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I have a 1993 Malibu Sunsetter. It has the 350. When I

I have a 1993 Malibu...
I have a 1993 Malibu Sunsetter. It has the 350. When I bought it a couple years ago, the temp gauge never came up from zero. It always ran fine but I read some stuff that said the temp should be higher and decided to change the thermostat. I changed to a 160* thermostat from the 140*. Then it started to over heat. I thought it was the thermostat so I removed it and ran without it. I assumed it would run very cool now. It still overheated. So I checked the impeller, it was fine and so was the housing. Then I checked the flow from it by disconnecting the hose. It had, what I thought was, good volume and pushed water through hard even after I pinched off the hose.
One thing I'm not certain of is the wires to the two temp sensors just over the thermostat. I might not have the wires on the correct sensor.
Thinking it might be a problem by not having any thermostat, I put in a new 140* thermostat and there is no difference. It over heated again. Then I tried switching the wires on the temp sensors over the thermostat because I was never sure I had them right. Of course the temp gauge went down because it was disconnected but when it was connected a few seconds later the temp started going down. I confirmed that by feeling the hoses and they were warm but not burning as they were before. I don't understand why the temp changed. When I tried to duplicate it, I couldn't and it began to over heat again.I'm stuck. Is there any electrical control regulating the temp some where or is it only the thermostat? Do those sensors over thermostat do anything other than give gauge readings? What am I missing?Thank you!
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Answered in 3 minutes by:
8/19/2017
Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 17,876
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
Verified

H​ello my name is ***** ***** am I speaking with? I read what you wrote. Is the engine actually overheating, did you verify the temperatures by checking the engine with an IR temp gun, or are you relying on the gauge in the boat? Can I also get the serial number on the engine please.

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Customer reply replied 11 months ago
I could hear the water boiling and the hoses were burning hot and the gauge. Engine 0D840807

Okay got it. How are you running the engine, are you running it on a garden hose or is the boat in the water?

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Customer reply replied 11 months ago
On lake.

Got it. Are you near the boat now for a test?

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Customer reply replied 11 months ago
No I can get there in 15 minutes. Will I need tools?

J​ust a screwdriver and a bucket. All I want you to do is pull the output hose off the seawater pump. Start the engine up. Bring the RPMS up to 1000. Once the water starts flowing aim that hose into the bucket. Count to exactly 10. Then aim the hose away and shut the engine off. Do this and let me know if you get more than a gallon of water in the bucked or less than a gallon of water.

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Customer reply replied 11 months ago
ok

Okay let me know what you find.

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Customer reply replied 11 months ago
I'm sorry I missed you asking. I'm Paul.Exactly one gallon

Hi Paul. Okay that is to low, you should have had 2 gallons minimum. When was the last time that impeller was replaced with a new one?

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Customer reply replied 11 months ago
I've checked it. It's perfect and the inside of the housing is perfectly smooth.
Customer reply replied 11 months ago
Belt is tight too.

Hi Paul. Okay that is to low, you should have had 2 gallons minimum. When was the last time that impeller was replaced with a new one?

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Customer reply replied 11 months ago
A month ago.
Customer reply replied 11 months ago
Taking it apart now

The impeller was new 1 month ago?

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Customer reply replied 11 months ago
I've used one tank of gas.

Right now there is not enough water out of the pump, it should be double what you are getting. You will want to check the water inlet on the boat and make sure that is not clogged. If there is a power steering cooler on the seawater pump inlet hose that will need to be checked for clogs. When the engine runs, the seawater pump makes a vacuum and sucks water up from the lake. What can also happen when the hoses get old is the hoses can simply collapse under that vacuum, so that will need to be checked as well. If that all looks good then there is a problem with the impeller or the pump itself is no good and has excessive wear inside of it. Does that all make sense. Also, this engine does call for a 140 degree thermostat, so you will want to use that one. I do want to make sure you are happy with my service before you go. If you had a further question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.

Please note that our question sessions never close out, so if you need to come back later down the road with follow up questions to the issue, you can do so at any time, even after putting through a rating.

Thanks in advance, and good luck
Jason

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Customer reply replied 11 months ago
I have the impeller apart now. It and the inside of the housing are perfect. The intake hose is firm and hasn't collapsed. I'll check it for vacuum leaks but I've been confident it was good. Tell me about the inlet. Is there any thing more to it than what I see when it's out of the water. Does it have a filter somewhere?

On most of them there isn't any kind of strainer/filter, but you would have to take a look as every boat builder is different.

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Customer reply replied 11 months ago
Found a pin hole in the intake pipe.

That would do it. When the engine runs the water plumbing is under a vacuum. What happens is the seawater pump will suck air in through that leak instead of sucking water up from the lake. Does that make sense.

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It looks you read my answer and left without selecting a rating for my service, replying back, or simply thanking me. Was there something else?

Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 17,876
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
Verified
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Customer reply replied 11 months ago
It turns out that that wasn't the issue. The transmission cooler was plugged with chunks of old impeller rubber on the intake side. I pulled it all out and it's fine. Even with the new sea water hose I was only getting about a gallon out of the impeller pump when I counted to 10. Thanks for being there.
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