water heater engine side connections - warning

[mdidomenico]

so in my quest to cleanup the engine, i pulled out the hose fitting on the engine side underneath the thermostat, which is this part number 301519 from universal.  or part 6 on this diagram

http://www.marinedieseldirect.com/catalogs/catalog_group.php?owner=mdd&catalog=200142&model=M-25%20/%20M-25XP%20/%20M-25XPA&page_ident=200142-33&manufacturer=Universal&title=Water%20Flange%20Group%20and%20Temp%20Sender&size=600

believing it's a threaded fitting, it was reasonable to assume i should just be able to unscrew it.  clean it up.  then screw it back in.  oh no, no no, life couldn't be that simple.  it appears this fitting (at least on my '89 vintage) engine is pressed in.  no threads or if there were some how they separated from the fitting.

now what to do.

the hole (engine side) measures to ~10-11mm and the fitting is ~10mm.  that's roughly .39", so it *might* be tap'able back to 1/8" npt.  a 1/8" npt tap is .33".  i think the hole might be a millimetre to big though.

i'd have to jump to the next size, which is 1/4" NPT or .43".  i put a 7/16" drill bit up against the hole, it looks like there's enough room, but just barely.

i thought about just wire wheeling the fitting and jamming it back in with a dab of jbweld, but i'm not sure how much i'd trust that.

if none of those work, it's a $281 mistake.  and if i have to remove the lower thermostat housing i'm not sure if the bolts will clear the back of the water pump housing.  which would necessitate removing the head to get the lower thermostat housing off.  which surely makes it a catastrophe.

[KWKloeber]

Maryland

You're lucky -- better to find it out now than be stranded somewhere.
The lower Tstat housing ("water flange") is 1/8" JIS thread (as I explained is functionally equivalent to 1/8" BSPT thread.)  And so is the water pump.  If you zoom in on mine you can see the bronze elbows I used to direct my hoses where I needed them.





If you attempt to tap the hole to NPT or even JIS, I DOUBT you would line up with the old thread (even if it exists anymore.)  If you can tap it to 1/4" NPT then you could use a normal 1/4" npt x 3/8 hose barb.

I see no reason to remove the head.  At worst if you can't R&R the water flange with the pump in place you'd R&R the gear case (mistakenly called a timing cover.)  It's not sailing but also not the end of the world.  The water flange bolts are short but the hang up might be getting it off the stud on the other end.

If you need a new water flange you might get it from Kubota *if they are still available**.  Probably 80-90 boat bucks.  They are usually about $50 salvage -- I might have a spare one.

[mdidomenico]

If you attempt to tap the hole to NPT or even JIS, I DOUBT you would line up with the old thread (even if it exists anymore.)  If you can tap it to 1/4" NPT then you could use a normal 1/4" npt x 3/8 hose barb.

i doubt it too, but it's worth a shot before i remove more meat from the housing.  i had to order the 1/8" npt tap, so i'll check it this weekend or drill it out to 1/4"

I see no reason to remove the head.  At worst if you can't R&R the water flange with the pump in place you'd R&R the gear case (mistakenly called a timing cover.)  It's not sailing but also not the end of the world.  The water flange bolts are short but the hang up might be getting it off the stud on the other end.
spare one.

the only reason was because i wasn't sure how long the bolts are and the space between everything down there seemed fairly tight.  it looks like from the diagram they *should* be 14mm long, which might just clear everything.  either case i really don't want to go down that road.  i'm all for sprucing up the engine a little, i wasn't looking for surgery

picking up a salvage one sounds like a good idea, even as much as just to practice on.  i'll poke around the local area and see if i can find one

[mdidomenico]

The 1/8" size R drill bit was too small for the hole, so up to 1/4" i went.  Tapping went easy enough.