Flushing raw water cooled engine

[tommyh]

I need to flush my 5411 universal.
Does the thermastat need to be removed also,I have the tee on my raw water intake. Does the other line need to be pinched off so it forces all the flush through the block.
I haven't decided what to use yet for the flush
The motor runs great and I am just doing this for maintenance reasons.
Thanks for any suggestions

[Wotname]

There is a semi recent thread about flushing raw water cooled engines.

I have just flushed my Yanmar 2GM20 and FWIW, here is some details.

I used 8 litres say 2 gallons of cheap white vingear recirculated though engines for 18 hours. I used a cheap bilge pump siting in a bucket. 18 hours because that was a convenient time frame!

I removed the annodes first just on principle.

I removed thermostat otherwise it would remain closed and thus not allow vingear though head and block. I blocked off the bypass hose that allows for the normal raw water to pass directly into exhaust injection point when thermostat is cold.

I'm not sure exactly how your engine is plumped but many (all?) rawwater cooled engines use the thermostat for two functions.
1. Block water to head and block when cold and divert water directly to exhaust injection point.
2. Allow water to head and block when hot and block the "by-pass" water going directly to exhaust injection point.

Providing you account for this cold bypass function, you should be right.

Initially I planned to use something stronger than vingear say HCl (say 20% for say 30 minutes) but I glad I didn't, even being careful, I managed to spill and spray the vingear around too much

[tommyh]

So the vinager works good for this?
I plan on just running it through the block and head by using a drill motor pumping through raw water inlet in block and out the crossover hose.
Or should i remove thermastat and push it all the way through exaust

[Wotname]

Originally Posted by tommyh

So the vinager works good for this?
I plan on just running it through the block and head by using a drill motor pumping through raw water inlet in block and out the crossover hose.
Or should i remove thermastat and push it all the way through exaust

The vingear worked well for me. It is a mild acid so needs a fair amonut of time to do its job. It was very very brown at the end.

I would push it though as far as possible but not INTO the exhaust.

[Russ]

Flushed my Yanmar with Hammer Head Descaler from Bright Bay it is one of the few things approved by Yanmar as the inside of the cooling tubes are Aluminum coated and dissolve with ANY acid. Not sure about vinegar. I circulated it for two hours and THEN took apart engine. CLEAN! In was at Raw Water intake, Out was a back of engine where hose goes to muffler. Both ends into a 5 gallon bucket using a garden foutnain pump. russ

[Wotname]

Russ makes a good point about fresh water cooled engine ( heat exchanger). I would be very careful about using any sort of acid including vingear without more research.

I have presumed it was a raw water cooled engine but I see I could well be wrong .

OP, is your Universal fresh or raw water cooled?

[PPLepew]

Yanmar engines are cooled by a fresh water loop. The thermostat directs that water directly to the engine or to the heat exchanger where the water is cooled by raw water circulating around the fresh water pipe, then back to engine.

Raw water is not involved in this loop. It gets in via through-hull, runs through heat exchanger (whether needed or not) and exists via exhaust. The thermostat is not involved in this raw circulation.

If you run with an approved antifreeze (even in summer) you should not have any sediments in the fresh water plumbing. I use clean filtered water (no calcium).

The problem with the heat exchanger is that the raw water sediments have the tendency to adhere on the "hot" fresh water pipe, slowly reducing the exchange. I could run all day at 2100 RPM, but only 15 minutes at 2200. Raw water circuit can be 'cleaned' by circulating vinegar (or diluted Muriatic acid aka HCI) for a while, until it comes out clean, using one of the pump suggestions above.

Depending on your engine location/access, the Yanmar bypassing of raw water pump and exhaust attachment is a bit of a challenge.

[tommyh]

It's raw water cooled
New head two years ago
Just wanting to add doing this to my maintenance schedule
i like the motor, works well for my 28,pushes it just fine in the bay.
Thinking about using barnical buster. Anyone ever used it?

[foothillsailor]

I did the same thing --flushing my raw water system with vinegar --did a good job.

THEN I thought why not leave the vinegar in the system for the 6-8 months while the boat was in storage during the summer in Mexico?

NOT A GOOD IDEA ---basically it really softened all the rubber parts (such as the impeller which looked good but was too soft/flexible to pump at high revolutions and also some tubing) ---so not recommended for long periods of time

[Wotname]

Originally Posted by PPLepew

Some Yanmar engines are cooled by a fresh water loop. The thermostat directs that water directly to the engine or to the heat exchanger where the water is cooled by raw water circulating around the fresh water pipe, then back to engine.

Raw water is not involved in this loop. It gets in via through-hull, runs through heat exchanger (whether needed or not) and exists via exhaust. The thermostat is not involved in this raw circulation.

If you run with an approved antifreeze (even in summer) you should not have any sediments in the fresh water plumbing. I use clean filtered water (no calcium).

The problem with the heat exchanger is that the raw water sediments have the tendency to adhere on the "hot" fresh water pipe, slowly reducing the exchange. I could run all day at 2100 RPM, but only 15 minutes at 2200. Raw water circuit can be 'cleaned' by circulating vinegar (or diluted Muriatic acid aka HCI) for a while, until it comes out clean, using one of the pump suggestions above.

Depending on your engine location/access, the Yanmar bypassing of raw water pump and exhaust attachment is a bit of a challenge.

There you go, I fixed it for you

Yanmar engines with the letter F in the model designator are fresh water cooled.

[PPLepew]

[QUOTE=Wotname;1888109]There you go, I fixed it for you Thanks

Yanmar engines with the letter F in the model designator are fresh water cooled. Hmm, I have a fresh water cooled 3YM30

[Wotname]

[QUOTE=PPLepew;1888387]

Originally Posted by Wotname

There you go, I fixed it for you Thanks

Yanmar engines with the letter F in the model designator are fresh water cooled. Hmm, I have a fresh water cooled 3YM30

Actually I should have said "most" rather than "some" and if one is only considering new Yanmar engines, it should be "almost all" IMO.

AFAIK, they only sell one raw water cooled engine these days - 1GM10, all to with emission requirements I believe.

I should have been more accurate and said "Yanmar engines with the letter F in the model designator are fresh water cooled however the lack of an F does not always denote raw water cooling"


For a far more detailed explanation see here ENGINE MODEL CODES