Where did my antifreeze go?

Hello,

New to the this forum but have read some of the posts and articles here over the years. I have been around boats my entire life and have had a couple Malibu's, a Mastercraft, and I currently found my self going back to my roots with a 2007 SN 196 (couldn't be happier!) I have always performed all of the maintenance on my boats and feel very comfortable working around them. This fall after I winterized my block i noticed i was getting a small amount of antifreeze in the bottom of the bilge. I figured it was just some residual from the winterization process so I wiped it up and the bilge was dry. Few days later there was antifreeze in the bilge again. I wiped it up again and checked every hose, elbow, freeze plug, connection, etc that I could think of.   I placed several new shop towels down in the bilge and checked the next day only to find a small amount in the bilge again. It almost seemed like it was coming from an area where the transmission bolts up to the block but I couldn't get a mirror or anything to see down in there. This spring when I pulled the boat from storage I pulled out one of the knock sensors and only got a few drips of antifreeze out. It appears most of it had drained out over the winter and ran out the drain plug. Note that when I winterize i drain the complete block, hoses, elbows, manifolds, etc, and leave the port and starboard knock sensors out while I pour in antifreeze through the thermostat housing. Once i see antifeeze come out of the block on each side I put the knock sensors back in and add another 1/2 gallon or so. I also add antifreeze to elbows, manifolds, etc and I'm very confident I have properly laid up the engine block. We put almost 100hrs on the PCM 330 Excalibur last summer and I never noticed any water in the bilge other than a very small amount from the packing gland. Any ideas where my antifreeze leak is coming from? Is there reason for concern?
I'm stumped!

Thanks!

Was thinking the trans cooler also however I don't think that much or any fluid would get past the impeller so that does not explain the block drain. Does the boat have a heater or shower? If so be sure shower head is off and heater core is ok. Draining down to that low block plug/knock sensor is weird.

I would clean the bilge completely and lay paper towels down to isolate where the drip is occurring.

Thanks for the quick feedback. Trans cooler was drained and properly winterized. No heater or shower to worry about. And both banks were almost empty. Last fall I did the dry paper towel test after cleaning out the bilge completely. The leak "appeared" to originate back where the transmission bolts up, but again I couldn't verify exactly where it was coming from. Boat is dewinterized and waiting for a break in the weather to get back on the water. Just a little nervous that i never found the problem.

I guess it should also be noted that it was a very slow leak.

Considering this is a raw water cooled motor the title is a little deceiving, you are leaking whatever coolant is running through or residing in the motor, are you seeing water gathering in the bilge after using the boat??

Which would lead one to believe there is no leak?? Is it possible the a/f you are seeing is residual drips from your backfill process of over pouring?? If there is no sign of water in the bilge or high running temps during normal use I would change up my backfill method next fall, keep the block plugs/knock sensors in and backfill using the same amount of a/f as you typically add.

Here's a picture stolen from the internet of their location. They may be a little high up to cause your engine to be drained like you experienced but if you run it and look for leaks, like I said in the previous post you should find something somewhere



And by the way Pete, no need to jump in and call them core plugs or tell why they're really there

Sounds like a plan

quinner wrote: Ken, You know what I want to say about your reference to the round things you described, lmao!!

What round things?

Just a thought... I was getting a small amount of antifreeze in the bilge of my 2006 216 over the winter for two years in a row. I checked everything. I also noticed a small amount of water in the bilge after use in the summer. I am very anal about my boat and even have fashioned a small plastic bowl under the snuffing box to catch the drips to keep my bilge dry. The antifreeze and water was leaking from a small hole in the bottom of the muffler. The hole wore through from rubbing on the hull. Easy repair but a pain to get the muffler out. Just a thought...

James, I'm the same way about my boat. Meticulous about everything all while putting as many hours as possible on the water during the season. I'll take a peak in that area as well. I checked all the hose clamps on the exhaust but didn't think about a pin hole in the housing. Thanks for the feedback.

Don't feel like the Lone Ranger on the CRAP weather. It's been cold rainy and record high water on our little lake as well. Oh and I forgot to mention windy!

James - you mentioned a hole in the bottom of your muffler that was repaired. I recently changed my oil and noticed a significant amount of water in the bilge while the engine was running. I discovered a hole in the bottom of my muffler, about an inch long. Curious as to how you fixed yours. I would prefer to do that rather than replace the entire muffler obviously. Anyone else who has experience with muffler repairs feel free to chime in. Thank you!