Merc 4.3 cant find 5th drain plug?

EricT22

Seaman Apprentice
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Jul 5, 2018
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43
As the title states i cant find the 5th drain plug. I drained each of the manifolds and each side of the block but everything i read says there should be 5. Engine serial number is 0B930934 if it helps
 

zellerj

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Dec 13, 2017
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135
Make sure the engine is tilted back so the manifolds drain (raise front of trailer if you have one, otherwise pour antifreeze down the hoses that go into the manifold. Pull off the hose to the engine water pump and drain that. Pour some pink antifreeze into the hose going to the engine water pump until it comes out the thermostat housing (where the hose was connected). Pour some antifreeze into the hose coming from the stern drive until it runs pink out the stern drive (this gets the power steering cooler too). and you should be good to go. My 1989 4.3 only has four drain plugs.

Some power steering coolers have a drain plug, perhaps that is your fifth. The PS cooler is by the engine mount on the port side of the engine. It is just a thick part of the hose system that comes up from the stern drive.
 

Fun Times

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As the title states i cant find the 5th drain plug. I drained each of the manifolds and each side of the block but everything i read says there should be 5. Engine serial number is 0B930934 if it helps
Not all engine models have 5 plugs....Some of the older engines didn't have plugs in certain areas like they have now.

The serial number you posted is for your stern drive not the engine (which having the correct # helps a lot) but knowing that serial number (0B930934) helps some by telling us that you ought to have an 1988 year boat and engine?? if still factory stock? Correct?

Since your 4.3 doesn't have any other drain plugs means you will need to pull some water hoses off in order to properly drain the cooling system. Such as the water hose Between the water circulating pump and thermostat housing, the hoses down at the power steering cooler, The inlet water hose between the engine and transom housing/stern drive....And anywhere else it may look like water can collect/hold.

STANDARD COOLING SYSTEM , NEW DESIGN Item number 23
STANDARD COOLING SYSTEM , OLD DESIGN Item number 21.
CYLINDER BLOCK AND CAMSHAFT item number 2


0B930934 = MERCRUISER R.H. ROTATION ALPHA 1.84:1

Being a possible 1988 model year 4.3, these should be your parts but again just guessing without knowing the serial number of the engine....https://www.mercruiserparts.com/4-3l-2-bbl-gm-262-v-6-1988-1992-0b7
 

EricT22

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Jul 5, 2018
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43
Thanks for the reply. Thats pretty much what i have done so i hope I’m good. Boat is an 88 so makes sense if thats how yours is. No plug on the ps cooler so i pulled hoses and did it that way
 

EricT22

Seaman Apprentice
Joined
Jul 5, 2018
Messages
43
Fun Times. Thanks for that answer very helpful!!!! That’s the number is located on the engine so i assumed thats what it was but my outdrive has no serial numbers on it as they are worn off so I’m glad you pointed that out. Thanks for the info
 

Maclin

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May 27, 2007
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6,761
I believe some 4.3's have a plug on the front of the intake manifold that is a drain point.
 

harringtondav

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May 26, 2018
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I believe some 4.3's have a plug on the front of the intake manifold that is a drain point.

My 4.3 has that plug. The manual states it's a hot water supply for a cabin heater. It's also a good location to fill the block with antifreeze.
 

QBhoy

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Mar 10, 2016
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8,286
Look down low on front of engine. Some have a plug facing down the way on an elbow.
 
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