I have 2006 270 SLX with a Mercruiser...

[CWW]

I have 2006 270 SLX with a Mercruiser 496 Bravo 3.   Recently I've had to start adding coolant to the overflow reservoir before each use.  Nothing is leaking into the bilge so I'm assuming that it is going out with the raw water.   Any ideas of where to start looking for the leak?

[Bald_Wizard]

I would check the heat exchanger first. That is the cylindrical tube mounted on the front of the engine. Very likely the cause of your issue due to the fact that raw sea water is very corrosive and due to the age of our boats id bet this is where your coolant is escaping

[Jaay757]

Yes prob the heat exchanger.

[joe1]

My issue turnes out to be bad radiator cap

[Bald_Wizard]

Well that is great news! That’s a lot cheaper than a heat exchanger!

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[lance]

Start with the heat exchanger

[CWW]

Turns out it was the heat exchanger as most of you suspected. I'm back up and running.... After a $2,000 bill