Anyone hear of Mercruiser 496 intake manifold problems?

[mnm99]

I know all about the Aluminum exhaust manifold problems. I was told from a mechanic to watch out for the intake manifold problems the 496 has...Huh?? He said because of the high flow of the water pump the manifold acts like a high pressure washer and can wear away at the aluminum, create pin holes and cause antifreeze to go into the oil. Any Idea what he is talking about?

 

[yv1]

The intake manifold is cooled by antifreeze coolant on closed 496. If for any reason you get coolant into your oil, you will have low coolant and too much oil. Oil level and coolant level should be check before every run. You should be able to catch this problem before any mayor damage to the engine.
I've never heard about something like this on any type of engine. I think the mechanic is mixing the initial problem on aluminium exhaust manifolds with rust on on the closed side of cooling due to old acid coolant. You should change your coolant every 5 years or so.

 

[mnm99]

Yes I check my fluid pretty often. I never heard about the intake problem also. Something about the coolant passage being small and acting like a power washer at high rpm..Who knows. I changed my coolant to the 5 year stuff last year. I'll keep an eye on it.

 

[yv1]

Oil analysis is good thing to do every other year. It will tell a lot about your engines.

 

[Spark600]

I do oil analysis every year the best $ 25.00 ever spent. When I sell the boat I will have oil reports for all the years that I owned the boat with maintenance records there will be no questions about the motors at all.
On my previous boat after doing the oil samples for three year with no problems, The fourth year report said very small traces of antifreeze in the oil must due oil sample next year so they can compare it to all previous reports to see if antifreeze is still in the oil, possible head gasket going bad.

 

[mnm99]

Where do you guys send out the samples too? I'd do that now and also take a look for the heck of it at the end of the season. For $25 its a no brainer.

 

[Spark600]

I use Blackstone lab 260-744-2380 or blackstone-lab.com
Attached is my report from 2017 oil change