Need help with how to find antifreeze leaks?

[Marauder 28 twin]

Hey Everyone,
I have Twin "88" 3.7LX Mercruisers with 378 hours on them and the last 2 times I went out to the Islands (Anacapa) I've had antifreeze in my hull and starboard motor about a gallon low and port maybe a qt. I went home last trip and filled them up and ran them for about an hour at 2500-3000 RPM and could not see any leaks, and before I went out Friday I checked and they were full. When I got out to the Islands and while fishing I ckecked them and Starboard motor was 1/2 gallon low. I added it and headed back. before getting to the harbor I noticed the temp was rising so shut it down so I would not over heat it, I know these motors don't like to be over heated due to the Aluminum block and steel head. and when I got home it was a gallon low again? with Antifreeze in my hull. I hooked them up and ran them while flushing them out and can't see any leaks.
Is there someone out there that knows these motors and can give me some clues on where to look?
I would deeply appreciate it.

Thanks for your time!!

Marauder 28 Twin

 

[fat fanny]

Re: Need help with how to find antifreeze leaks?

I would run near shore and have someone @ the helm while u scower the the engine compartment with a mirror and flashlight if need be all around the manifolds, circulating pumps and hoses things to look for are pin holes,leaking gaskets and casting cracks make sure your crank case fluid level isn't getting any higher watch for oil trails behind the rig as well but mainly concetrate on the above items most likely will only be seen under load of both engines. Good luck!

 

[Eric 3.7LX Alpha 1]

Re: Need help with how to find antifreeze leaks?

The only places I've leaked coolant from were the dreaded weep hole from the cam seals worn... and a bad radiator cap which would leak only a little bit and evaporate almost immediately, but I did see it and replaced.

 

[achris]

Re: Need help with how to find antifreeze leaks?

Could also be the exhaust elbow gasket. How long since the elbow was inspected (and the gasket renewed)?

Chris......

 

[Marauder 28 twin]

Re: Need help with how to find antifreeze leaks?

I would run near shore and have someone @ the helm while u scower the the engine compartment with a mirror and flashlight if need be all around the manifolds, circulating pumps and hoses things to look for are pin holes,leaking gaskets and casting cracks make sure your crank case fluid level isn't getting any higher watch for oil trails behind the rig as well but mainly concetrate on the above items most likely will only be seen under load of both engines. Good luck!

This sounds like I need to do, Thanks for your input I'll let you know what I find.
Marauder 28 Twin

 

[HT32BSX115]

Re: Need help with how to find antifreeze leaks?

This sounds like I need to do, Thanks for your input I'll let you know what I find.
Marauder 28 Twin

You really need to pay close attention to what Chris said above.

If you have an internal leak in the exhaust elbow (riser) gasket, you can dump your coolant overboard out through the riser along with the raw water cooling the riser and never see it.

You can easily hook both cooling systems up to a compressor and pressurize them to rated pressure. (DON'T exceed the rated pressure of the cap)



Get a UV type leak detector like the "Mastercool 53351 Professional UV Leak Detector Kit or similar". (about $50)

If it's leaking into the engine compartment, you'll find it.

Overheat the "dreaded" 470/3.7L engine, and you're right, You'll be "sorry"!


Good luck,


Rick

 

[stonyloam]

Re: Need help with how to find antifreeze leaks?

The only places I've leaked coolant from were the dreaded weep hole from the cam seals worn... and a bad radiator cap which would leak only a little bit and evaporate almost immediately, but I did see it and replaced.

+1 While the engine is hot and running, look at the lower starboard side of the engine waterpump to see if antifreeze is leaking out. It will only leak when it is running and hot enough to build some cooling system pressure. You should also do a cooling system pressure check, and a compression check while you are at it. Borrow the tools free from autozone. Good luck.