FINMAN

i have a 496 mag closed cooling system engine in a 2003 Crownline. I am planning on draining the coolant and adding new. The manual says to remove the hex plugs that are located about 6" from the motor mounts on each side. I have found a large round plug on the port side of the engine just in front of the motor mount. It looks like it takes a large star torx type socket to remove it.
Is this correct, and if so, does anyone know what size that torx drive is?
I could not locate this same plug on the starboard side. The fuel filter is roughly in the location of where this plug might be.

thanks,
Fin

FINMAN

correction, the plug i saw may actually take an allen wrench instead of a torx. it was hard to see at the angle. if it is an allen wrench. Does anyone know what size it is? It looks pretty large.

thanks,

Cris

Raylar

The two plugs that you need to remove are two 17MM head hex plugs that are on each side of the block approximatly middle of right down low just above the pan/block rail joint . Do not try and remove the large hex brass plug on one side of the block about midway up the block where freeze plugs usually are on older BBc blocks as this is not ma drain plug and it takes a very big allen head socket to remove and should not be removed.
You should also run just a bit of fresh water down thru form the fill on the coolant bottle that will finish flushing any bigger particles of small buildup that may be in the system over the years. Make sure you put a little sealer back on the threads of the plugs when you re-install them.

Best Regards,
Ray @ Raylar

FINMAN

When looking at this picture. #14 on the port side looks to be inboard of the engine mounts.
http://www.mercruiserparts.com/Show_...FT+AND+PISTONS

i will pick up a 17mm allen and see what happens.
i would assume the starboard side would be in the same place. the fuel filter is in this area on the starboard side so maybe if i can remove the filter i will see the starboard plug.

thanks,
Fin

techman

Are there any other methods of changing/draing the coolant besides the block taps? Anyway to flush/fill using a hose attachment? Sort of like those prestone kits they sell for cars.

Raylar

Finman & Techman:

First those two plugs have hex heads like bolts and take a 18MM socket or an 8mm allen wrench in center.

No there is no other good way to drain all the coolant as most of the coolant is contained in the block and this is the only real way to get it out.

Best Regards,
Ray @ Raylar

Knot 4 Me

You could remove the hose on the circulating pump. I would think this would drain the fill tank, heat exchanger, intake, heads, and the upper portion of the block. You'd still have a good amount of coolant remaining in the block.

FINMAN

Thanks,
i have not seen a hex head bolt on the block that would drain the coolant. i did remove a plug that had a knock sensor on it thinking that would drain the coolant and noting came out when i removed it. I was located in the same location where drain plugs on my past boats with no closed cooling systems were but nothing came out so i am still looking for the plugs.

Fin

Raylar

These 18mm head plugs with 8mm allen centers are plugs not bolts and they are on each sides of the block in the middle area down by the junction of the oil pan flange and the bottom edge of the block. They are there just look harder.

If you are going to change the coolant then drain the blocks because the block holds about 70% of the coolant in both sides.

Best Regards,
Ray @ Raylar

FINMAN

Raylar,
thanks for the assistance with this. where would they be in reference to the engine mounts?

thanks,
Fin