raw cooling water conversion

[sawingknots]

i've been toying with the idea of converting the raw water coolent system on my old yanmar to a fresh water one,my idea is to keep using the exisiting pump to cool a heat exchanger then directly on to the exhaust elbow,the engine coolent water would be cooled at the exchanger then circulated throughout the engine utilizing a small storage/overflow tank,my question is wouldn't i need to install a second additional pump to circulate the fresh water?i have saw a few engines[nonmarine]that don't have a water coolent pump but use some-kindof heated water ambient circulation,what do you think do i need the second pump?

[Paul_L]

Why change at this age? Seems like a freshwater cooled engine is likely to last longer and run a little more efficiently, but after a lot of years, I can't see that it would make any difference. If you aren't going to use Yanmar parts, you can still look at the cooling diagram for the freshwater cooled version of your engine.

[Faster]

If you're sure that the engine is not already compromised by corrosion then this may be a good idea. You will need a second pump for the RW circuit.. usually belt driven off the engine as an aftermarket thing. There are a couple of outfits in the Bellingham/Seattle area that I know of that make tidy little heat exchangers for retrofit.. a bit of googling should turn them up.

[RichH]

The pump that is needed for the fresh water circuit must be able to withstand higher than 180°F temperature .... this requiring the avoidance of most 'rubber' etc compounds which 'soften' when above 180°F, etc. A 'fresh water' pump in a heat exchanged cooling system is best served by a pump with a METAL impeller although there are some 'rubbers' that can be used at near 'boiling water' temperatures.

Its never too late to 'convert' a raw water cooled engine to 'fresh water' cooling as the "life extension" of the engine by lessening internal corrosion will be significant, especially in the case of the raw water being 'salt water'.

good sources for such 'conversions' to FWC Heat Exchange systems are: Atomic 4 - Indigo Electronics, Inc. and Moyer Marine Atomic 4 Engine Rebuilding and Parts .... they both offer fresh water 'conversion packages' and components for Atomic-4s and SMALL diesel engines.

[sawingknots]

[QUOTE=RichH;793335]The pump that is needed for the fresh water circuit must be able to withstand higher than 180°F temperature ....
yup your exactly right rich,that hadn't even occured to me!i rebuilt this engine about 4 yrs ago and its only been in fresh water pretty much ever since,my main concern is forgeting to drain before a hard freeze and then again"if it ain't broke don't fix it?

[RichH]

NEVER 'dry out' a cast iron engine for long term storage !!!!!!!!! Always FILL it with AF with rust inhibiters.

'Draining/Drying' an engine will 'accelerate' the formation of destructive RED rust and destroy the already formed protective BLACK rust that forms on Cast iron. Anti-Freeze with rust inhibitors will help keep the BLACK (ferrous) rust intact and 'slow' the transformation of it into destructive RED (ferric) rust.

[casey1999]

I was considering switching my Yanmar 3gmd (30 yrs old) to freshwater, but the cost and adding another water pump/belt (that can break) steered me away. Instead I installed a hose on the water intake that I can attach a bucket, fill the bucket with water and do a fresh water flush at the dock after using the boat. Maybe I will get another 30 years this way. Your situation is a little different (your concern is freezing).

[JimsCAL]

Here is Indigo's system which they market as suitable for small diesels. Note it uses the existing raw water pump to circulating the fresh water/antifreeze and the new electric pump as the new sea water pump.

Atomic 4 Fresh Water Cooling System - Electric Antifreeze Pump

[sawingknots]

thanks jim,i'll look into that btw this is not a high priority for me ,just something that keeps occuring to me at times

[sawingknots]

Thermo-syphon Water Cooling System (Automobile) ah yes this the idea i was refering to,i probablely won't try it but if set up right i'm pretty sure it would work