Gear Oil Cooler Zinc

[James Freeman]

My 2010 QSB 5.9 gear oil cooler did not have sacrificial zincs. My friends 6.7 engine did and until he started fresh water flushing he ate the little zincs constantly and found all manner of zinc debris on intake side of cooler.

Recently at 9 years I proactively replaced my gear oil cooler with a model that had options for 2 zincs one at either end. I had never had an issue with cooler and it was always clean as I fresh water flush but I was worried about a wear breakdown of the metal tubes with time allowing a seawater gear oil mix. On my new cooler I plugged the intake side as I didn’t want to block water flow with any zinc debris but left the output side installed.

I really wonder if I actually need a zinc in the gear oil cooler on the QSB 5.9. At rest most water drains back to bottom of after cooler on shutdown I believe. If I frequently flush is there more of an issue of sending zinc fragments downstream from my gear oil cooler to the intake side of the heat exchanger causing potential issues?

Topic

[Tony Athens]

I vote to use zincs

[James Freeman]

New Version Zinc Cooler QSB 5.9

This is an interesting subject- no zinc wear on the Seaboard sourced Sen-Dure version to speak of. I fresh water flush and the unit was still very clean at 2 years. I did remove and plug the intake zinc to avoid any blockage from zinc particles. I know a friend who had a lot of trouble with that intake side zinc on his OEM 6.7 cooler which also had the zincs on the bottom-what a mess to service. Since I went 9 years on the OEM no zinc version which had not failed I thought I would try this out. I do note that since replacement in Spring of 2020, COVID cruising has kept us in home waters and we have had no long cruises with multiple long cruising days. I will watch closely as we hopefully head to Alaska this summer. <br /><br />I plan to pressure test it at 4 years when I next remove the After Cooler on its 2 year cycle. Not looking forward to removing it as it is a bit hard to reach. Also the strap mount is difficult to attach compared to the OEM version with the triangular plate. 

[Rick Pilling]

Gear oil zinc

Jim,

How is the erosion on your gear oil cooler zincs?  Have you serviced the core yet?  Any opinions on using one zinc?

Rick

[James Freeman]

Thanks for Replies

Thanks for the replies folks- staying with the single zinc in the cooler. Will know more about my theory when I overhaul heat exchanger next spring.

[Rob Schepis]

Bill,
No, use the zincs as interconnected metals bonded together are protected properly when they are in the same water bath such as hull zincs, seacocks, etc. The engine coolers are often sitting in their own seawater bath.

[Bill]

Related question. My replacement gear oil coolers came with two zincs and a bonding wire post. I went ahead and bonded it to the engine block. Can I forget about the zincs as a result?

[Tony Athens]

IMO, use the zincs.. If you really fresh water flush when are the dock, I’d still use one zinc.

[Author]

Replies