Chris288

ran over a mud/weed bar in RI over the weekend at idle in a long no wake zone, seems I sucked a bunch of junk into my HO. shortly thereafter the high temp alarm went off, right before the end of the no wake, she was at 180 degrees. let her cool off a bit and tried running again. water pressure seemed low at idle, but fine at speed, water temp seemed to act a bit flakey, running 160 and 175 but never setting off the alarm again for the rest of the day. Trailered her home and flushed on the hose, suction at idle on the hose does not seems as good as it once was and the water exiting the tail pipes seems a bit warmer than normal... Long story short, she seems to be running a bit hotter than normal but no alarms are going off, before I pull the impeller to see if I scored it, is there any way to back-flush the close cooling system ?? any other suggestions ??? Thanks Chris...

Chris288

Anyone ????????? Do the end caps come off the exchanger to flush it out ???

turnerrd

Chris,

Here is a quote from a post back on 8/4 on how to back flush a 496. Hope it helps.
Harper,
Something you may try, facing the front of the engine the lower hose, on the right hand side of the heat exchanger ( about 1- 1.5" diameter) can be removed, then remove the 2 blue drain plugs from the sea water pump. Hook up a water hose to the hose you have removed and back flush the engine. This is a quick, and easy way to flush any blockage from the oil coolers. Especially if you have twins, and access is difficult. I found a common fitting at the hardware store, that would allow me to clamp to this hose and get good pressure back through the system. The amount of debris that came out was alarming. You are definitely having a water flow problem if the exhaust is getting this hot, on the one side.

The back flushing may resolve this, but if this does not work, do not rule out, your pump housing may be worn out. As I said in an earlier post, I had to replace both of mine after 60 hours. The brass housings will erode in time in a river environment, and new impellers will not help, if they are worn out.

One other possibility, the 496's had an issue with the fittings on the lower side of the exhaust manifolds corroding and breaking. A recall was issued to replace these a couple years ago, to replace the original brass fittings, with aluminum ones. Even if this is not your problem, I would make sure this has been changed, before it is a problem.

Good luck, let us know what you find.

turnerrd

What temps do you guys see normaly on your 496? I usually am around high 160's maybe low 170's when up on plane and running regardless of speed. When I come off of plane and I go up to about 175 maybe 180. As soon as I get on plane it goes right back down. No alarms or guardian mode ever. What temp does guardian mode happen at?

Chris288

Thanks much appreciated.... My temp never budged from 160 ever.... now it fluctuates between 160 running and 170-175 at idle... guardian mode came on for a split second at 180...

Anarchy Powerboats

If you have sea strainers you need to pull out all the screens, I did the same thing last summer and I picked up more silt than anything else.

hp500efi

155 degrees I run no matter on plane or not 160 tops

twin's

turnerrd

yeah but it looks like ou have hp 500's . Not closed cooling like a 496

turnerrd

Chris,
Mine seems to be acting exactly like yours. Let me know what you come up wtih as your culprit. I'm going to back flush and go ahead and change my impeller. I'll let you know what I come up with.

turnerrd

Took the pump out and when disasembled I saw the large scoring marks on both the body and end plate. Just ordered a complete pump assembly (PN 46-862914A2) from BAM. My question is does this include the shaft and pulley along with the impeler and o ring gasket? Probly not the mounting bracket or pressure sensor though. I think a saw previous thread on this a while back and they said it did include the shaft and pulley. Does any one know for certain.