mk 55H

[speeder]

Q.
replacing lower racing unit back on to exhaust leg
esp.* the water tube from motor down to where tube fits into the top of lower unit

what size copper tube should be used ?

Q. when tube fits into lower unit,
at the top of unit,
are there any seals that
seal around copper tube
thank you
ralph

[ZUL8TR]

55h cooling

Q.
replacing lower racing unit back on to exhaust leg
esp.* the water tube from motor down to where tube fits into the top of lower unit

what size copper tube should be used ?

Q. when tube fits into lower unit,
at the top of unit,
are there any seals that
seal around copper tube
thank you
ralph

I don't have a 55h but my 20h lower unit has a rubber O ring seal that fits into a bored recess in the top of the gear foot that the copper cooling tube fits into.

I do not know the size of the 55h copper tube but it might be the same as the 20h which is 3/8 OD.

[trident]

55H gearcase

Whoa! That's not an O-ring as original equipment. Its a rubber straight walled sleeve PLUS a metal bushing. The two part stack projects slightly above the case top, so that when its tightened down, the rubber compresses some and expands outward in the counterbore to seal.

Now the trick, if you don't have those parts. You could just stack several 'fat' O-rings in there, to get that effect, or in a pinch, just silicone seal it.

[ZUL8TR]

Whoa! That's not an O-ring as original equipment. Its a rubber straight walled sleeve PLUS a metal bushing. The two part stack projects slightly above the case top, so that when its tightened down, the rubber compresses some and expands outward in the counterbore to seal.

Now the trick, if you don't have those parts. You could just stack several 'fat' O-rings in there, to get that effect, or in a pinch, just silicone seal it.

Right on the O ring wrong call, it is as you say a straight wall rubber sleeve.

[G Stillwill]

A rubber o ring goes under the flare at the top of the tower also, you have to put it on before sliding the tube down in the tower.

[John Schubert]

rubber grommet

A rubber o ring goes under the flare at the top of the tower also, you have to put it on before sliding the tube down in the tower.

George,

On the 2 cylinder only. On the 4 cylinder there is a grommet with an internal flange that fits in to the bottom cowl from the underside. The tube nests in to this grommet. The flange as well as the cowl makes a stop so the water tube stays in place & does not extend through the bottom cowl. Just finished my 55H.

[jimm007]

MK58 block with quickie lower

I have run into an insufficient cooling issue with my recently built engine. Block flows well. Lower unit pumps well. Suspect issue is the seal 26-25192 at top of water tube or maybe the C-12-20684 at bottom of tube. While fairly tight, the modified tube can move up/down about 1/8" so water may be dropping down into tower or blowing by at lower seal. May have to put some type of seal under the 25192 to prevent tube from dropping down. Looking for 25-24961 to see what it does (and where it goes). Also, drilling a 3/8" hole, to supplement the three existing 1/8" holes at bottom of #4 cylinder in water jacket has been suggested along with 1/8" pipe tap fitting at top of block to let cooling water dump overboard. The stock block now has two 15/16" dump holes at bottom of exhaust manifold cover plus the 1/8" pee hole.