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JonnyRad91

Strange Overheating Problem

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JonnyRad91

So I am having a weird overheating problem.

Start boat, comes up to temperature just fine. I can run it fast and hard and it stays around 160-165 without issue. Once I come back down to idle it stays normal for about 30 seconds and then it starts to rise. It slowly gets up around 190, stays there and comes back down to 160. The whole thing lasts about 3 minutes. If I take off again while it is hot the temp will come back down. If I wait for it to come back down to normal operating temperature and I take back off again, the temp falls to about 120-130.

I replaced the impeller

I replaced the thermostat

I checked all those hoses, looked for any blockage, emptied my sea strainer and blew out the through haul under the boat from the transmission hose.

I mean typically if you temp goes down as you rev up its a sign of a bad impeller. But the impeller is brand new and my temp goes down on its own if I just wait long enough. I figured it was the thermostat was not opening but thats now been replaced and if it was sucking air, I would not think the problem would magically correct itself.

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edwin

I'm guessing you have a blockage somewhere, most likely in the trans cooler screen

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JonnyRad91

I took the hose off to the oil cooler and there was nothing in the screen. I also have a sea strainer before that which is clean. I took the hose off to the transmission and there was nothing in there.

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REW

Have you checked the cooling system for leaks while the temp is up or coming down? Sounds like you have verified the normal items are good.

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JasonK

On my motor there could sometimes be pieces in the hose between the impeller housing and the trans cooler. They need to be flushed out or the hose taken off and emptied. Could yours be like that? Not sure about the v-drives.

I know you took the HOSE off to the oil cooler, but did you flush it?

WHERE THE HOSE AT? :)

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AndyP

Do you have a heater? I had problems with mine causing overheating. I bypassed the whole thing and the problem went away.

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oceanbu

Not much help here but friend of mine is having the a similar problem except boat won't prime when you first put it in the water unless you put in gear and get on plane then good for rest of day. He's replaced impeller, impeller pump, water pump, hose (found a pin prick in it so thought it was sucking air), thermostat but still having problem.

BTW love your boat. Looks sweet!

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tvano

SEa strainer sucking air?

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FastFreddy

Not much help here but friend of mine is having the a similar problem except boat won't prime when you first put it in the water unless you put in gear and get on plane then good for rest of day. He's replaced impeller, impeller pump, water pump, hose (found a pin prick in it so thought it was sucking air), thermostat but still having problem.

BTW love your boat. Looks sweet!

Instead of doing this he can just dip it in the water, put it in neutral and rev the engine to 3000 rpm. This will prime it for the day :)

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BlackBluMalibu

sounds like engine driven water pump may have slight air/seal leak. does the bilge stay dry when in storage or do you have a litlle water which could be the seal at engine driven water pump? Could also be getting air in system from multiple sources including heater, if you have a heater system.

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malibucat

Temperate rise at idle, it is sucking air somewhere. Temperature rise running hard , it has a blockage someplace. Check all your lines, check thermostat housing, tranny cooler.

Lastly after swearing you checked every place it could be,take off the hose leading to water pump and look up in the housing for bits of old impeller lodged below the cam in the waterway. Ask me how I know!

Edited by malibucat

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GlassMaster

Assuming your new impeller is functioning correctly.... with the boat on the water, remove the hose after the raw water pump or before the engine water pump (one side or the other - the side you can reach easiest) and then run the engine for a few seconds. Voluminous amounts of water should gush out of the opening. If it doesn't, keep looking for a restriction/blockage somewhere between the inlet strainer under the hull and the impeller inlet (such as the shut-off valve might have been bumped and is now partially closed). If water does gush, your water pump might be having a problem moving water adequately. You might also try removing the temp sensor and use a wire to free anything that might affect the sensor's ability to function accurately. Good luck!

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JonnyRad91

Well it sounds like sucking of air. I am going to keep going through everything and see if I can find anything. Something has to be sucking.

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tvano

don't overlook glassmaster's hint that the new impeller may not be healthy.

there are cases of infant mortality w the impeller rubber spinning on the metal core even w a brand new impeller.

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John I.

don't overlook glassmaster's hint that the new impeller may not be healthy.

there are cases of infant mortality w the impeller rubber spinning on the metal core even w a brand new impeller.

Experienced this just last year on a buddy's Mastercraft. Wasted a couple hours of prime water ski time before we thought to crank the engine with the impeller cover removed. Sure enough, shaft turned but not the rubber vanes.

Are you certain the engine temps you are witnessing are accurate? (gauge, sensor issues?)

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iliketoski

I had one of the hose connections on the inlet water line, the "T" fitting cracked and started sucking air. similar could happen on your strainer(?)

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evanlaczi

Mine is similar. I notice for whatever reason when my stereo is turned to on my temp gague rises. Could be bad gague. Or wiring

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JonnyRad91

So, did some further work on her. I recently had my stereo redone which included moving the heater so that could be the place that I am sucking air but at the moment I cannot get at it without taking a bunch of stuff apart. More telling... I think I ruled out a faulty temperature sensor. The starboard side exhaust manifold had steam leaking out of the nylon connector on the top side of the motor. That exhaust manifold was significantly hotter than the other side. So why might one side get hot and not the other and i guess the best question is, is the manifold overheating because of something else. the Teflon tape on the nylon connector has basically melted out.

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