Overheating Mercruiser

[cobrak69]

I just bought a 19' Stingray powered by the inboard outboard Mercruiser 190. Upon checking fluids prior to the maden voyage it was descovered to be about a galon low on coolant, my friend the genius decided to just put in plain water instead of a 50/50 antifreeze mix. I didn't know this until much later. I took the boat out an noticed it was spitting slowly out of the over flow tank white milky water. about an hour later the boat started to run hot, 200 plus so I shut it down waited until it cooled enough to pop the cap and refilled it with river water since that was all available at the time. And limped it back to the boat launch after only over heating one more time on the way back. I do not know if the mixture is what caused the over heating or if it is from something else. I was hoping someone on here may have some ideas. I also noticed a goot amount of white water in the engine compartment area every time I switched the bilge pump on it had a galon or so to kick out. There is no water in the oil according to the dip stick so I am a little lost here. Please advise

 

[Laddies]

Re: Overheating Mercruiser

Sounds like a blown head gasket, let the engine cool then refill the engine with coolant ( might just as well use water for the trouble shooting) with the coolant cap removed start the engine and let it run if it blows bubbles in the coolant you have a blown headgasket

 

[MrBill]

Re: Overheating Mercruiser

"69"...you don't indicate the type of engine, but I'm assuming the 3.7L because of two references, '190' and the closed cooling system. There could be several issues and you'll need to go through some diagnostics.<br /><br />First the over heating.. could be worn impeller (in the lower unit) causing inadequate raw water flow, obstruction in cooling passages (particularly heat exchanger), the thermostat or an issue allowing escape of coolant, such as head gasket mentioned by Laddies.<br /><br />Since your coolant is discolored, start by pressure testing the closed side of the cooling system. You might not be able to locate where a leak is, but you'll find out if there's a loss of pressure. If you fail the pressure test, the problem could be the head gasket, cracked head, cracked block, etc. Your climate probably would not suggest freezing to be the culprit if your pal filled your coolant resevoir before winter. <br /><br />If you pass the pressure test, check the thermostat, then the raw water side of the closed systms, checking for obstruction in the heat exchanger and other areas, like the riser.<br /><br />Providing addtional info, ie. engine, year, etc. will allow better responses and more feedback.

 

[Bondo]

Re: Overheating Mercruiser

You're running 2 threads about the Same Issue.........<br /><br />This is a C&P of My post on your Other Thread......<br /><br /><br />"I Hate to be the 1 to tell You,.........<br /><br />But,... You've got a Very Sick Old 470,........ It Needs Professional Attention,.. Immediately......<br /><br />If You're going to attempt the Repair,... A Mercruiser Factory Manual for that motor is a MUST.......<br /><br />Good Luck......."

 

[cobrak69]

Re: Overheating Mercruiser

This is a 1986 Mercruiser 190 I assume the 3.7. I have not tested anything yet, but am also having a problem with puffing oil through the valve cover breather as noted by "Bondo" in another post. I have great knowledge of car engines and rebuilds, but heat exchangers and marine applications are a little scethcy to me, which is why I am asking for advise from those who have been there and understand this engine. I would sooner set the boat on fire and watch it burn to the ground than pay the dealers price for repairs and take my chances of screwed as they usually do around here.

 

[Don S]

Re: Overheating Mercruiser

The 3.7L engine is nothing like any car engine. It's a 4 cylinder aluminum mistake Mercruiser made that had a Ford 460 head on it. Had lots of problems, and leaks on the cam/water pump seal. Plus other cooling problems in the early days.<br />Basically, like Bondo says, if you want to work on it, get the Merc manual or you will never get it fixed.<br /> Merc Manuals