mercruiser 5.7 fresh watter cooling

[jabfd]

Hi All,

Happy new years eve !! just thinking of upgrading to fresh water cooling on my 2002 Mercuiser 5.7 L it has under 400 hours on it. Is it worth to install a new fwc kit (MFH 5320b) at this point ? just trying to figure out how much longevity this would add to the engine or is the damage already done at this point. thanks in advance

 

[Bondo]

Is it worth to install a new fwc kit (MFH 5320b) at this point ?

Nope,...... Do it if or when you replace the motor,......

 

[alldodge]

Agree, and if your in fresh water then no need

 

[Scott Danforth]

Hi All,

Happy new years eve !! just thinking of upgrading to fresh water cooling on my 2002 Mercuiser 5.7 L it has under 400 hours on it. Is it worth to install a new fwc kit (MFH 5320b) at this point ? just trying to figure out how much longevity this would add to the engine or is the damage already done at this point. thanks in advance

the damage was done in the first few hours. you put a heat exchanger on new engines.

if you boat in fresh water, the block and heads will last decades
if you boat in salt water, your long over-due for manifolds.

 

[Lou C]

Even in salt water the block & heads will last 15 years. Manifolds and elbows, 5-7 years to be on the safe side.

 

[tpenfield]

I added 'fresh water' cooling (aka "Closed Cooling") to my Mercruiser engines @ 740 hours with good results

A few words of caution . . .

1) If the engine have seen salt water at all, then it may not be a good thing to do. TOO MUCH RUST SCALE will be inside the engine block, which will eventually clog the heat exchanger. :facepalm: . If your engines have only seen fresh water for their entire life, then the rust inside the engine block will be more 'powdery' and can be 'managed'.

2) Do a cooling system flush (similar to an automotive radiator flush) before adding a closed cooling system kit. As an additional measure to eliminate rust withing the engine block, you can do a cooling system soak & flush with 'oxalic acid' solution (aka wood bleach), then a baking soda solution flush to neutralize the acid.

3) I'd recommend a FULL closed cooling system kit (engine block + exhaust manifolds)

4) Inspect the exhaust manifolds and riser/elbows before doing the conversion kit. It may be beneficial to replacing them at this point and starting fresh with the closed cooling system.

5) Just be aware - Some full closed cooling system kits do not provide sufficient 'by-pass' at the thermostat to allow some cooling of the exhaust manifolds during the engine's warm-up stage. If you get some funky temperature cycling on your temperature gauge, you may have to do a minor modification to the thermostat to allow for more 'by-pass' before it reaches its activation temperature range.

If your engine's history is positive, then you could convert to closed cooling. Otherwise, you are best to start with a fresh engine block, etc.

 

[jabfd]

thanks for all the replies the engine has been used in salt water in cape cod with the po and now with me in salt and brackish water. so I think I will wait until I need to repower.