Coolant in bilge???
 

Ok, got in the boat to change oil Saturday and noticed a little coolant under the port engine plus it looks like some must have got on the belt because there was a little splatter on the firewall. Still coolant in the resevoir but its low. Cleaned it up and let the engine run for a little while and no new leaks. Any idea's where this is coming from? Leaking hose or bad water pump maybe? '04 Model 496 mags with 130 hours.

Try to pressure test the system.

My '04 496 Mag does this every winter. Something shrinks up in the cold and she leaks a little coolant into the bilge. Every spring I clean it up and it does not leak during the boating season.

This type coolant leak on the 496 comes from the two seals on the bottom of the heat exchanger tank on the front of the engine where it pushes into the crossover manifold it sits on. Cleanup the leaks, refill the coolant bottle to correct level and run the boat. If the leak (drip) stops, enjoy the season, if it does not then order two new seals from Mercury, remove the tank and change these two push in seals. Not a seripous problem, happens on a lot of 496's in storage from temp changes.

Best Regards,
Ray @ Raylar

Thanks guys, hopefully thats the case. Was worried I was going to end up in a bind the day before the Tickfaw 200.

Ray, did Merc also state at one time that the 2 stainless hose clamps holding the exchanger in place might have been installed too tight also contributing to the leak? Or did I just dream this up?!

I changed the seals on the port one 2 years ago...

moved my boat the other day to get another out and guess what?

puddle of coolant on the floor...

wonder which side leaked down?

I'll find out next week when I get in to do some commissioning!

How to stop a 496 closed cooling tank from leaking or dripping
 

We install the tank in the seals with the seals and flanges dry as a bone, clean!, no oil, coolant or slippery. Make sure the thermostat flange (black aluminum) is in with the correct side up and the "front" mark facing front and the undertank bypass rubber hose coupler installed correctly with the angled edge facing up and back and that clamp tightened properly.
We crank the stainless clamps down just tight enough not to start crushing or denting the tank wall and we never see leaks again. Just our expierence and two cents kick'in in!

When you do your winter storage, loosen the cap on the coolant recovery bottle so not to create a vacuum on the system as the temperatures drop and the coolant and air in the closed cooling system shrinks!

Hope this helps with some struggling here.

Best Regards,
Ray @ Raylar

Is there a certain type of coolant to use? From auto parts store or Merc? thks!

Mercruiser 496's are sold and delivered with Dex-cool or equal as the coolant of choice by Mercury and as such I think thats the best coolant to continue using.

Regards,
Ray @ Raylar