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OMG!!! This drain plug issue...

Oxbow26

New member
So I attempted to drain my oil for changing since the guy that rebuilt the motor (4.3l) didn’t install the dipstick tube etc. after removing the drain plug I find that it is larger thread with a coarse pitch compared to the 1/2-20 of the banjo bolt assembly on the dipstick. So now I need to determine the right part numbers for a dipstick banjo bolt etc that uses this larger coarse thread. Does anyone have any clue what I’m dealing with here? I’m at my wits end with this one... 🤬
 
OK what exactly did this guy do? Rebuilt a 1986 4.3 V6, or intall a later engine? With the GM 4.3s there are many variations that are very complex over the many years of production. Start with the engine casting # which is on a pad behind the cyl head on the starboard side as its installed in the boat, then there is a serial # on the front of the block kind of right where the head bolts to the block. It will have a letter in it, T means it was built in Tonawanda NY and R means it was built in Romulus Michigan. These 2 bits of info will help you figure out what you have. Then there are other options. Volvo penta also used the long dipstick that goes to the bottom of the pan with the banjo bolt. I'm not sure of the thread differences though and what year they went to all metric. I would not be surprised to find some SAE and some metric on the same engine.
This is why, that when I need a new engine, I'm either going to buy a reman old style 4.3 like I have, so all my stuff fits, or a new GM marine vortec, I will make the modifications that are needed but only do it once. At least with those 2 options you know what you are starting with!
 
He rebuilt the original. Motor but then pan had rusted so he purchased a new pan that currently doesn’t match the thread size of the original dipstick banjo bolt. I have a machinist at work making me one with correct thread size as we speak out of stainless... ����
 
Ahh OK that makes sense. Lucky you have some one who can do that. I have sprayed the pan with Corrosion X or Boeshield at the start of each season and it has very minimal rust nothing even flaking. 100% salt water. If I had a new pan I'd scuff it with a scotch brite pad and brush on 2-3 coats of Rustolium black. I did this on my exhaust manifolds and they look new. 100% salt water use moored on a salt water mooring 6 months of the year. The paint those pans come with is too thin same with manifolds, brush on gives a much thicker coating.
 
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