how to backflush a 496 ho
 

Hi, i have never owned a closed looped 496ho before. It runs a little hot after a few wide open runs. I am going to check the sea pump but how and what do i flush. I have been told to flush the heat exchanger and hoses. Is it posible to screw anything up if i do it wrong? how and were would i install a gauge to check water pressure? any help would be great. Pics would be awesome. sorry to be an ignoramus. Oh, if it matters it has a whipple kit. Dustin whipple has been a big help on what to check and flush, i just dont know how. Thanks!

I had trouble with overheating a couple of years ago. I checked the heat exchanger by pulling the end caps off & looking through. That wasnt the problem, the oil cooler & p/s cooler are before that in the cooling system. I took the inlet hose off the heat exchanger & put a spray nozzle in the hose to backflush. Worked fine for me. The waterpump housing is a problem as the ends get grooved & reduces water pressure. Hardin marine makes a stainless housing replacement for about 350.00 as compared to 600.00 for merc. Hope that helps, Randy

Order a scan tool. It's a smart investment for anyone with that engine. It will allow you read the seawater pump pressure and the the various temperature sensors so you're not shooting in the dark.

http://www.rinda.com/marine/marine.htm#merctool

Disconnect the downstream hose from each of your coolers (oil on the front, power steering on the back of the motor) by loosening the hose clamps and sliding the hose off. Sometimes they are had to get off, I used a very small flathead screwdriver working parallel to the hose to loosen it. Don't pry up or you will tear the hose. Then take the big hose loose on the front of the motor. Blow water backwards thru the cooler and engine. Most likely you have some passages of the oil cooler blocked, causes engine to run hot and oil pressure to be lower.

That info was sent to me when I asked the same question by another oso member (knockld ) I did exactly what he wrote ( what I forwarded to you ) and it fixed my problem. The guys here are awesome and always willing to help!

Rick

You guys are awesome! thank you!!!! will let you know if it helps.

+1

You should have 3-4 lbs at idle.

When was the last time you changed your impellor?

just bought the boat. previous owner didnt know much about boats. So i dont thing impeller was ever checked. Boat is on its way to me now. How do i check water pressure at idle and at speed?

duh, i didnt read the post in front of your. i will order the tool.

You said your Temps are getting up there, do you know if there is a separate water pick up for your inner cooler, or is it one pick up teed off?

As soon as you get the boat I would .....

1. Change motor oil
2. Change gear oil
3. Change impellor.

This way you have some kind of maint. baseline. Those 3 things are pretty easy to do yourself.

Might change the housing as well!

i dont think it has a seperate pickup for the intercooler. could this be a problem?

great advice! i will do and also change the plugs and do a compression test.

If the one pick up is feeding the inner cooler and the motor it could be, the water is going to take the path of less resistance, which would rob your motor. Just a guess, I have a whipple as well and I had to reduce the water going into the cooler so my motor would get more water flow. What kind of whipple set up do you have?

makes sense. the boat has a 496 ho whipple kit

You have any pics of the boat and motor? ( what type is it )

how do i post pics? when i go to post it asks for a url link??? they are just pics on my computer not on a web sit some were.

good advice, i will. cheep insurance

You are just registered, you can't, unless you go to photo bucket and do some tricky Stuff, you can email them. [email protected].