How to flush a Merc 470 cooling section

[bucnon75]

1987 Merc 470 (3.7L), Alpha 1 Gen 1
Ebbtide Riviera 180

I believe the engine is running too hot and I don't believe my temp gauge is accurate. After running at idle (on muffs, new impellar) for less than 10 minutes (at two 5 minute intervals) the exhaust elbow reservoir became so hot that it melted the side of the remote control shift cable. Temperature reading was 150-160. I moved the cable so it wouldn't touch.

I plan to flush out the cooling system with 'Prestone flush' and then remove the heat exchanger and exhaust elbow reservoir for cleaning/inspection.

Question:
Do I insert a water hose into the the elbow reservoir and let it drain out of the heat exchanger while the engine is running? And for how long?

Thanks
-buc

 

[Eric 3.7LX Alpha 1]

Re: How to flush a Merc 470 cooling section

Post# 23 shows the engine cooling hoses and path it takes.

http://forums.iboats.com/showthread.php?t=390718&highlight=470+coolant+flow

Mr. Gasket sells a radiator cap that also has a built in thermostat on it. Can be used to verify the gauge you currently have. They come in different psi ratings to match what you have:

http://cgi.ebay.com/ebaymotors/THER...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

 

[Bt Doctur]

Re: How to flush a Merc 470 cooling section

Question:
Do I insert a water hose into the the elbow reservoir and let it drain out of the heat exchanger while the engine is running? And for how long?

I sure hope you dont.the exchanger can be drained by removing the drain plug at the rear.
block can be done using the block drain plug. If the elbow gets hot enough to melt the cable and your sure the impeller was installed properly then it`s time to replace the res/riser. AFTER YOU DRAIN THE MANIFOLD FIRST

 

[bucnon75]

Re: How to flush a Merc 470 cooling section

Great. Thanks for the info and the links.
I will just add the flush to the elbow, (not use a water hose), run the engine according to the instructions on the flush - and then drain at the block and the exchanger.

 

[mdlee]

Re: How to flush a Merc 470 cooling section

If you can... remove the frt cap on the heat exchanger.. U may find chunks of the old impeller. If you do find these chunks of ruber u will have to inspect each tube in the heat exchanger.. This might be some of your problam... Maby? These chunks can make there way into the riser,,, and cause hot water 2 back up into the system causing it to overheat..