How to drain the heat exchanger on a 8.1 horizon engine

[Gord]

Thinking ahead for next year, what is the best way to drain and flush a heat exchanger on a 8.1 horizon engine? I have a 2002 340 Sundance. One engine- heat exchanger is nice and clean the other one is dirty looking.
If I am cruising and then slow down, that engine will spike in temperature for a short while then go back down.

 

[tony1b2000]

The raw water drains itself when the engines are off.
I simply take each end cap off and flush with a hose! You will need 2 new gaskets. It takes 10 minutes to do this project.
Professionally, a radiator shop can boil them clean if you want to remove them.
That said, at least on my boat, raw water comes into the oil cooler first. That's where most of the debris will get stuck. Detach the both hoses to it or where they terminate and back flush with a hose. You will be surprised what comes out of there!

 

[Gord]

The raw water drains itself when the engines are off.
I simply take each end cap off and flush with a hose! You will need 2 new gaskets. It takes 10 minutes to do this project.
Professionally, a radiator shop can boil them clean if you want to remove them.
That said, at least on my boat, raw water comes into the oil cooler first. That's where most of the debris will get stuck. Detach the both hoses to it or where they terminate and back flush with a hose. You will be surprised what comes out of there!

 

[Gord]

The raw water drains itself when the engines are off.
I simply take each end cap off and flush with a hose! You will need 2 new gaskets. It takes 10 minutes to do this project.
Professionally, a radiator shop can boil them clean if you want to remove them.
That said, at least on my boat, raw water comes into the oil cooler first. That's where most of the debris will get stuck. Detach the both hoses to it or where they terminate and back flush with a hose. You will be surprised what comes out of there!

Ok thanks for the info. What about the antifreeze side of the heat exchanger. This is what looks like it needs to be cleaned

 

[dwna1a]

Ok thanks for the info. What about the antifreeze side of the heat exchanger. This is what looks like it needs to be cleaned

there is a drain on the underside on mine. That’s always a good time to change the zinc as well

 

[Gord]

there is a drain on the underside on mine. That’s always a good time to change the zinc as well

Ok I will lookup the zinc number. One more question. Do you know what kind of antifreeze goes in this?

 

[tony1b2000]

It does not have it's own antifreeze. It's the same from your engine that gets circulated from and to the engine to the heat exchange ger and back to the engine!

 

[Gord]

It does not have it's own antifreeze. It's the same from your engine that gets circulated from and to the engine to the heat exchange ger and back to the engine!

I do realize that but I would like to change all the antifreeze. One reservoir is dirty looking the other one looks clean

 

[R-and-R]

I do realize that but I would like to change all the antifreeze. One reservoir is dirty looking the other one looks clean

I would recommend removing the Exchanger and have a radiator shop boil it as another person said.

For coolant, I stick with genuine Mercruiser...
https://www.mercruiserparts.com/877770k1-anti-freeze

 

[Gord]

I would recommend removing the Exchanger and have a radiator shop boil it as another person said.

For coolant, I stick with genuine Mercruiser...
https://www.mercruiserparts.com/877770k1-anti-freeze

Ok thanks for the advise