[Public-List] ...a small victory

[Gordon Laco]

Hello Gang - 

I’ve had an issue developing for several years in Surprise’s late model Atomic IV.   Each fall when I’m winterizing the engine, I remove the brass drain screws from the engine block and exhaust manifold.  The manifold screw goes in and out easily, but the one I remove from the block has been getting tougher and tougher to replace.

From the mashed threads on the slug, I have guessed that the threads in the iron engine block have become corroded.  These last few years it has be extremely difficult to get the brass slug to thread in at all…I’ve had to hope for the best with the thing barely in… and once while motoring last year we had the tenuously threaded slug blow out.   I was amazed at how much water the engine pumped into the boat through that small aperture.

So when winterizing the boat a few weeks ago, I noticed with great dismay that the brass slug on this particular drain basically fell out in my hand, threads worse than ever.  I wondered how I was going to get it back in when spring came…

I’d thought about trying to run a thread cutter in to clean up the threads, but the starter motor is too close to the block and there isn’t room to align the cutter straight for it’s run in.   I thought about getting a bronze bristle gun bore cleaner and turning that in and out a few times to see if that would help by grinding away corrosion in the threads, but the nearest gun store where I could buy one is a couple hours drive away, and besides, it might not be enough to repair the female threads in the drain hole.

So laying here on my couch in front of the fire, it occurred to me that I might be able to get a thread cutter…and cut it down to a length that would clear the starter motor… then grind new flats on the round shank to take a wrench.   I thought about this a lot when not working on other things.  I mentioned the issue to a friend who used to teach marine engine mechanics where I taught rigging… he listened then said ’So why don’t you just pull the starter motor off to get it out of the way?’  Ha, easy for you to say Rick… thought I.  One thing he did tell me that I hoisted aboard was that there are tiny valves available that have the same brass screw-in part as the blank slugs that are normal for the engine… once I got one of those in, I’d never have to worry about the threads again when draining the engine.

So I went to our local auto supply places and showed them one of my old slugs with mashed threads… and asked for some new blanks, and also for some of the ones with valves… and a male thread cutter to suit the pipe thread for same fittings.  I bought several of each type of slug so as to have some to drop or otherwise mangle and the cutter. The whole pile cost me about $18 with tax.  So far so good.

I measured the clearance between the drain hole and the starter motor so I’d know how much to cut off the thread cutter and found I’d have to lose about 1/3 of its length.   Into the vice went the thread cutter (with soft aluminium protecting it) and I started sawing.    No surprise to everyone else I’m sure, the hacksaw made no impression on the very hard steel of the cutter.   Hmmm.

Aha - a cutting on my grinder.  I dug my grinder out and in about a minute had the shaft cut.   Then I used my bench grinder to put four flats on the round shaft, ending up with a nice fit to my 3/8” wrench.

Away to the boat… it’s not cold so I figured it was a good day to give the repair a try.   I greased the thread cutter… lined it up with the hole, and with my index finger on the end pushing, began slowly turning the cutter with the wrench.   Man, I was glad I took the trouble to make the cut end of the thread cutter smooth!  At first I couldn’t get the thread cutter to catch, but then I felt it firm up… and I was able to remove my pushing finger.  I turned it a long way in, than back out.   

Now for the valve/slug.   It caught the fresh threads easily, but i discovered that the butterfly wing on the valve makes contact with part of the casting of the engine.  Hmmm, I could grind those off a bit, I thought.   In the mean time I tried a regular blank slug and in she went, nice and easy complete with grease to inhibit future corrosion.

Success!  The Dutch say that worries are like stones you carry in your back pack… well now I’ve got one less pebble in there…

Can’t wait for spring.

Gord
#426 Surprise