Last weekend we were on the water and went to anchor and my wife said she could hear water coming in the boat. So I pulled the anchor opened the hatch and could hear it too. We took off ran the bilge and took the boat out. I found one of the hoses going into the sea pump loose so I put it back on tightened it up and started it up hooked to water hose. Then I looked and the whole impeller housing cracked. I took it off yesterday and the impeller was toast so I got a new impeller and housing and installed yesterday. I put it on started on the water hose and could see it was leaking some around it somewhere so I took it all back off checked the o rings and everything looked fine so I tightened it back down a little tighter than before ( was afraid to break the plastic housing). But I did notice a hairline crack in the metal where one of the bolts goes through the impeller housing to mount onto what connects to the housing and pulley. I didn't think that would have any effect. I put it back on and started it and could see a very small amount of water being slung off of where the pulley turned but couldn't even see where it was leaking. I turned the boat off and left the water running and with the boat off I could see a small stream of water start to come out off the top somewhere in between where the plastic and metal housings meet. I don't understand why it would leak more with the motor off and don't know what to do. I'm almost afraid to try and take it off and tighten the bolts anymore. And I really don't want to buy the 450 dollar metal housing and pulley if I can avoid it, especially if that doesn't even fix the problem. I'm stuck and very frustrated and would appreciate any input. Sorry so long and my boat has a 454 that was totally rebuilt between seasons and I just want to enjoy it not put more money into it.

there is a small seal on the bearing side of the stainless plate that is probably leaking. you can buy them seperatly from merc from the entire pump i think they come in a two pack cause there are two seals with a weep hole between them to protect the bearings. once the stainless wear plate is out i drilled a hole into the metal part of the seal and screwed in a screw. i then used vice grips with a slide hammer to get it out.

It leaks more with the engine off because you are using a garden hose which has pressure making the water flow to the pump. Normally there is only pressure on the output side of the pump when running.

I thought about that so I filled up a large tote with water and lowered the out drive into it. It seemed a little better but it still leaked a little and leaked more as before with the engine off.