97 Mariah Z222 Shabah Overheating???
 

First off, I haven't torn into the problem yet...

Out on the lake, boat ran fine all day until going back to docks. This was the only time that day I went WOT when I got an audible alarm---> temperature gauge was around 250F. Was hearing gurgling noise from the thermostat housing. So I fired boat back up and drove at a no wake speed without a reduction in temperature. At the time, there didn't appear to be water in oil and had no issues with cranking or driving.
I am looking for help to pinpoint issue/opinion without having to completely tear into everything. The water impeller was replaced approx. 5-7hours of use ago.

Could it be the thermostat, engine circulating pump, or defective water pump/impeller? Curious as to why the gurgling noise from what appeared to be from thermostat housing/ front of boat?

97 Shabah Z222
5.7L carburetor Mercruiser
Alpha gen2 outdrive
Approx. 555hrs

Thanks for quick responses!

Re: 97 Mariah Z222 Shabah Overheating???
 

Thermostat blockage or failure or cooling system blockage would be my first thoughts if you recently replaced the impeller.

Re: 97 Mariah Z222 Shabah Overheating???
 

I'm really hoping it's just the thermostat...I guess I can pull it and check to see if it's bad...it would be the easiest to replace, without having to break open the stern drive to inspect impeller, although I probably should just to be safe.

Re: 97 Mariah Z222 Shabah Overheating???
 

Is the boat in the water or on a trailer? If in the water you can try pulling the hose from the outdrive to the thermostat housing and run the engine. If you get a geyser from the hose then you know the pump/impeller is ok. When the old impeller was changed were there pieces missing from it? If so then they may be stuck in a cooling passage.


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Re: 97 Mariah Z222 Shabah Overheating???
 

Good thought, I'll check the schematics to know which hose to pull and try. Even though it will only be running for mere seconds, I hate to get the bilge filled with any water...maybe I'll use a bucket to attempt to catch the geyser!

When I did replace the impeller 3 yrs ago and not many hours ago, it was fine and in good shape with no broken pieces.

Re: 97 Mariah Z222 Shabah Overheating???
 

Actually that might be your issue, 3 years and very little use since then may have caused the new impeller to go a bit brittle and break up. Normal change period is every 3-5 yrs on an impeller.

Re: 97 Mariah Z222 Shabah Overheating???
 

Just for my education... I thought the 5.7 had water pumps on the engine? Is there also a water intake impeller in the stern drive? Last year I had 2 separate episodes of overheating during the boating season but they immediately went away (within 2-3 minutes) and I could not figure out what happened.

Re: 97 Mariah Z222 Shabah Overheating???
 

The gurgling sound from the thermostat was water boiling at 250 degrees

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Re: 97 Mariah Z222 Shabah Overheating???
 

I bet bad impeller as mikey t suggests. You can.see.the impeller start sucking water on the muffs. The leakage around thebmuffsbwill very briefly stop as it sucks water and fills the lines.to the water pump. Then shortly after that you should see it flowing from the outdrive exhaust ports and the property when revved.

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Re: 97 Mariah Z222 Shabah Overheating???
 

One thing I did notice is that the engine temp gauge when overheating barely went over 250 degrees F. Is anyone familiar with the max. range that the engine temp gauge goes too? If the gauge is capable of going higher...this leads me to believe that maybe the thermostat was partially stuck. If the gauge only goes to 250, then it could possibly be either the thermostat or the impeller.

Engine/Water Temp Gauge Range???
 

I'm curious if anyone knows the max range of the engine/water temp gauge is on a 1997 Mariah Shabah Z222. My boat overheated just barely above 250 degrees. If the gauge is capable of reading higher, this leads me to believe I have a bad thermostat because it may be sticking. I really hope it isn't the impeller in the drive!

Re: 97 Mariah Z222 Shabah Overheating???
 

250 Deg is way hot!
Normal is 160-180 deg max.
Most gauges max out on reading at 250 deg , so you could in theory be way hotter than that.

Re: 97 Mariah Z222 Shabah Overheating???
 

Water boils at 212f so if you are at 250f then that will certainly explain the gurgling sound you heard. I really dont think its a stuck thermostat and i do think its an impeller issue or even possibly corrosion in your exhaust manifolds.

Re: 97 Mariah Z222 Shabah Overheating???
 

water may boil at 212 DegF but under pressure it will increase the boiling point. So if your thermostat fails to open at the correct temperature you can have a boiling point of >250 degF dependent on the pressure.

Take a look at your thermostat to ensure it is the correct sizing or just replace it.

Re: 97 Mariah Z222 Shabah Overheating???
 

UPDATE.....

Took lower unit apart, impeller is in great condition, no signs of abnormal wear...Will update on thermostat in a bit.

Re: 97 Mariah Z222 Shabah Overheating???
 

Interesting find just now...the impeller blades were fine but it appears as if the plastic bushing in which the key locks into has gotten bigger, hence the key would spin around the inside of the bushing and not lock into the grove within the bushing allowing the impeller to spin!

Crap piece o junk, probably made in China!

Re: 97 Mariah Z222 Shabah Overheating???
 

Good find!:wink_thumbup:
Can you post a pic?

Re: 97 Mariah Z222 Shabah Overheating???
 

Well just got it all back together with another impeller. I did place them on top of each other and there a noticeable difference in the inner diameter of the bushing. I rotated by hand to make sure that it was the issue. Bout to lube it back up and fire it up on the muffs.

Re: 97 Mariah Z222 Shabah Overheating???
 

What a time you have had. I can only hope it works this time.


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Re: 97 Mariah Z222 Shabah Overheating???
 

UPDATE round 2

So the impeller I put on was an old impeller but in good shape. I tested to make sure it would spin by turning the shaft by hand. Hooked up the muffs, turned on water, fired her up. Running fine, have water exiting the exhaust, as it should. Watched temp gauge come to 175 (normal as it has been) and drop...this is showing me the thermostat was opening. Watched tstat start creeping past 175 and slowly kept on going....looked out back and guess what, no water exiting exhaust. I can't imagine on older impeller, that was completely fine when I replaced, has gone bad too.
I wouldn't think exhaust is plugged up because water was coming out.
My only guess is the older impeller just went bad all of a sudden.

Weird and at a minor loss until I order a new impeller kit and try again!

Re: 97 Mariah Z222 Shabah Overheating???
 

Seeng that there is no radiator and radiator cap once the thermostat opens I can't see it being a closed or pressurized system at that point

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Re: 97 Mariah Z222 Shabah Overheating???
 

I'll be picking up a brand new impeller pump kit and installing tomorrow, will let y'all know the outcome.

Re: 97 Mariah Z222 Shabah Overheating???
 

Final Update....

I did a complete water pump impeller service, seals, housing, plate, impeller, and that seemed to fix my overheating problem. Also replaced the impeller key and I could definitely see signs of wear on the old key. I almost immediately had water coming from exhaust and alot! Whereas it took longer to get water out and not near as much exiting. I figured this was my problem but always good to reach out to fellow boaters for advice, this keeps repair cost to a minimum as I can fix almost anything!

Thanks gang!

Re: 97 Mariah Z222 Shabah Overheating???
 

Nice job! :wink_thumbup:

Re: 97 Mariah Z222 Shabah Overheating???
 

Awesome news! Good job!

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Re: 97 Mariah Z222 Shabah Overheating???
 

Great news!


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Re: 97 Mariah Z222 Shabah Overheating???
 

I had mine overheat. The alarm went off and when I opened up the hatch I head the same gurgling noise you are talking about. As mentioned above it was the sound of water boiling. As I continued to listen I then heard a "swoosh." It sounded like when you unclog a drain and the water rushes down the pipe. That was actually the sound of my exhaust flaps melting because of the boiling water. When they did all that water flushed out the back. This caused my motor to hydro-lock (because I tried to start it after the exhaust manifold flaps had melted) and I got water in my sparkplugs. Not a fun day. Pulled the waterpump and the impeller had shredded. Back flushed everything to get the pieces of impeller out and replaced the plugs. Fired up and all was back to normal. Not going to be the thermostat. Safe bet it is the impeller.

Re: 97 Mariah Z222 Shabah Overheating???
 

All this talk makes me want to go change my impeller just for the sake of changing it again lol

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