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Another 470 getting warm

"So just how much water should

"So just how much water should an impeller pump?
1979 470 w/ heat exchanger.
I put a new impeller in last week. The old one was missing a fin. This impeller really never pumped that much water to begin with. Never a steady stream.....more like a light rain.

I am having overheating problems hence the replacement. While replacing, I took out old impeller parts that were stuck in the housing. Installed the new impeller, new gaskets.....the whole kit. I am still overheating and the new impeller just doesnt seem to pump enough water.

Should there be a steady stream? Should I be looking for obstructions? I took off the water inlet grills but found nothing there.

Any ideas on where I should start?"
 
Steady stream? Yes. Is the i

Steady stream? Yes. Is the inlet hose on the OD pinched? Heat exchanger working?
 
"Well the longer I let it run

"Well the longer I let it run the hotter it gets. I shut it off at just under 200.
I had the heat exchanger gone through 2 years ago. At the same time I did an impeller and thermastat.

It takes about 15 minutes on the muffs at idle to heat up, alot less time above idle.

I looked at the hose....no pinching although it seems weak and wore out. I dont see any collapsing going on while running.

Ive had this boat about 6 or 7 years and it never really pumped much water. Other than the heat exchanger problem this is the first time it has overheated.

The AF is fresh as well as the oil"
 
"Check the elbow for clog. The

"Check the elbow for clog. There is a solid gasket underneath elbow the retain the coolant, but the raw water hose it still injeting water into the pipes.
Possible big bucks here. The manifold is a $1000 from Merc if the deck is bad underneath."
 
Impeller I put in last weekend

Impeller I put in last weekend..I pulled the hose off the heat exchanger and it is pumping water but not alot.

Is the exhaust vaporizing the water as it comes out?

I ran the engine with the radiator cap off.
The stat seemed to open ok at 160 but flow was very limited and slow? Even at 190 where I shut it down.

Is there any way to check the circ. pump without tearing it down?
 
When I look in the coolant fil

When I look in the coolant filler neck while running at operating temp it seems like I should be able to see coolant flowing like in a car radiator? I know that it's basically a tank and the inlet and outlet are the same but it seems I should see some motion there when the stat opens.

Stat I put in 2 seasons ago. Could it be bad already? I guess I'll pull it and test it next.

I pulled the inlet cover off the circ. pump and all looks good there as best I can tell.
 
Ok I pulled the stat and it te

Ok I pulled the stat and it tests good.

Is there a way to test the circ. pump? I can pull the inlet cover ........its all together and doesnt look damaged. What else should I look for?
 
"Take the hose off the inlet f

"Take the hose off the inlet from the drive the water should flow like a garden hose if it doesnt check to make sure you installed the impeller in the correct rotation. If its not flowing like a garden hose its either the rubber hose between the drive and the through hull 90, the impeller,or an obstruction in the screens of the drive."
 
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