[lakesidevu]

My crusader 7.4 motor is losing antifreeze.

It is a 2001 all freshwater hours,less than 500.

This is my first season with this boat

No signs of any liquid in the oil,and no apparent leaks,no antifreeze in the bilge.

I'm not sure if the head gaskets would be a potential issue.

The motor runs fine at all RPM's

Any ideas on what to check?

Thanks for you ideas or feedback

[MC1600]

If you’re not seeing any leaks in the engine bay, my primary suspect would be a head gasket. Are you noticing any smoke when cruising? I suspect this would be hard to spot if you have underwater exhaust.

[jclark003]

heat exchanger is a another likely cause. when the head gasket fails you typically will see bubbles in the coolant tank when engine is running. make sure not to remove cap when engine is warm however. If oil is clean and no bubbles I would suspect the HEX. Or, not sure about your engine but on some, riser can also cause coolant leaks into exhaust.

[ReelMagic]

It could be the Heat Exchanger as mentioned by jclark003. On my 1997 31 open w/454 (previous Tiara) the heat exchanger failed allowing antifreeze to get into the salt water side when running.. The indication I had was the overflow antifreeze bottle located on the engine started to overflow as seawater was sucked into the cooling system when the engine cooled down.

[Matta0413]

Heat Exchanger. Take it off an have it tested.

[Donaldjames]

Are you overheating?

[cp4000]

I had a coolant leak and none of it ended up in the engine room or aft bilge on a 3300 open.  All the coolant ended up forward of the forward bilge pump under the cabin stairs.  Might want to send a shop vac down there and see if you can find some coolant in there.
Good luck!

[Lucky Dog 33]

I’d def start with the HEX. Without proper cleaning and inspecting, they will fail prematurely. Take it off and pressure test it. Do you know if they are original?

If it turns out to be the hex, make sure you flush the entire system before filling up with fresh coolant. As previously mentioned raw water can get sucked back into the system at cool down and you will have a mixture of old coolant and raw water, which will just cause future heating and/or corrosion issues.