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Old 06-07-2017, 02:36 PM   #1
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Default Coolant Change Mercruiser V8

I'm in the midst of rehabilitating a neglected 1995 SCR 2700 with a 7.4 litre V8 with 1100 hours. The "Mityvac 7201 Fluid Evacuator Plus" I purchased from Amazon.ca extracted warm oil via the dipstick in an hour with minimal effort. I need to change the coolant and wonder if anyone on this forum has done this with the boat in the water. Is there a way to extract coolant from a central location or is it time to call in a mechanic?
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Old 06-07-2017, 05:12 PM   #2
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So your engine is equipped with a closed cooling system option? No real good way to do this but pull the lowest hose on the closed loop which is the one from the HE to circulating pump. This will drain most of the coolant but not all. You could try to pull plugs from lower side of the block just above the oil pan to drain the rest.

Do you plan to flush and re-drain?
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Old 06-07-2017, 05:40 PM   #3
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Hello Mike, I'm wondering if I can disconnect the batteries to turn off the bilge pump, drain as much of the coolant as possible into the bilge and extract it with the vacuum gizmo I have available. I'm also wondering if there's some sort of add-on flush kit that attaches to a drain plug. I'm on the edge of hiring a marine mechanic to do this for me and advise me about other engine saving actions.
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Old 06-07-2017, 10:26 PM   #4
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I would try draining it into a container and not the bilge as it will leave a residue. I would then remove the t-stat and blow compressed air into the intake to push the rest of the coolant out.
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Old 06-07-2017, 11:32 PM   #5
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Drain it into the bilge and use a shop vac to get it out. Did this a lot of times to flush my engines after converting to closed cooling. No good way to catch the coolant nor to suck it out.
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Old 07-21-2017, 08:18 PM   #6
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Ok...I checked the coolant and found it's coffee coloured. I've scheduled a mechanic to come over and change it. I suspect he'll flush the system too. He wants to know whether it's red or green coloured. Can anyone answer this for me? (1995 SCR 2700 with a 7.4 litre V8) Also, where is the sea water strainer located? I can't seem to identify it among the many systems down there. (p.s. my prairie farm raised wife is beginning to calm down a bit during our initial 1/2 or 1 hour trips)
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Old 07-21-2017, 10:28 PM   #7
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Is the closed cooling system OEM or aftermarket? Either way I suspect it gave ethylene glycol coolant, green. If the raw water intake is through the drive pickup there is no strainer. Assuming you have a Bravo drive follow the input hose on the raw water pump to see it it goes to the transom assembly, if so no strainer.
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Old 07-21-2017, 11:40 PM   #8
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Have the mechanic do a complete inspection including a compression test.
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