do the plugs look like, are you running really lean?

Michigan Border- I'm not familiar with either of your questions. Can you explain further? 

 

1 hour ago, svnfightsvn said:

If it runs at normal operating temp when the tstat is out but not when it's in, maybe the new one you put in is defective or doesn't fit properly. You sure your '94 shouldn't run a 160 degree tstat?

svnfightsvn- I've tried two new T-stats. One at 140 and one at 160.  The one in now is 160. The original was also a 160. I also tested the new ones in a pot of hot water and they worked correctly.  

[Michigan boarder]

21 minutes ago, Mac5 said:

 

Michigan Border- I'm not familiar with either of your questions. Can you explain further? 

 

You mentioned a carburetor change, if the carb is tuned to run too lean (not enough fuel) I think that can cause it to run hot.  If you remove a spark plug and they are white, it is running lean.

I pulled my plugs last year, put up some pictures of them and got some great advice from everyone here.

[Mac5]

13 hours ago, Michigan boarder said:

You mentioned a carburetor change, if the carb is tuned to run too lean (not enough fuel) I think that can cause it to run hot.  If you remove a spark plug and they are white, it is running lean.

I pulled my plugs last year, put up some pictures of them and got some great advice from everyone here.

Awesome! Thank you for the insight!!! would you mind telling me where the spark plugs are? Are they in the carburetor? 

[Michigan boarder]

8 minutes ago, Mac5 said:

Awesome! Thank you for the insight!!! would you mind telling me where the spark plugs are? Are they in the carburetor? 

Are you being serious?

[Mac5]

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Edited October 11, 2017 by Mac5
duplicate

[Woodski]

@Mac5:  From your posts it sounds like you are inexperienced with engine work or diagnosing problems.  If you plan on doing your own work, I suggest a couple of paths, get as much proper literature on engines, spend some time reading your owners manual and engine manual and do some quality learning time (internet forums are not a deep learning tool) and second, find a competent mechanically inclined person to face to face walk you through the details on the engine.  Given your inexperience, it will be nearly impossible to blindly diagnose you overheating issue

Your boat was originally equipped with a 140 degree thermostat.  Today, the industry has moved to higher rated thermostats, the 160 was a replacement at some point.

[Mac5]

57 minutes ago, Woodski said:

@Mac5:  From your posts it sounds like you are inexperienced with engine work or diagnosing problems.  If you plan on doing your own work, I suggest a couple of paths, get as much proper literature on engines, spend some time reading your owners manual and engine manual and do some quality learning time (internet forums are not a deep learning tool) and second, find a competent mechanically inclined person to face to face walk you through the details on the engine.  Given your inexperience, it will be nearly impossible to blindly diagnose you overheating issue

Your boat was originally equipped with a 140 degree thermostat.  Today, the industry has moved to higher rated thermostats, the 160 was a replacement at some point.

Thanks for the advice. 

[Bozboat]

44 minutes ago, Mac5 said:

Thanks for the advice. 

Look for a Clymers Engine Manual on Amazon.    Someone suggested I read that book when I first got my boat.  I found it very helpful.  

[boardjnky4]

I'm still betting it's the circulation pump. More than likely, you're getting lucky that the raw water pump is circulating enough water to keep the engine cool without a thermostat, but once you put a thermostat in, you're not getting enough pressure to push water past it, even when it's open.

I would 100% take off the recirc pump and at least visually inspect it.

[Mac5]

1 hour ago, Bozboat said:

Look for a Clymers Engine Manual on Amazon.    Someone suggested I read that book when I first got my boat.  I found it very helpful.  

Perfect! I'll check it out. 

 

22 minutes ago, boardjnky4 said:

I'm still betting it's the circulation pump. More than likely, you're getting lucky that the raw water pump is circulating enough water to keep the engine cool without a thermostat, but once you put a thermostat in, you're not getting enough pressure to push water past it, even when it's open.

I would 100% take off the recirc pump and at least visually inspect it.

Ok, I'll try that again.  That was one of the first things I checked.  

[Mac5]

19 hours ago, Michigan boarder said:

What do the plugs look like, are you running really lean?

I removed all of the plugs. They appear to be "normal". No white and not super black.  When comparing to images online they seem to fall in the normal or "optimal" category I saw. 

[boardjnky4]

36 minutes ago, Mac5 said:

Perfect! I'll check it out. 

 

Ok, I'll try that again.  That was one of the first things I checked.  

 

I'm not talking about the raw water pump with the impeller. I'm talking about the re-circulation pump on the actual engine. Looks like this. probably has a large pulley and belt on it. You'll have to take the belt and pulley off to remove the pump assembly.

[Bozboat]

49 minutes ago, boardjnky4 said:

 

I'm not talking about the raw water pump with the impeller. I'm talking about the re-circulation pump on the actual engine. Looks like this. probably has a large pulley and belt on it. You'll have to take the belt and pulley off to remove the pump assembly.

Remove it from the engine block, turn it over. On the back is a plate.  Remove the plate and inspect. Mine had a broken bronze impeller so it was toast.  If it had not been toast, I could have put the cover back on and reinstalled the original, but personally, I would just order a new one and replace it so I didn't waste my labor.  A true mechanic would put it back if it was not broken. 

[blk93jeepzj]

11 minutes ago, Bozboat said:

Remove it from the engine block, turn it over. On the back is a plate.  Remove the plate and inspect. Mine had a broken bronze impeller so it was toast.  If it had not been toast, I could have put the cover back on and reinstalled the original, but personally, I would just order a new one and replace it so I didn't waste my labor.  A true mechanic would put it back if it was not broken. 

Like this...

[Woodski]

@boardjnky4:  Are you assuming the raw water pump does not have enough pressure or flow to keep the engine cool, the raw water pump provides plenty of volume and pressure to cool the engine without a circulation pump in the system (if a good impeller and housing).  A broken or damaged impeller in the circulation pump can cause a restriction that would create an overheating situation.

[boardjnky4]

16 minutes ago, Woodski said:

@boardjnky4:  Are you assuming the raw water pump does not have enough pressure or flow to keep the engine cool, the raw water pump provides plenty of volume and pressure to cool the engine without a circulation pump in the system (if a good impeller and housing).  A broken or damaged impeller in the circulation pump can cause a restriction that would create an overheating situation.

Exactly what I think is happening

[Mac5]

2 hours ago, Bozboat said:

Remove it from the engine block, turn it over. On the back is a plate.  Remove the plate and inspect. Mine had a broken bronze impeller so it was toast.  If it had not been toast, I could have put the cover back on and reinstalled the original, but personally, I would just order a new one and replace it so I didn't waste my labor.  A true mechanic would put it back if it was not broken. 

Boz- I took off the re-circ pump and took off the back cover. Looks to be in good condition. 

[Mac5]

Here are some images of my spark plugs and the re-circ pump. 

[MadMan]

I would suggest testing with an old school mechanical temp gauge to verify you don't just have an instrumentation problem.  You can install it temporary, or do something like I did.  I have one of these mounted in the engine compartment for issues like this:

http://www.ebay.com/itm/CP7996-Sunpro-Chrome-2-Inch-Oil-Water-and-Volts-Triple-Mechanical-Gauge-Kit-/132157489590?epid=1617816196&hash=item1ec53341b6:g:ynUAAOxyc2pTXtS6&vxp=mtr

 

[boardjnky4]

Are you sure that all the hoses are routed correctly at the thermostat housing?

Might want to compare with a picture from a known good engine.

could explain why it cools correctly with the thermostat removed.

[Mac5]

10 hours ago, boardjnky4 said:

Are you sure that all the hoses are routed correctly at the thermostat housing?

Might want to compare with a picture from a known good engine.

could explain why it cools correctly with the thermostat removed.

interesting idea. i'll check that today. Anybody have any photos of their 350 mag engine?

[Michigan boarder]

58 minutes ago, Mac5 said:

interesting idea. i'll check that today. Anybody have any photos of their 350 mag engine?

Here's a pic of my old engine when it was all stock:

 

[Woodski]

@Mac5:  One area to check, the thermostat housing - the diverter mechanism that controls the flow to the exhaust manifolds, inside there is a rod / plastic ball / spring device that allows water to be diverted to the exhaust manifolds when the thermostat is closed.  In the above picture it is the two 5/8" hoses top front of the thermostat housing that lead back to the risers.  Typical failure mode is the springs fail thus not allowing the plastic balls to close and seal the diverter path.  By opening up the thermostat you created a lower restriction path which perhaps allowed enough water to flow to provide additional cooling.  Repair parts are available at SkiDim.com.  Note:  the circulation pump issues with the cracked impeller are normally associated with later model engines than your '94.