AQ170C Impeller does not push/pull water

[heryrg2711]

Hey guys, so i recently replaced my head and manifold gasket, i then installed the rocker bar incorrectly and bent two pushrods. I have replaced them and reinstalled everything correct. I also installed a new t-stat. Today i started the motor, it started well and ran well. But after a couple of minutes of running the impeller housing started to smoke. I turned the motor off and took out the impeller to check it out, looks good.
So i tried to suck the water in(through salt water filter, intake to impeller) with my mouth and i was able to get water. So the intake is not clogged.
I ran the motor for a bit(few secs) at idle with the salt water filter open to see if i can feel vacuum where impeller sucks, there is a bit of vacuum not too much.
I then tried to pour water manually into the impeller intake through the sea water filter, all two gallons went in. If oil cooler plug(6) is open water comes out when i pour in. If circulation pump drain plug(5) is open water comes out of there when i pour but nothing out of manifold drain plug(1)

Some more info; look at the pic of the manifold, i used some farenheit putty to seal up the hole. I'm afraid i might have sealed the channel inside, although there wasn't much putty. So i think this could cause some back pressure and impeller cannot not push the water. So i opened the exhaust manifold drain plug(1) and even then the impeller did not pump water.

I also opened the oil cooler drain plug and then i started the motor and water is not coming out of there, what the hell?? It's very close to the impeller and i think this would release enough pressure so it could pump.
Impeller is not chewed up.


Manifold hole

Drain plugs

 

[wellcraft19]

Re: AQ170C Impeller does not push/pull water

To me it sounds like a blocked exhaust manifold.

BUT, if you ran so the impeller housing started to smoke, you have a toast impeller, and likely also a toasted axle seal. You need to replace both of them before proceeding, as well as the gasket for the impeller housing cover.

Is your boat on dry land? If you run on "muffs" (or better the outdrive in a "bucket"), while also having the oil cooler drain open, and see water coming out through said drain, all points to a blocked manifold.

Reason for asking you to run in a "bucket" is that then you can truly see if impeller has enough suction to actually draw water in through the drive (if running on muffs correctly placed and "sealed", water pressure might be enough to "help" the impeller along). If no water coming , you have a vacuum leak (axle seal, hose clamp that is not tight), a pinched hose, etc.

And, maybe needless to ask, but is the "cam" installed inside the impeller housing? W/o a cam you can have the impeller spin forever, still not water will be pumped through. Maybe not needed to say, but impeller does not really pump based on the "rotation", but rather the change in displacement as the impeller fins travel (rotate) over the cam (hence, not like the regular circulation pump on an engine).

 

[heryrg2711]

Re: AQ170C Impeller does not push/pull water

thanks wellcraft. check the pics of impeller bellow. It doesn't seem burned, the integrity of the rubber seems almost as good as new. The fins are slightly bent, due to the its position in housing, i think.
About the axle seal. I'm not sure where it is supposed to be. Is it like an oring on the shaft?
The shaft comes out easy. when i was taking the impeller out, the shaft started coming out, so i pulled it out to check it out, probably not the best idea, i know. Did not see a seal on the shaft. Is it embedded in the housing around the shaft, i didn't look inside the housing
The shaft key is in place.

I was running the boat on land in a bucket. And i could suck the water in by mouth.

Today i took off the manifold and it's not clogged, atleast where i sealed the hole. Maybe when the welder had it he stuffed some crap inside, i will check the insides tomorrow.

 

[wellcraft19]

Re: AQ170C Impeller does not push/pull water

Agree, impeller looks good. Cam in place?
Not sure which pump you have, but check this link to a few drawings of AQ170 pumps (http://www.volvopentastore.com/Marine-Gasoline-Engines-for-AQ115A-AQ115B-AQ130-AQ130A-AQ130B-AQ130C-AQ130D-AQ165A-AQ170A-AQ170B-AQ170C-AQD21A-BB115A-BB115B-BB115C-BB165A-BB170A-BB170B-BB170C-MB20A-MB20B-MB20C-MD21A-7736850/dm/*******.964036560--**********.288121016--store_id.366--view_id.765086). Seems to be two axle seals (think my AQ171C pump with what looks to be a very similar impeller, only has one).

The gasket for the lid is not so thick so there's an empty cavity between lid and impeller (need to seal firmly)? You can always try with some glycerin (think KY) to lubricate impeller and see if it'd start to work.