Mercruiser 6.2 Horizon FWC Antifreeze in oil

C

captk

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Joined
Jun 17, 2014
RO Number
33662
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3
Last fall I changed the oil on my engines and I sent out an oil sample to Blackstone Labs. The oil was 1 year old and had 22 hours on it. They reported once again antifreeze in the oil for the port motor and a now some in the starboard engine. The oil never looks milky, never goes higher on the dipstick and the engines run fine. I was trying to figure where to look for the possible intrusion. Any help would be appreciated. I was thinking risers just because they are at least 5 years old since I owned it and no idea about the previous owner. Just not sure where to start looking

Merc 6.2 Horizon FWC inboards

Port
1.16% Antifreeze (Anywhere from .41% to 1.6% since I owned it)

Stbd
0.28% Antifreeze (Always 0% till now)
 
Run in salt or fresh water?

The manifold/riser joint could very well be the source. A little AF leaking into the exhaust ports and getting into the combustion chambers can leak tiny amounts past the rings. The bad thing is the rings can rust to the cylinder walls and break on start-up. Doesn't sound like a lot of water gets into the exhaust ports, but it can also rust out the valves and seats. I've seen valves that look like swiss cheese.

If you want to check the risers, drain the AF down to a point lower than the manifolds to prevent splash to get down into the manifolds which will prevent an evaluation on the amount of AF getting down to the exhaust ports.

IF you are getting AF into the engine as I have described and not remedied, It's possible it will eventually destroy the engine.

This is only one scenario but part of the routine maintenance that should be investigated.
 
What Charlie said .

I expect the Blackstone report may have also mentioned slight head gasket leak as another possible cause of those results.
Besides possible compression and leak-down test, you might consider a combustion gas leak test of the A/F cooling system to see if you can detect traces of exhaust there.

Have you noticed any need to top up the coolant reservoir and can you smell any faint A/F odor in the exhaust ?

I have never tried it but apparently NAPA makes a test kit for that , part # 700 1006. If that interest you it would be a good idea to confirm it will work with your cooling system setup before purchase as I believe it is normally used with auto radiators.
 
Yup, Checking for exhaust gases getting into the anti-freeze is a very good idea. One I have completely forgotten about.
 
At those levels I would put a can of Bars Leak in both engines and forget about it until the next check.
 
That's great info. The boat has been around the Chesapeake it's whole life so anywhere from full salt up to fresh. The previous owner was much closer to the ocean so definitely salt water in it's history. I'll look at checking for the exhaust gases, the test kit looks pretty inexpensive. Either way risers are probably due or past due at this point. I'll update the post with my finding maybe next week.

Thanks,
Ken
 
BTW is Bars Leak safe in newer motors, especially Marine? I thought that used to have a history of clogging things up such as heat exchangers.
 
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