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Impeller Problem? Alpha 1 gen 2

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settimo velo

Contributing Member
Back on the Settimo Velo getting ready for sea trials at last! However, My image.jpgcounter rotating drive isn't picking up cooling water from the flush muffs following the service I did. Nothing getting through to the engine. Standard rotation drive is fine, so I got that right! The manual calls for the impeller blades to be curled counterclockwise, so I thought this was right (see picture)? If it is right, where else could the problem lie? ... The drive is engaging and prop rotating.
 
Your forcing water with the muffs and nothing is getting to the engine the fitting that goes thru to the transom might be clogged ?

Backflush with the drive off, just remove the hose that comes into your engine at the first point maybe the t-stat or exchanger.

The hose kinked outside the transom drive side?

The new housing was installed with all the seals ? You read that right " the new housing " !
 
try to put it into a bucket of water sometimes they wont spray out the pee hole on the muffs if you put it in the lake or bucket it will give you back pressure but the impeller should end up correcting itself if you have it oiled use olive oil not petroleum based or will swell the rubber of the impeller
 
Remove the incomming water hose where it connects to the thermostat housing, (raw water cooled???)

start engine and see if any water is flowing.

the key here is determining wether it is a lack of water comming in or a lack of water being allowed to go out.

So start with water comming in. If the water supply looks good and a good steady volume of water is flowing then it has to be a water out blockage.

once you determine this report back and we can go from there
 
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Thank you all for the replies. When I detected the problem I pulled the hose off at the thermostat housing (yes it is raw water cooled) to check for water coming through with the engine running, but there was nothing. I then removed the bottom half of the drive to check the condition of the impeller, which looks OK to me although I didn't replace it when I serviced the drive and it's been standing now for a while! I then checked for blockage by pouring water down the hose removed from the thermostat and it went straight through, so that seems to be clear. So, I think the problem is lack of water coming in, being picked up by the impeller ... I'm thinking that I should get a service kit to replace the impeller and seals around the impeller housing and outlet tube etc. or is there anything else I should look at first?
 
Took a closer look at the impeller housing to find some wear, although I'm not sure how much this would lower performance. There are grooves in the plate and housing about 1/32 deep worn by the centre of the impeller. The impeller itself looks worn down a little on one side and there is some wear on the ends of the blades caused by the outlet slots in the housing. None of this looks that bad to me! How reliable are flush muffs when it comes to lifting the water to the impeller? Anyway, now it's out I'm thinking new impeller, gaskets and face plate?
 

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settimo velo said:
Took a closer look at the impeller housing to find some wear, although I'm not sure how much this would lower performance. There are grooves in the plate and housing about 1/32 deep worn by the centre of the impeller. The impeller itself looks worn down a little on one side and there is some wear on the ends of the blades caused by the outlet slots in the housing. None of this looks that bad to me! How reliable are flush muffs when it comes to lifting the water to the impeller? Anyway, now it's out I'm thinking new impeller, gaskets and face plate?
Click to expand...


Your impeller is set, hence it will not work efficiently.
Get a quick silver or Mercury impeller kit without the housing. I sand the inside of the housing with a little 1000 grit paper, add some soap and reassemble. Do not forget the rubber that slides down over the shaft after the housing is back on. Put it together with the new impeller and it will be fine.
 
That water pump system is a very good and forgiving design.
It was the type used by johnson and evenrude outboards forever.
When merc came out with the alpha 1 gen II they went with this design.
High volume low pressure. Alpha 1gen 1 and all prior years including most outboards
All used the high pressure low volume riggid style impeller.

All that being said. If you had no water at the thermostat housing after removing the hose
then you need to remove the outdrive. Back flush and see if water flows out of the gimbal housing
freely. If it does then something in the drive is causing the flow issues. If not the something between
the thermostat and gimbal housing is causing the restriction.

Not that replacing a worn impeller is good thing but i would suggest that it still should move water
especially if using a hose source.....

I use muffs all the time with NO issues.....
 
The manual calls for the impeller blades to be curled counterclockwise, so I thought this was right (see picture)?
Click to expand...
CCW shown in the picture w/the cover upside down but installed the impeller will be CW. It's been a few years for me...I could be wrong...turn it around?
 
kghost said:
That water pump system is a very good and forgiving design.
It was the type used by johnson and evenrude outboards forever.
When merc came out with the alpha 1 gen II they went with this design.
High volume low pressure. Alpha 1gen 1 and all prior years including most outboards
All used the high pressure low volume riggid style impeller.

All that being said. If you had no water at the thermostat housing after removing the hose
then you need to remove the outdrive. Back flush and see if water flows out of the gimbal housing
freely. If it does then something in the drive is causing the flow issues. If not the something between
the thermostat and gimbal housing is causing the restriction.

Not that replacing a worn impeller is good thing but i would suggest that it still should move water
especially if using a hose source.....

I use muffs all the time with NO issues.....
Click to expand...

I think it should move the water too but now that it's out I've ordered a service kit.

With the bottom half of the drive off, I've just poured half a gallon of water down the pipe that comes up to the thermostat housing. It all came out of the other end (the copper feed pipe in the upper drive) very easily and as quick as I was pouring it in, so I'm convinced that there's no obstruction in the pipe, through the gimbal or in the drive...

I'm beginning to wonder if I've had a problem with my new Sierra flush muffs. This is the first time I have used them so maybe I just didn't open the tap up enough, or the water pressure in the workshop was could have been low ... it can be a problem in my area from time to time.

I'll put it all back together next week and post an update.

Thank you for your thoughts and help, which are much appreciated. Mike
 
Master mechanic said:
The truth is a submerged drive is how to test if your impeller is moving water.
Click to expand...

Agree,

Also one of the tests i have done is to hook up the muffs and turn on the water only a small amount of flow. start engine and if the impeller is working it will suck all the water in. if the low water flow continues to blast out the sides of the muffs that would indicate a bad impeller..

either method should work. But if a new housing and impeller is installed you should be good.
 
settimo velo said:
Thank you all for the replies. When I detected the problem I pulled the hose off at the thermostat housing (yes it is raw water cooled) to check for water coming through with the engine running, but there was nothing. I then removed the bottom half of the drive to check the condition of the impeller, which looks OK to me although I didn't replace it when I serviced the drive and it's been standing now for a while! I then checked for blockage by pouring water down the hose removed from the thermostat and it went straight through, so that seems to be clear. So, I think the problem is lack of water coming in, being picked up by the impeller ... I'm thinking that I should get a service kit to replace the impeller and seals around the impeller housing and outlet tube etc. or is there anything else I should look at first?
Click to expand...


Are you sure that when you installed the lower unit to the upper that you hit the delivery tube that goes from the water pump housing to the upper drive delivery tube?

Also check that there is a drive key between the impeller inner bore to mate to the vertical drive shaft!
is possible it was overlooked.
pgood luck, I will follow this thread.
pGary
 
I dropped the lower drive unit, replaced the base plate in the impeller housing and fitted a new impeller. It's working great now:http://www.youtube.com/watch?v=w-IKSGiZHWs To be honest the old impeller looks fine to me and I am now suspecting a possible water pressure issue at the flush muffs as the cause! Re-assembling the upper and lower drive units on my own - with the upper still attached to the boat - was a challenge but I devised a way to do it with some big G-Clamps on the cavitation plate, taking care to line up the delivery tube (from the impeller housing) once I got the drive shaft located in the upper housing.
 
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settimo velo said:
I dropped the lower drive unit, replaced the base plate in the impeller housing and fitted a new impeller. It's working great now:
To be honest the old impeller looks fine to me and I am now suspecting a possible water pressure issue at the flush muffs as the cause! Re-assembling the upper and lower drive units on my own - with the upper still attached to the boat - was a challenge but I devised a way to do it with some big G-Clamps on the cavitation plate, taking care to line up the delivery tube (from the impeller housing) once I got the drive shaft located in the upper housing.
Click to expand...
 
I have the same issue. Impeller won't push the water. I took out the amazon after- market kit, bought the quicksilver OEM. this is the 4th time I have removed the bottom unit. I have done all the tests you have done. I even checked the muffs, if they are not aligned correctly water wont fill the water dam. Put everything back. Backflushed the whole engine prior to reassembling. I will take boat to the ramp and put in the water to see if anything changes.
This started because engine was getting hot, when I pull the lower drive found impeller broken and full of gear oil. Fix all the issues, new impeller and seals and replace impute shaft bearing. No more oil leaks, prop turns so impeller turns. I will post as to what happens when boat is in the water.
 
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