4.3 still oveheating

[jaybrassmonkey]

Still getting hot on the water or on the hose. Here's what I've done so far.
Checked the thermostat in pot of water- checked ok
Pulled the lower unit to check impeller- ok
Water pipe connected in lower unit- check
Thermostat housing not clogged
Manifolds and risers are new and are not clogged
Y pipe not clogged, water exiting transom, pulled old flappers waiting on new ones.

Going to back flush from thermo housing intake when I get the lower unit back on, and pull the power steering cooler to flush it as well. That's all I know to do. If you have any ideas please help.

 

[jaybrassmonkey]

Power steering cooler clean as a whistle.

 

[Four Winns Fanatic]

You didnt happen to mix up one of the cooling hoses that goes to the exhaust manifold with the cooling hose going to the block .If your setup is like my 2008 5.0 l I have a T Water connection part of the thermostat housing that evenly distributes cooling water to both exhaust jackets , just a thought I did this once when I had replaced thermostat.

 

[Bondo]

Going to back flush from thermo housing intake when I get the lower unit back on,

Ayuh,.... Ya back-flush that with the lower Off, so's any junk can get blown out onto the ground, rather than back as far as the pump,....

Put the muffs on, 'n pull that hose from the t-stat housin',....
Holdin' the hose end straight up, a quick blip of the throttle, oughta shoot water nearly a foot in the air,....

 

[jaybrassmonkey]

Four wins- no the way my hoses are sized and shaped they can really only go on one way.

Bondo-yeah, I realized that, lol. I did try what you said- the water did jump when I revved the motor.

Just can't think of anything else it could be. Could the new temp sender be bad? Could the connection from the gauge to the sender be faulty causing a bad reading? I didn't let the motor run long once the gauge read 190, but the risers were cooler and more balanced than before. Would like to get out on the water but don't want to risk messing up the motor.

 

[jaybrassmonkey]

Okay so I've been reading about cold manifold vs. warm a manifolds. Based on the info I found and the picture of the thermostat housing shown with the info, I have a cold manifold exhaust system, which should use the unrestricted riser gasket. I currently have the restricted riser gasket installed. Could this alone be the whole problem? Restricted flow not allowing water to exit quickly enough?

 

[jopes]

I had a issue with over heating once. Impeller kit was new, Tstat new, new engine, new mani's.

Come to find out the impellet kit was not sealing up and it was sucking in exhaust gas, and well not enough water to keep er cool.

I seen this one day by looking at the white tube behind the engine with a flashlight and the engine running at the dock.

Something else to check out.

 

[jaybrassmonkey]

Not sure about a white tube behind the motot, I don't seem to have one behind mine.I guess I'm going to change the gaskets on the risers and see what that does.

 

[jaybrassmonkey]

So, really was hoping to have an answer. None so far. Ran the boat hot today. Absolutely frustrated at this point. It has got to be an impeller problem. No other answer. Hoping I didn't torch something and ruin the motor. After cooling, it will crank and run smoothly until up tot temp again then I shut it off.

Although, I did hook a hose directly to the intake at the thermostat housing. Still ran hot. But that could be because thermo wouldn't open with cold water runnin on it, right.

 

[JoLin]

With all that you've done and checked, I haven't heard you say you've checked t-stat housing and riser temps with a IR temp 'gun', or if the risers are too hot to hold when the temp gauge shows an overheat condition. Is it really overheating, or just telling you that it is? What temps are you seeing on the gauge?

 

[jaybrassmonkey]

I ran it today, got so hot when I pulled it back to neutral it shut off. Hoping it was in time to prevent damage. Hot to touch all the way around. Funds are very limited right now so no temp gun. I believe the gauge is correct When reading 190-200. Again, praying I haven't done any damage. I have started the motor on the house at home 3 times, just long enough to start, seems to run fine, hoping for the best.

I'm not gonna tell anyone that I think my thermostat was in upside down. But to be fair NO ONE had mentioned that here before, lol!

Now I have an outdrive gear lube leak, and the previous oil leak is back in the motor housing.

 

[gonzalez3346]

I am currently dealing with the same issue. Replaced all components mention and still have the issue. The only difference is that my engine temperatures is correct based on the IR gun. My guess will be the temperature gauge only after checking the temperature with the IR gun.

 

[jaybrassmonkey]

Ok so, impeller is good, water circulation pump is good, all plumbing is good and in correct place.

Last thing I did was run the motor on the hose without the thermostat in it. It ran steady at 130, which I know is low but NOT HOT. All parts warm but not hot. I checked flow through the motor by pulling the drain plugs while running, good warm water coming through.

Put the thermostat back in and it ran hot. Tstat checks good on the stove but will be replacing it for good measure, I guess, and will check it out again.

Anyone have any ideas?

 

[Bt Doctur]

with no stat it should be around 100 , not 130. not enough water flow.Did you replace the base gasket on the pump body?
Did you assemble it correctly? pull the drive and use a hose directly into the housing and report the results,

 

[jaybrassmonkey]

Ok, pulled the drive. Flushed forwards and back, no apparent obstruction between thermostat housing and outdrive. Only other place I cannot say is clear is the foot, between the impeller and the foot intake. Any direction on checking this area?

Are you talking about the impeller base plate and gaskets? I didn't see any other way for them to go on, just matched up the shapes. Could it be possible I have the wrong impeller, too big, not turning fast enough because fins are bent over too far, too much friction?

 

[UncleWillie]

... Could it be possible I have the wrong impeller, too big, not turning fast enough because fins are bent over too far, too much friction?

Highly unlikely you could close it up with an over-sized Impeller. Too small maybe, but it would look really odd!
There is no way the Impeller can slip due to friction.
The impeller will always turn at the same speed as the shaft because they are Keyed together.
The Impeller Key was reinstalled, right???

 

[jaybrassmonkey]

Yes the key is installed. At this point I'm questioning the bottom gasket. It seemed to close up a lot of holes on the base plate. If the impeller turns with the shaft, there has got to be an obstruction in the foot at the intake. I'm afraid to dig into that area though.

 

[NHGuy]

Nope, hold it. It runs hot with water directly to the thermostat. Take off the thermostat housing and root out any bad rust, make sure the check balls can move. Verify your hose routing.
Then if it's still warm check the water circulation pump. Remove the belt and spin it by hand. It should turn smooth without noises or wiggling. If that's still good see if there's junk in any of the hoses.
If there still aren't any answers take off the circ pump and see if you can scrub, blow or rinse out the block at all.

 

[NHGuy]

I forget, does your thermostat housing use the check balls? What year and drive is it? If it's supposed to have them and does not the cold water can keep running past the stat which might then stay closed and cause high temps.

 

[jaybrassmonkey]

Thanks NHGuy, I've done all that. It's a '97 mercruiser, alpha I gen+. Thermos housing is rusty inside but otherwise unobstructed. No check balls on this model. Water circ pump is good as well as all plumbing, hoses, etc.

This thermo housing is like a double T. Water comes in from the stern drive to the housing, one hose to the bottom of each exhaust manifold, one large hose to the circ pump.

I AM STUMPED.