open to closed loop conversion?

[ghettoyacht]

I have a 1991 mercruiser 350 alpha drive in my rinker cuddy. I occasionally use this in saltwater, but mostly on lake norman in north carolina.

I would like to convert this to a closed loop system if feasible. is there a kit for this? schematics? Also should i be using a 140 degree thermostat for open system or would a different temp be more efficient and better for my engine? would there be a different temp stat for a closed loop system? thanks for looking!

 

[45Auto]

Re: open to closed loop conversion?

It's possible, and there are several kits out there for it. Your problem is that it's not advised on engines that aren't almost brand new, and especially not if they've been used in salt water. Scale builds up internally in the engine cooling passages over time, and there's no way to clean it out. It will clog the internal passages of the heat exchanger if you add closed loop cooling. Your 19 year old engine is garuanteed to have plenty of scale in it. There's also no way to clean the internal passages of the heat exchanger, they clog up from the scale in your engine then your engine overheats and dies.

 

[jtybt]

Re: open to closed loop conversion?

Yeah, not recommended on an older engine...especially if it's seen salt water. salt can build up in the casting and rust pores too that react with anti-freeze.

There are ways to clean the block but not sure if it's worth your effort without knowing the condition of the block.

 

[HT32BSX115]

Re: open to closed loop conversion?

Howdy,

I did it on my 1997 454 (120 hrs since new) fresh water engine.

The engine was sitting on a stand with the intake manifold and recirculating pump removed. I removed all the core (soft) plugs and flushed it EXTENSIVELY. With the core plugs and water pump removed, I could see fairly well into the water jacket and could actually see pretty well around the cyls.


There was a fair amount of debris (sand, rust, etc) removed during the flushing and when I finished and installed the system, I filled it with 50/50 Dexcool.

It's been running for about 3 years now and I would not go back to a raw water cooled system.

I bought my closed system from http://www.oceaneastmarine.com/

It was easy to install, not all that expensive and you can buy the systems from many places including right here on iBoats probably.


On a 20 year old block however, I would probably NOT install one unless I could do a complete rebuild. I would want to acid flush the cooling passages in the block to ensure that all the surface rust was removed and of course I would replace the intake and exhaust manifolds and risers etc.

It's very hard to un-plug a heat exchanger that is clogged with rust flakes.

Now having said that, if you did a complete rebuild, you'd be money ahead to replace the engine with a long block engine so that you would have a known (clean) cooling system.



Regards,


Rick