This really sucks... Sand that is.
 

Had a bad day this week. I got into some shallow water and before I knew it the enginge temp was over 200. I shut it down and driffted to deeper water and checked the pick-ups for obstructions. When I re-started the temp went right up again. After getting a tow home I pulled the raw water pump. It was trash and full of sand. I pullesd all the water hoses and they were packed with silt. I flushed everything front to back and top to bottom. After installing a new raw water pump. I hooked up the hose and started her up. At first it would not suck up the water (low water p/u) so I held my hand around the hose adapter to force the water up to the pump. A little mucky water came out of the pipes at first then cleared up. The temp slowly rose to 170 then leveled off. I noticed that the water on the right side was warmer than on the left. Also after re-startinting I had to again hold my hand around the pick-ups to prime the pump.
I never had to do this before. Could the new impeller have gone bad with a few secounds of running dry? I lubbed it w/ soapy water before instaling. She dosen't seem the same. Any insight would be appreciated.
THANKS,
Chris

it could have gone bad. west marine sells an impeller that is supposedly good for 15 minutes running dry. do you have a strainer and did you flush that first. may be you sucked up more sand.

Sounds like you are sucking air somewhere - check all your hose connections.

Do yourself a favor and throw that damn low water pick up adapter away. Take the hose off the INSIDE of the top of the drive and put the end of your garden hose right into this hose. This garuentees that you will have water at the pump when you light off the motor. You can do what I did and get one of those $1.50 on/off switches for your hose and add 2' of old hose to it. This way you can do this alone and not completely fill your bilge when you turn the water on. Works like a charm. There is a kit available that splices into your inlet hose, between the drive and the pump, that allows you to simply hook up your garden hose. But it's kinda pricey, so I think my alternative is pretty neat (read: cheap).

I did the same thing you did over the 4th of July weekend. Didn't really hurt anything though. Replaced the impeller with one that I got at Boat US (supposed to be able to run dry I guess, whatever, I'll use water thank you). Kept the old one for a spare (it looked good, but since I had the pump apart.....you know).

But take my advice about the water thing. It's easier and better for your motor.

Mike

Yes, you might have smoked another impellor. but if you had that much mud & silt in hoses the engine is full of mud/sand. You need to remove the drain plugs on the side of engine block. If no water comes out need to stick wire or something up in hole to get water to start flowing. There is drain hole on each side of block. Run water thru motor untiil water comes out clear.

You might want to double check your engine oil cooler. It has small tubes running through it that commonly plug up whith sand and debris when you have this type of trouble with sand and pump impellers. Some times you can back flush them but it is better to pull them off and look through the tubes. You can use a small piece of welding rod to clean out tubes if needed. Even if I have not had impeller or low water problems you have I check it ever year as part of my pre season tune up just to make sure.

did you replace the whole housing and impellor or just the impellor itself??

Thanks for all the replies. I removed all of the external hoses and back flushed all of the coolers. I will double check all the clamps sat AM and try draining the block. where would I find the plugs in the block. I hope you don't mean freeze plugs?

I also replaced the housing with the impeller.

There is a threaded plug on each side of the block that you use when you winterize to get out the water. Check your Merc manual that came with the boat. Did you back flush the hose from the drive before installing the new impeller?
Dan