Help in solving an Overheating issue

QC

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Re: Help in solving an Overheating issue

Cool . . . :)
 

Fun Times

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Re: Help in solving an Overheating issue

let me see if i got this correct...

the u joint bellow is used for the driveshaft and the exhaust bellows is where exhaust and water is discharged from the risers? these have nothing to do with water intake right?


the water hoses and connections in the bell housing can be inspected when the outdrive is out. However i can test whether a problem arises from the outdrive by removing the hose intake in the thermostat coming from the outdrive and checking the water discharge..should discharge approx 7ltrs in 15seconds right? if not the case i still can not elimate the hoses in the outdrive to be the problem as a restrction could be felt when engine is revved up and not at idle right?!


i really think there is a restriciton in the outdrive as the overheating speeds up when outdrive is tilted upwards...​
[There Could be a restriciton or A hole or A kinked or twisted hose down there, Also it could be at the oil cooler mounted to the engine some place]. hey boat tech...i really do appreciate your detailed explanation and links... [ No problem I hope one of them works and you find the problem. I know it is a lot too do so good luck too you with it.:)
 

clinche

Seaman
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Aug 10, 2007
Messages
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Re: Help in solving an Overheating issue

Don S - I went through the service bulletin. if i have air bubles between thermo and manifolds could that also be a blown head gasket?
 

clinche

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Re: Help in solving an Overheating issue

thanks boat tech..2 quick ones..
1. have any idea where to find the oil cooler on my 5.7 V8 engine? cant find it anywhere? should it be inline with the water inlet hose?
2. Compression turned out fine. do i need to perform a leak down test as well? cant i rely on the comp test only?

Thanks bro
 

Don S

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Re: Help in solving an Overheating issue

Don S - I went through the service bulletin. if i have air bubles between thermo and manifolds could that also be a blown head gasket?


Nope
 

Fun Times

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Re: Help in solving an Overheating issue

thanks boat tech..2 quick ones..
1. have any idea where to find the oil cooler on my 5.7 V8 engine? cant find it anywhere? should it be inline with the water inlet hose?
2. Compression turned out fine. do i need to perform a leak down test as well? cant i rely on the comp test only?

Thanks bro
Kind of hard to say where the oil cooler really is, They seem to move them around alot some times, But I am thinking it is mounted at the rear of the engine and the inlet hoes is going too it like in this link see number 22 and 11. http://www.mercruiserparts.com/Show...r=2697&bnbr=110&bdesc=Standard+Cooling+System. Also the leak down test is really a good idea if you can not find any that stands out in all your other testing, I know it is kind of a pain in the rear to do, But if you can't find any thing eles then yes you will need to do it because now a days it is just as important, If not more then a Compression test.:(:)
 

jtybt

Senior Chief Petty Officer
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Aug 5, 2009
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Re: Help in solving an Overheating issue

What kind of history did you get about the 'new' engine. Maybe 9 years of raw water in the ocean may have the block all clogged up. Did you check the thermostat housing for rust.
 

clinche

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Re: Help in solving an Overheating issue

Kind of hard to say where the oil cooler really is, They seem to move them around alot some times, But I am thinking it is mounted at the rear of the engine and the inlet hoes is going too it like in this link see number 22 and 11. http://www.mercruiserparts.com/Show...r=2697&bnbr=110&bdesc=Standard+Cooling+System. Also the leak down test is really a good idea if you can not find any that stands out in all your other testing, I know it is kind of a pain in the rear to do, But if you can't find any thing eles then yes you will need to do it because now a days it is just as important, If not more then a Compression test.:(:)

ohh ok i found it but as you said it is next to impossible to clean the hoses back there..no space to move and the heat makes it even worse :( i managed to found the water inlet in the gimbal housing and followed it to the oil cooler and then to the stat, water pump, manifolds and risers..however i dont think i iwll manage to clean the oil cooler..it is so far back :(

i checked the stat temp while running (140 stat not 160) with a laser temperature reader (like the ones u showed in the linked u sent me) and found a huge difference between it and the gauge..at idling it reads approx 120 when my gauge is reading 150..at 3800k it reads 140 when my gauge is reading 175..

i will be taking the termo sender in the stat and checking it out..if either the gauge or the sender unit is the culprit do u have to change them altogether for them to be compatible?

Thanks
 

Fun Times

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Re: Help in solving an Overheating issue

ohh ok i found it but as you said it is next to impossible to clean the hoses back there..no space to move and the heat makes it even worse :( i managed to found the water inlet in the gimbal housing and followed it to the oil cooler and then to the stat, water pump, manifolds and risers..however i dont think i iwll manage to clean the oil cooler..it is so far back :(

i checked the stat temp while running (140 stat not 160) with a laser temperature reader (like the ones u showed in the linked u sent me) and found a huge difference between it and the gauge..at idling it reads approx 120 when my gauge is reading 150..at 3800k it reads 140 when my gauge is reading 175..

i will be taking the termo sender in the stat and checking it out..if either the gauge or the sender unit is the culprit do u have to change them altogether for them to be compatible?
Thanks
No you should not need too in most cases, Just try one part then the other. Just buy [OEM] parts and every thing should work the same. What style gauges do you have??? I am sure you do not have a old/new gauge sitting around to try first, But that is what we sometimes do first before just adding parts all over the place. Also keep in mind if the temp sending unit is not getting the right ground it will do this, And the gasket might stop the grounding if sealant was used at the thermostat housing Gasket.
 

clinche

Seaman
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Aug 10, 2007
Messages
65
Re: Help in solving an Overheating issue

just came back from a day boating..engine temp alarm sounded when i was cruising at 3800 revs..lowered down to 3200 revs alarm went off..went back up to 3800 revs and alarm did not sound..need to check all water hose pipes for any leakages...
 

clinche

Seaman
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Aug 10, 2007
Messages
65
Re: Help in solving an Overheating issue

update

checked all water hoses..no blockages..took the lower unit off and replaced impeller which looked brand new..however i have been told that sometimes even though the impeller looks new it still could cause problems..

reved her up to 4K and all looked fine..hope i solved the problem but we have to wait for the weekend to be 100% sure :)

thanks for all the input guys..
 

clinche

Seaman
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Aug 10, 2007
Messages
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Re: Help in solving an Overheating issue

i have been told that a worn impeller will cause the engine to overheat at idle.
Could it also cause an overheat at higher speeds?
 

cr2k

Captain
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Mar 19, 2009
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Re: Help in solving an Overheating issue

Wow, just another check mark in the CON column for the Gen II.
 

clinche

Seaman
Joined
Aug 10, 2007
Messages
65
Re: Help in solving an Overheating issue

update..ran the boat at higher rmps this wekened and no overheat..so i can say that the culprit of the problem was a new impeller that i replaced..kinda strange but true..thanks for the input guys..
 

Bone fish

Cadet
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Mar 20, 2009
Messages
9
Re: Help in solving an Overheating issue

Can anyone tell me how to test the engine water circulating pump? I can see water moving in the heat exchanger at idle and the thermostat opens and closes (according to the temp guage). The raw pump is new and the riser gaskets are too. The heat exchanger is clean but the motor (454 inboard) runs hot above 3400 rpm.

Circulating pump is original, 1995 and has about 600 hours on it.

Thx
 

QC

Supreme Mariner
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Mar 22, 2005
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Re: Help in solving an Overheating issue

You should start your own thread Bone_fish . . . ;)
 
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