We have a 1993 33.5 with a Yanmar 3GM30F engine. I'm in the process of winterizing the boat and want to do a complete change of coolant/antifreeze. I was wondering anyone has ever used an automotive flushing kit that I could put into the hose that feeds the hot water tank with the hope of flushing all the old coolant out of that part of the system. Other option is to unhook the hoses at the engine and blow the hoses out of with air pressure. Thoughts?
Coolant flush
- Thread starter Sutric
- Start date
Do you have one (maybe 2) of this type of fitting anywhere along the heater water lines? My 3GM30F has 2. One at the top of the engine and another near the water heater input hose behind the heater itself.
This would be your flush out connectors to do what you are asking.
They allow you to attach a garden hose to flush the system and only remove one hose to allow the flush out to be drained into bucket.
That’s how I did mine a while back.
Also, on either side of the engine are small petcocks. They may or may not have a clear pvc hose attached to them. The engine heat causes them to dry rot and fall away, but the petcocks are there.
Spray them with a little PB Blaster or the like to make certain they are free before just trying to open them. If nothing comes out after opening them up, use a thin wire to scrap around the opening to free any crusted up gunk inside the opening. These allow you to fully drain out the antifreeze.
Just add a length of tubing to each so you can drain each side into a soda bottle.
It‘s a time consuming job but a pretty straight forward process.
Hope this helps.
This would be your flush out connectors to do what you are asking.
They allow you to attach a garden hose to flush the system and only remove one hose to allow the flush out to be drained into bucket.
That’s how I did mine a while back.
Also, on either side of the engine are small petcocks. They may or may not have a clear pvc hose attached to them. The engine heat causes them to dry rot and fall away, but the petcocks are there.
Spray them with a little PB Blaster or the like to make certain they are free before just trying to open them. If nothing comes out after opening them up, use a thin wire to scrap around the opening to free any crusted up gunk inside the opening. These allow you to fully drain out the antifreeze.
Just add a length of tubing to each so you can drain each side into a soda bottle.
It‘s a time consuming job but a pretty straight forward process.
Hope this helps.
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If you are just trying to get the coolant out of the heater loop, we used a cheap liquid transfer pump (https://www.autozone.com/test-scan-...p/p/performance-tool-transfer-pump/500025_0_0) which has a 48" thin plastic hose. After draining the block, we removed one heater hose from the engine, put the pump's tube down that hose and pumped the coolant out. I guess I can't be sure it got everything out.
I was having my 3YM30 running hotter when ever I tried to move up my speed to more than 6 knots.
After trying flushing out old coolant still did not change and used auto radiator flush and than flushed that after running my engine for a hour.
So after help from many here how to flush do this first to get any buildup in side the heat exchanger.
Nick
After trying flushing out old coolant still did not change and used auto radiator flush and than flushed that after running my engine for a hour.
So after help from many here how to flush do this first to get any buildup in side the heat exchanger.
Nick
While I was on my boat this morning I took photos of the various fittings you should find on your 3GM30F to drain coolant.
Photos help a lot more than just words.
Photos help a lot more than just words.
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Thank you all for your responses. After some searching, I decided to just drain, refill, run and repeat twice more to make sure I got all the old coolant out. With the exception of the of the drain by the lift pump (which was mounted vertically) they were all very easy to get to and made the job pretty easy. I was able to pull the hoses off the water heater and just let them drain down into rags. Took a while since I had had to let the engine cool between flushes.