I would look at the heat exchanger first... I don't think that there is any antifreeze circulating through the manifold, only raw sea water.

 

i believe he is right. the antifreeze just cools the block and heads. the raw water cools the heat exchangers and the manifolds. check the heat exchangers.
sherman

 

Thanks, KaGee. I couldn't figure out a good way to check the heat exchanger so I ordered a new one. I'll let you know how it goes. Its killing me to miss the walleye bite out of Lorain lately!!

 

I will be the first to say that I have absolutely no clue about the Mercruiser 170 or any other inboard... LOL

But as a gearhead and builder of HP street engines, coolant from the exhaust is a sure sign of head gasket failure.

 

I have to agree with Dan#####, Aluminum block steel heads? Get a Cooling system pressure tester at a parts store, closed cooling on a boat is almost the same as a car. except it is cooled with water through the heat exchanger instead if air through a radiator.
Buying a new heat exchanger in a guess sounds $$$$. they can also be pressure tested with a tire pump and a couple of hose fittings. Good luck Bill

 

I had the same problem on my closed cooling system. Your heat exchanger is not the problem if antifreeze is leaking out of the exhaust. You have a leak in the engine. Pull your plugs and see what they look like. If the heat exchanger was bad, you would be pumping the antifreeze overboard with the lake cooling water discharge.

 

If the heat exchanger was bad, you would be pumping the antifreeze overboard with the lake cooling water discharge.

Would still drain out the exhaust, no?

 

Possibly a cracked head. Anything getting into your oil ? Mike

 

The problem was a crack in the heat exchanger allowing the antifreeze to mix with the raw water and get pumped out the exhaust with the raw water. Replaced the heat exchanger (found new one for $500) and problem cleared up. The coolant was leaking into the heat exchanger when the boat wasn't even running, then would completely empty within 15 minutes at idle. That told me it probably wasn't a cracked head or gasket, just leaking too much too fast. Also the coolant ran out the exhaust (just have a thru hull hose instead of the bellow being attached to the outdrive) as opposed to "spitting out" which told me it probably wasn't the exhaust manifold.

Hope this helps someone else who may have the same symptoms!

 

Also, oil was clean.

 

By exhaust you meant where the water comes out? I thought you were talking about where the engine exhaust comes out lol


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By exhaust you meant where the water comes out? I thought you were talking about where the engine exhaust comes out lol


OutdoorHub Mobile, the information engine of the outdoors.

Engine is an I/O, not an outboard.

 

Glad ya found the problem, need to get fishin, wouldn't want ya to miss the 94 degree days now would we !! Glad to hear you found the problem, could have been alot worse. Mike