Check your Antifreeze mix after winterizing!

So, this is interesting.

Typically on my SN I drain the block/manifolds/heater, then take a bucket of Sierra AF (it's PG based but automotive grade- really good, expensive stuff), start up the boat to suck up 3 or so gallons and I'm good to go. I always like to take a little sample of the AF from the block afterward and throw it into the freezer just to make sure that there was no mysterious residual water which would cause a dilution of the mix.

So, I was deep in the northwoods, winterizing my 2nd "other" ski boat. This boat has the little petcocks on the motor and manifolds for draining, which is really handy. However, a couple of them were a little slow to drain. As such, I was sure to remove them and probe around with a small screwdriver to ensure that the water had drained fully. I was planning on just leaving the block dry (this boat doesn't get the full treatment I give the "primary boat" for a variety of reasons but mainly because I'm 300 miles from my garage) but decided to backfill manually with a little RV AF that I had left over from winterizing the cabin. So, pour about 1 gallon in through the t-stat housing input hose. Why not, right?

I bled off a sample from the block petcock and threw it into the freezer. The pic below is the result! Needless to say I drained all of the AF and left the block dry. The freezer is "extreme" cold, to be sure, but still!

The lesson here is never assume your AF mix in the block is good to go. I've done this for 10 years of inboard ownership and this is the first time a sample failed the test! I don't care how/why it happened, but it did. I was 100% positive the block was dry pre-AF.

kytom2 wrote: Was it a 50/50 mix or straight Anti-Freeze, does it really make a difference?

It definitely makes a difference... its either meant to be diluted ~50/50 or not at all, in order to provide the freeze protection as-advertised. I believe the propylene glycol that Joel used is meant to be used full strength. My guess is that the block had a bit of residual water in it prior to backfilling!

I popped a freeze plug on a PCM 351 many years ago, or I assumed I did as it was gone in the spring. Never found it though. Since then, I pour a half gallon of minus 50 into the block after I have drained the water out and have put the plugs back in. I pull the plugs and let the anti freeze drain out to purge any water that may have been left in the block. I then fill with 3 gal of minus 50. Supposedly the minus 50 stuff delutes quite a bit with just a little water. If you're not going to fill it right up with 3 gal of the minus 50, your better off to drain it all out and leave the plugs out.

63 Skier wrote: That sounds like a good thorough method Bruce. Sorry if this is a minor threadjack, but ..... I winterized my '98 for the 1st time yesterday. I ran the engine up to temp on the hose, shut down, removed hose, and drained the block and the raw water strainer. I then re-started and sucked up 4 gallons of RV pink antifreeze. I assume this takes care of the tranny cooler, all hoses, manifolds, and of course most ends up in the block. Sound OK to you experienced 351 guys? My only concern was thermostat operation, I assume that it doesn't impede the AF from getting anywhere.

That's a fine method. As exhaustively discussed in other threads, the T-stat has nothing to do with water entering the engine as the T-stat housing has a permanently open bypass hole to allow fluid into the motor.

Do empty the strainer if there is any AF in there, it's not good for the nylon housing.

M3Fan wrote: As exhaustively discussed in other threads, the T-stat has nothing to do with water entering the engine as the T-stat housing has a permanently open bypass hole to allow fluid into the motor.

Joel,
You are forgetting the at the bottom of the circ pump, it has open ports to the block! You do not need to worry about the T stat at all.