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HELP 95 Sunsetter Overheated late yesterday


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Guys and gals, we were out yesterday afternoon and all was well while I was driving. A young boy (5yr) wanted to try and ski, so his dad drove boat and I helped little guy get started. After he was done I went up to start the boat and temp guage was up around 180-190, usually around 130-140. Engine buzzer was going off when I turned ignition on. Opened hatch to let engine cool. Once the engine was cool, started and headed to ramp, temp started coming up fast. It got to about 170 and I was about to shut it down and then it just dropped to typical 130-40. Dropped off person to back down trailer. While idleing in the water waitingfor trailer, the temp started to climb again, it got to 160 and I just shut it off and swam boat to the trailer.

Need to order parts and have this problem resolved by Thursday evening when we leave for holliday weekend. So what would you all order? I have a spare impellar. I was thinking the problem was sticking thermostat. So I plan on ordering one of those and another impellar. Not sure if I should order anything else. Need you alls expertise..... Thanks in advance.

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It is actually quite rare for a thermostat to stick, but cheap and simple to change but your description of the temp dropping back supports that theory as a possibility. You can get replacements from a local auto parts store, if you can't actually find a marine version quickly, an automotive one will work but you need to drill a couple of bleed holes in it prior to intalling.

The most common overheating causes are impeller failure and water intake blockage, your description also supports these as causes. Check the impeller, check the intake water hoses and the transmission cooler inlet side for debris. If you have a weed strainer, check that for accumulated debris.

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It is actually quite rare for a thermostat to stick, but cheap and simple to change but your description of the temp dropping back supports that theory as a possibility. You can get replacements from a local auto parts store, if you can't actually find a marine version quickly, an automotive one will work but you need to drill a couple of bleed holes in it prior to intalling.

The most common overheating causes are impeller failure and water intake blockage, your description also supports these as causes. Check the impeller, check the intake water hoses and the transmission cooler inlet side for debris. If you have a weed strainer, check that for accumulated debris.

Thanks for the quick reply, yes I would have thought that a themostat sticking is unlikely also, but cheap. By chance do you know what part # the auto version would be, motor is 350 Magnum. My parts guys can't really help over the phone and I didn't have enough time last night to take the old one out. If I can find an auto one that will work what size holes and where will they need to be drilled.

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Actually, any small block Chevy t-stat will work. You can get them in many temp ranges, 140 deg F for typical marine, 160, 170, 195 deg F are also available. The marine ones are stainless or brass so corrosion is not an issue, a standard automotive one will eventually corrode due to no antifreeze in the system.

You basically need to drill a couple of 1/8 or 3/16" dia. holes in the outer ring, you are basically ensuring that there is a bleed hole so that some water flows through the entire system and allows the raw water pump to keep pumping and the exhaust to always have some cooling water in it.

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Like Woodski said "a thermostat failure is rare". Go after the impeller and back flush the transmission. Once you change the impeller be sure the gasket is on the cover. Once your on the water or hook up to water look for water leaks at the back of the impeller housing and gasket. A small drip from the rear is OK, but anything more will delay priming the impeller and quickly cause a failure. Your bu is older so it may be time for a new impeller rear seal or easier just to buy a complete unit.

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Actually, any small block Chevy t-stat will work. You can get them in many temp ranges, 140 deg F for typical marine, 160, 170, 195 deg F are also available. The marine ones are stainless or brass so corrosion is not an issue, a standard automotive one will eventually corrode due to no antifreeze in the system.

You basically need to drill a couple of 1/8 or 3/16" dia. holes in the outer ring, you are basically ensuring that there is a bleed hole so that some water flows through the entire system and allows the raw water pump to keep pumping and the exhaust to always have some cooling water in it.

These holes you speak of on the outer ring, drill them any distance from the outer edge or is there a distance I need to try and achieve. Thanks again.

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Like Woodski said "a thermostat failure is rare". Go after the impeller and back flush the transmission. Once you change the impeller be sure the gasket is on the cover. Once your on the water or hook up to water look for water leaks at the back of the impeller housing and gasket. A small drip from the rear is OK, but anything more will delay priming the impeller and quickly cause a failure. Your bu is older so it may be time for a new impeller rear seal or easier just to buy a complete unit.

I agree that thermostat sticking is rare, but the temp came up and then dropped. I wouldn't think that if the impeller had failed wouldn't circulation cease completly. thanks I just want it fixed by the weekend.

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I am looking @ Ski Dim and trying to figure out which impeller I should order to replace the spare that I am going to install. This is the first year for the new boat and I am not for sure which one this boat uses, can't seem to get them on the phone and would like to order quickly to ensure delivery before weekend. I need a part # someone PLEASE... thanks in advance.

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An impeller can partially fail and produce that type of scenario. Blockage can do the same thing. Correct on the holes in the t-stat, you just have to make sure it bleeds water from one side to the other, centered in the ring works just fine.

SkiDim usually answers the phone and they are very knowledgeable, a dealer can help identify which unit. You need to provide the marinizer (Indmar, PCM, Mercruiser) and maybe type of pump (side mount or crank mount). The dealer will probably know just from the boat model itself.

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An impeller can partially fail and produce that type of scenario. Blockage can do the same thing. Correct on the holes in the t-stat, you just have to make sure it bleeds water from one side to the other, centered in the ring works just fine.

SkiDim usually answers the phone and they are very knowledgeable, a dealer can help identify which unit. You need to provide the marinizer (Indmar, PCM, Mercruiser) and maybe type of pump (side mount or crank mount). The dealer will probably know just from the boat model itself.

They answered the phone and got me a thermo and impeller on 2 day guarantee Wed. delivery. I will take it apart this evening and be waiting on parts. Thanks for the help and I hope these two items get me on the water for the 4th weekend. Hope all your fireworks are awesome.

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run it without a thermostat to make sure it doesn't still heat up. don't wait.

Don't wait till Wednesday you mean. Good idea, I can take it out this evening after I check for obstructions in cooling lines and pull the thermo out and hit the water.

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Ok, I have the top plate off and the top gasket off. NOW WHAT??? My Nautique was simple looking compared to this. How do I get thermostat out? I searched a second ago and found a diagram, but now I can not find it. I just don't want to tear anything up. Please lend helpin hand.

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UPDATE!! I had the top plate off and was waiting for guidance on housing/thermostat removal. I then took impeller out and it looked great. No weather cracking or pieces missing. I will go ahead and replace @ time of install. I then took the line off @ the tranny cooler and whoaaaa to my amazement there was a large ball of rubber impeller lodged in the cooler inlet. I had never had this line off so my amazement is that I ran it like this for the last summer and a half with NO PROBLEMS. Now all of a sudden we have blockage. I cleaned all impeller debris out and installed line. Then I removed the thermostat housing and tapped the thermostat and pvc insert out from the bottom. (Figured this out after looking at it longer) Any hows since its all apart I am going to replace gaskets, impeller, and themostat and hopefully have a troublefree Independence Day weekend.

Edited by scout1ton
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UPDATE!! I had the top plate off and was waiting for guidance on housing/thermostat removal. I then took impeller out and it looked great. No weather cracking or pieces missing. I will go ahead and replace @ time of install. I then took the line off @ the tranny cooler and whoaaaa to my amazement there was a large ball of rubber impeller lodged in the cooler inlet. I had never had this line off so my amazement is that I ran it like this for the last summer and a half with NO PROBLEMS. Now all of a sudden we have blockage. I cleaned all impeller debris out and installed line. Then I remove the thermostat housing and tapped the housing and pvc insert out from the bottom. (Figured this out after looking at it longer) Any hows since its all apart I am going to replace gaskets, impeller, and themostat and hopefully have a troublefree Independence Day weekend.

I had the same problem on my old Echelon. Had a new impeller in it, but was running too hot. The tranny cooler screen was full of chunks of rubber from an old impeller that let go. The shop vac took care of that debris easily and I was back in biz!

-- Mike

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I had the same problem on my old Echelon. Had a new impeller in it, but was running too hot. The tranny cooler screen was full of chunks of rubber from an old impeller that let go. The shop vac took care of that debris easily and I was back in biz!

-- Mike

New thermostat, new impeller, and debris cleared from the cooler screen. I took the boat out last night after installing new parts and no overheating, no leaks and a steady 140* temperature. Thanks to SKI DIM for rushing the parts and for all you alls thoughts and advise. Looks like it will be a great weekend.

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