help with my 496ho over heating!
 

well here it is. first last week my alarm went off, solid tone! found that my starboard exhaust temp (on port motor) was melted into the maifold! so I replaced the temp sensor! now I get a solid alarm after I take off but it it does weired things. A few times the temp went up past 180, but not all the time. Water coming out is steamy?! I toke off the seapump but its tight and all paddles are intacked no signs of wear? any ideas? some off the old sensor might have droping to the water side of the manifold could it have block somthing? there is steam on both sides tho?

How did the sea pump housing look? If there are any groves on the plates it will not work properly. Check the inside of impeller in the housing, that seems to be the first side to not seal. Just at a glance it may look fine but it has to be a very tight seal for it to work properly. Also if just one side does not have water coming out there probably is some blockage and it needs to be back flushed. Don't forget to check the oil cooler and the ends of the heat exchanger.

how do you back flush it?

Sounds to me like what's left of your last impeller is still in there. I am.not sure how to flush a 496, but on my 454s, I remove the water line at the discharge side of the pump, remove the lines at the thermostat and also the oil coolers and flush water thru them until all the rubber pieces come out.

I have all the lines off and i see no sign of any old or new rubber!

well took sea pump all the way a part impeller looks good no signs of any wear, inside housing is good, no groves, however it has groves on the ends in the middle but looks like they were machined in to it?

It should be smooth, no grooves...you have wear.

The 496 has closed cooling doesn't it? Make sure you have no blockage at the heat exchange, main cooling line from the drive, water intake on the drive and the manifold. I didn't think the pump housing had grooves, I would change it out.The fact that you said earlier that the water temp would spike then come down sounds just like what happened to me when my water pump failed due to blocked cooling line. I had to flush all the hoses and change the impeller again. Hope.this helps, its all I can think to check.

both the top and bottom have the exact groves the inside of the housing is a smooth as a babys bottom! i will post a pic tommorow.

There should be no grooves what so ever...everything should be smooth....the ends will look like the grooves were machined but there not.....it is suppose to be smooth! The design of the brass sea pump is bad, once sand goes thru it and the temp begins to go up the circulation is down causing this. Just change the pump and don't do any further damge to the engine. Hardin marine makes a stainless replacement that is cheaper than the stock merc pump and is better.

http://www.hardin-marine.com/p-15774...d-502-mag.aspx