heat exchanger

Discussion in 'Boats and Motors' started by dexterm16, Nov 20, 2008.

  1. the heat exchanger on my '86 170 i/o chaparral has 2 screw in plugs near the rear of the unit. can anyone tell me what the first one(closest to the front on motor and boat) is and what the second one( back of boat one) is?
  2. there drain plugs...I beleive the front one is for the anti freeze that stays in your motor and the back one is raw water...if you cant get them off make sure to take the small hoses off and fill with rv anti freeze or you'll be buying a new one (over $400) in the spring

  3. On my Mercruiser 470 the rear drain plug is for sea water. The plug nearest the front of the boat is to drain the anti -freeze in the closed part of the system. Do one of them and you will be certain for your boat. I would think all Merc. equiment would be same. If you drain the sea (lake water) from the heat exchanger there is no need to add anti freeze. There might be one or two other drain points for sea water on your engine depending on your model. Best to purchase a manual to be sure. It is much cheaper than guessing. It is a good idea to remove the heat exchanger every year or two and inspect and clean it. Be careful not to overtighten the end caps. They will crack quite easily.
    Tip -Be sure to put lower unit in down position to allow water drainage. This also prevents "sets" from forming in the hoses and belows over the winter.

    PS: I would not wait much longer than today.
  4. thanks.i figured this much but wanted to verify what i thought.