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Sierra vrs Mercruiser housings

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srdancer90

Regular Contributor
"OK, I have had it, I changeg

"OK, I have had it, I changeg my water pump lower assembly as well as the uperr assembly every season, yet there is still air bubbles being delivered to my engine causing an over heat issue. I just noticed a Sierra housing on e bay, I am interested in two things
1. Are they as good as the OEM
2. Is the swaping of the gears in the lower alpha 1 gen 1 that I have now a real difficult task?"
 
"It is not the OEM parts that

"It is not the OEM parts that are the problem.
You have to be doing something wrong
or you are getting the wrong parts or you have another issue causing the overheating.

Why would you replace your water pump impeller housing (upper and lower) every year??

If you are 100% sure that everything after the impeller housing is good with no restrictions the you are overlooking something.

Give us more INFO!!!

What outdrive do you have? I, R MR, Alpha 1 I or Alpha 1 II??

Under normal usage ~ 100 hours a year they should last for 3-5 years without failure."
 
"air bubbles at idle and overh

"air bubbles at idle and overheat , bubbles at cruise and overheat?
bubbles could mean sucking air or a head gasket leak"
 
"Alpha 1 gen 1 drive, the base

"Alpha 1 gen 1 drive, the base was replaced last season, the upper water pump impeller and housing are replaced every season. The boat has had this issue for two seasons, the first time it happened the arlams went off and I shut the engine down, the water pump was changed after the alarms went off ( 200 degrees.) There is no water in the oil, I have not done a compression test yet. However, I have twin engines and the drives were switched and the problem occured ion the starboard side, so it makes me believe that the problem lies within the drive. The problem drive is now on the port side, I had a merc tech run the boat with a clear plastic hose and he saw air at idle as well as under a full load. Both engines were tested and air did not appear on the starboard side. The hose in the bell housing was changed however the hose to the oil cooler remained unchanged. If the air is being entered from the oil cooler into the T-stat housing, could it be from a cracked head gasket?"
 
"Air will not enter the water

"Air will not enter the water stream from the power steering oil cooler. You would get power steering fluid.

If the problem transferes with the outdrive then the outdrive is to blame.

YOU must remove the outdrive and split the cases and do a thorough inspection of the lower unit from where the water enters the outdrive to the water pump, Look for debree in the path, Remove the pump base assembly and inspect the gaskets for correct placement and look for torn gaskets. Sometimes when installing a pump base the gasket is put on after the oring and it can tear the gasket. ( ask me how I know!!)
If the pump base is good and all the gaskets are clean with no debree or tears the the Stainless steel plate that is SANDWICHED between two gaskets must be inspected.

If all that looks good the you look to see if the 1/4 inch thick square rubber oring is sitting on top of the impeller housing. This o-ring is to keep exhaust from entering the water pump housing.

If that is there and is in good shape the look at the pump housing rubber that seals the 1/2 inch copper tube. if that is good look at the upper gear case (upside down of course) and inspect the plastic water thingy( forgot what it is called.)
This also has a rubber seal for the 1/2 inch copper tube. If the plastic housing looks at all melted then replace it!!!!All the time look for debree in the water path.

If all that is good the the only other location for air to possibly enter the stream would be the o-ring between the gimbla housing and the outdrive.

Just so you understand, 90 % of the time when air is getting into the incomming water stream it is exhaust that is getting in where the water pump housing sits. It is in the exhaust path."
 
"Kg. called the water pocket c

"Kg. called the water pocket cover.
Bubbles in the stream from the drive can only come from the low pressure side of the pump a bad base, warped base, or poor gasket contact.
reinstall the base gasket using contact cement.Above the pump is positive pressure, you`d only get leakage there"
 
"Ok, When I installed the base

"Ok, When I installed the base I did not use any gasket cement, I think it was a spray type contact. And I didn't use any contact cement on the gaskets either. Can I use the bellows adhesive on the gaskets and along the side of the lower base assembly when I install the water pump kit. That is remove the base assembly and use bellows adhesive along the sides of the base as well as along the bottom of the base. This will ensure that there should be no air being alowed into the lower. Can I use the bellows adhesive on the bottom of the water pump cover as well. A comment in point, I have twin alpha drives, and the starboard side water pump was installed (by me) no differently than the port side, no air being delivered in the starboard side"
 
BT
Exhaust gasses can get in

BT
Exhaust gasses can get in anywhere in the drive/pump cavity. The water system can act as a syphon and the exhaust gasses being warm to hot under very little pressure can be drawn in. Especially at the top of the water pump housing if that big square oring is missing.

I agree if parts are bad there will be a leak due to water pressure but there will also be hot gasses infiltrating those same locations.

What you said would be more likely true with thru transom exhaust.

Just my thoughts
 
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