Penta 4.3 Overheating

[JimBobJackson]

Buckle in for this one. Hoping someones experienced this exact thing.
1)replaced impeller, yes it was destroyed. I wasnt aware theses should be changed more often.
2)pulled off water pump. still works
3) flushed entire system with fresh water garden hose( did see bits of the old impeller)
4)thermostat is opening but I cant seem to get good flow up to the exhaust hoses.
5)chased down the sea water intake hose suspecting a hole or crack. I sprayed water from the impeller down through the sea water intake hose to check for leaks. then sprayed up from the water intake on the prop. Dont see any obvious leaks. Is there a better way to test that hose and what am I missing?

Thanks!
Kevin

 

[Scott Danforth]

Volvo recommends changing the impeller every 2 years
what vintage?
did you check the pot-metal or plastic fitting at the drive where the raw water hose is connected?
pull the hoses from the thermostat housing and back-flush to get all the pieces out?

 

[JimBobJackson]

Volvo recommends changing the impeller every 2 years
what vintage?
did you check the pot-metal or plastic fitting at the drive where the raw water hose is connected?
pull the hoses from the thermostat housing and back-flush to get all the pieces out?

I’ve had the boat 2 years. The doctor that had it before me knew nothing about boats so I’m sure he never changed it.
the fitting looks ok. At least it didn’t show a leak when I back flushed.

 

[Lou C]

If your impeller was shredded the bits probably are in the thermostat housing, because that's the next place along the water flow route. You'll have to pull the housing (get a new gasket), dig out the rubber ring that holds the stat in the housing, test the stat in a pot of hot water (should open at about 160*F, that is standard for most Volvos). If its good you can reuse it but if bad replace. Then clean out every port in the stat housing including the bypass port that is hard to see. Hook up a garden hose to the hoses that feed the manifolds and flush them out, make sure you have good water flow out the bottom of the transom mount. After its all cleaned out, reinstall with a new gasket.
The water nipple that can crack is not the one in that pic you posted (that one is metal), it is in the pivot housing, you can't see it unless the drive is pulled.
What you can do as a test is this:
tape over the water intake holes on the drive with duct tape. Tilt it up enough that you can see the hose that goes from the pivot housing (what the drive is bolted onto) to the gimble housing (that's the fitting in your pic). Now disconnect the raw water intake hose at your impeller housing, hold it up and fill it with water. Have a helper go to the back of the boat to see if there is water leaking from where that hose goes into the pivot housing, if so you probably have to replace that fitting, if not good, remove the duct tape from the drive intake holes.
These raw water cooling systems depend on a lot of cool water in and warm to hot water out, anything that impedes flow will cause overheating.
Your engine with a 160 stat should run from about 160 to about 175 or so.

 

[JimBobJackson]

If your impeller was shredded the bits probably are in the thermostat housing, because that's the next place along the water flow route. You'll have to pull the housing (get a new gasket), dig out the rubber ring that holds the stat in the housing, test the stat in a pot of hot water (should open at about 160*F, that is standard for most Volvos). If its good you can reuse it but if bad replace. Then clean out every port in the stat housing including the bypass port that is hard to see. Hook up a garden hose to the hoses that feed the manifolds and flush them out, make sure you have good water flow out the bottom of the transom mount. After its all cleaned out, reinstall with a new gasket.
The water nipple that can crack is not the one in that pic you posted (that one is metal), it is in the pivot housing, you can't see it unless the drive is pulled.
What you can do as a test is this:
tape over the water intake holes on the drive with duct tape. Tilt it up enough that you can see the hose that goes from the pivot housing (what the drive is bolted onto) to the gimble housing (that's the fitting in your pic). Now disconnect the raw water intake hose at your impeller housing, hold it up and fill it with water. Have a helper go to the back of the boat to see if there is water leaking from where that hose goes into the pivot housing, if so you probably have to replace that fitting, if not good, remove the duct tape from the drive intake holes.
These raw water cooling systems depend on a lot of cool water in and warm to hot water out, anything that impedes flow will cause overheating.
Your engine with a 160 stat should run from about 160 to about 175 or so.

Thanks for the response.
I pulled the stat yesterday as part of exhausting all components. It only appeared rusty, but I know it works because the water will flow to exhaust only when filling the top bleeder while its hot.
I feel like I've gotten all the old loose rubber impeller blades out when I backflushed with the hose.
I can spray up the sea water intake and get a decent flow out of the same hose at the impeller housing.
I also pulled the power steering cooler on that same coolant branch, with no flow issues there.
Trying to get around pulling the transom, but I'll try what you mentioned tomorrow. (as long as I understand correctly)

 

[Lou C]

you want your temp to look like this....

 

[Wave34]

On my 5.7Gi, first ride of the season I got overheat.
I tested everything, then found that behind the raw water pump there is a seal on the shaft. It was worn and was letting air being sucked inside the pump, so, water was not sucked as much from the outdrive.

For a test, disconnect both hoses of the RWP. Block the exit of the pump, and make an adapter to connect a hand held vacuum pump on the inlet, and pump some vacuum and see if it holds it.
If not, the seal is leaking. I bought a double lip seal from my local bearing shop. Volvo had only a single lip seal, and won't sell you only the seal, they sell the whole pump a$$y.
That solved my overheating problem.

 

[dypcdiver]

I second Wave34, similar thing happened to me after an impeller shed some fins. Dry pump overheated and destroyed the seal. I rebuilt it with new seal and bearing for less than $50.

 

[Lou C]

Great tip!
also if you can find it, see if you can find and print out a document called "volvo penta overheat diagnosis" it covers this and other points you want to make sure to check out.
One other thing, a poster on here had the water tube rot out that allows water to flow from the lower drive to the upper drive housing, this caused overheating on plane but since its inside the drive, was not easy to figure out.

 

[JimBobJackson]

Hey guys, sorry I havent updated. Im 99% sure I've got a "vacuum leak" somewhere between the sea water intake at the bottom of the outdrive, and the hose going into the boat at the top of the outdrive.
I'm having a hell of a time finding info on that area. Do I have to take off the whole damn thing?
It's a SX-M 1.79
Thanks,
Kevin

 

[Scott Danforth]

Hey guys, sorry I havent updated. Im 99% sure I've got a "vacuum leak" somewhere between the sea water intake at the bottom of the outdrive, and the hose going into the boat at the top of the outdrive.
I'm having a hell of a time finding info on that area. Do I have to take off the whole damn thing?
It's a SX-M 1.79
Thanks,
Kevin

removing the outdrive is an annual service requirement

it also makes getting to the fitting I mentioned in post #2