another engine zinc question and associated antifreeze question

[Robin]

Our new boat has a Yanmar 3GM30F engine which is freshwater cooled. Should we change the engine zincs on this, is it necessary when not raw water cooled?

The boat is kept in the water year round in Florida so freezing risk is very infrequent to non-existent and even if there is a very rare frost the boat still sits in relatively warm water (currently 72F). SO should we need to replace the antifreeze mix in the freshwater system which is quite possibly past it's usual recommended change date ( P.O was hopeless and the engine only has 1200hrs on it so he most likely would have left it) Iam aware there are some corrosion inhibitors in the antifreeze mix, so is that a reason to drain and change on it's own??

 

[Tranona]

No anodes in that engine, so you can cross that job off the list. Would replace the coolant though.

 

[Robin]

No anodes in that engine, so you can cross that job off the list. Would replace the coolant though.

I asked because I thought I saw it mentione in the pages from the handbook the PO left on board, I hadn't actually seen them on the engine. However on our last UK boat with a 4JHE Yanmar, also freshwater cooled, there was at least one stud anode,(maybe on the heat exchanger??) not that it was ever changed by me or our PYC club engineer doing the annual service.

 

[nigelmercier]

I made some of my mates in the Canary Islands laugh when I told them I was buying antifreeze. They do sell it, but it is very weak on the ethylene glycol. There is probably more in a vodka in my local bar

 

[VicS]

Our new boat has a Yanmar 3GM30F engine which is freshwater cooled. Should we change the engine zincs on this, is it necessary when not raw water cooled?

The boat is kept in the water year round in Florida so freezing risk is very infrequent to non-existent and even if there is a very rare frost the boat still sits in relatively warm water (currently 72F). SO should we need to replace the antifreeze mix in the freshwater system which is quite possibly past it's usual recommended change date ( P.O was hopeless and the engine only has 1200hrs on it so he most likely would have left it) Iam aware there are some corrosion inhibitors in the antifreeze mix, so is that a reason to drain and change on it's own??

I asked because I thought I saw it mentione in the pages from the handbook the PO left on board, I hadn't actually seen them on the engine. However on our last UK boat with a 4JHE Yanmar, also freshwater cooled, there was at least one stud anode,(maybe on the heat exchanger??) not that it was ever changed by me or our PYC club engineer doing the annual service.

I made some of my mates in the Canary Islands laugh when I told them I was buying antifreeze. They do sell it, but it is very weak on the ethylene glycol. There is probably more in a vodka in my local bar

If there are anodes in the raw water side of the heat exchanger renew them as necessary to maintain corrosion protection in the same way as you would renew the anodes in a seawater cooled engine.

Antifreeze, or a summer coolant containing similar corrosion inhibitors, should be used in a freshwater cooled engined and changed at the appropriate intervals.

Cavitation erosion of cylinder liners (qv) is a problem in some engines ( Yanmars ??) The use of the correct inhibitors ( as in OAT antifreeze) is important to prevent this.

 

[vyv_cox]

If there are anodes in the raw water side of the heat exchanger renew them as necessary to maintain corrosion protection in the same way as you would renew the anodes in a seawater cooled engine.

Antifreeze, or a summer coolant containing similar corrosion inhibitors, should be used in a freshwater cooled engined and changed at the appropriate intervals.

Cavitation erosion of cylinder liners (qv) is a problem in some engines ( Yanmars ??) The use of the correct inhibitors ( as in OAT antifreeze) is important to prevent this.

No engine anodes in my Yanmar GM30F.

Vic is correct about the corrosion inhibiting properties of antifreeze, an important aspect of the mix.

Cavitation erosion on the water side can be a major problem in wet liner engines, although usually bigger ones than we typically see. This one is from a large diesel engine but I have also seen examples from gas engines. The cause is often using water only in hot climates where freezing does not occur.

 

[Robin]

Now I am worried. Is it enough to drain off say 25% of the freshwater side and top up with new stuff or does it need to be a totaldump and refill? After two new hips and a stroke, I don't do the engineroom crawl as well as I used to and mopping up gets cramps everywhere, but the alternative charges $85/hour!

 

[vyv_cox]

Perfectly OK to add antifreeze as you suggest. Two minutes of running the engine will mix it thoroughly.