View Full Version : Block Draining ?

10-04-2004, 09:09 AM
I Started to winterize my 94 PS 190 this weekend, Everything was going as expected until I opened the petcock to drain the block. No water came out. Exhaust manifolds were full and the boat ran fine all summer - no problem over heating. I removed the petcock from the boat thinking it was clogged, but still nothing. Any suggestions? should I worry about water left in there? Should I worry about no water in there? Any help is greatly appreciated.


10-04-2004, 10:05 AM
Try sticking a coat hanger in the holes and see if there is any sediment or scale blocking up the holes. You should indeed worry if water didn't come out.

Make sure that all of the hoses are disconected and the impellor/raw water pump cover is removed. Water must come out...are you saying that no water at all came out ?? Not from any of the hoses or block petcocks or from the exhaust manfolds ?

The side of the block is the low point in the cooling system...if water didn't come out, it is still inside. If the temperature gets below freezing you will crack your block.

10-04-2004, 10:31 AM
94PS- by "Should I worry about no water in there?" do you mean that the cavity was dry? If you stick a wire into the petcock hole and it doesn't loosen a clog so water can get out, then yes, you should worry about it. Water absolutely needs to get in and out of this area. If it's not getting or out, whatever is keeping it from doing this needs to be fixed.

If you have an air compressor with a shut-off valve in the air line, screw a fitting like the ones in your air tools into the petcock hole. 1/4" fittings should be the same size. With the hoses off of the water pump etc, lower the pressure and open the valve on the air line and see if the pathway is clear. You'll hear the air getting out of various places in the cooling system if it's clear. If it immediately sounds like the air has stopped, you have a clog. If it was dry and the petcock has a slight leak, that could explain the cavity being dry, provided the motor hadn't been run for a long enough time.

10-04-2004, 10:40 AM
This is why I always use to drian the block and manifolds as much as possible, then suck antifreeze thorugh the system with a fake-a-lake.
If any water is trapped, the antifreeze with take care of it.

10-04-2004, 11:27 AM
Exhaust manifolds were full. I didn't unhook the hoses as I was planning on using the fresh water hose to add anti freeze. I was just surprised no water came out. It is possible that the petcock leaks. Am I correct that there is only one drain on the block. I will try to clean out the petcock hole to see if I can get any water out of there. My last boat had a drain on both sides of the block. On the other side where I was expecting to find a drain plug, the is a sending unit . I am assuming it is for the tempo gauge. Should I pull this also? Thanks again for the help.


10-04-2004, 11:44 AM
The sender on the other side is the knock sensor and it holds water in the block just like the petcock. You need to remove that, too. V6 and V8 blocks have 2 cavities and 2 plugs. Use a 7/8" wrench to remove it. When you reinstall it, go hand tight + 3/4 turn. You don't need to overtighten it since it's tapered thread.

lakes Rick
10-04-2004, 11:46 AM

The sensor in the block drain is a Knock sensor for the computer/distributor... Pull off the electrical connection on top and there is a "nut" on the top of the sensor.. Put a deep socket on it and remove it.. It should not be very tight, and when you reinstall it hand tighten only, or just a snug up with a wrench.. I pull mine out every year to drain the block...

If you havent done the coat hanger trick yet, you need to do this first before you do anything else......

10-04-2004, 01:06 PM
Bump start it with all the petcocks & drains open. This will also blow the water out of the mufflers which can crack if the water in there freezes. Don't run it for more than a few seconds though.

10-04-2004, 03:16 PM
Something I did the first couple of times I drained my block was to pull the petcocks and let everything drain. Then I poured some antifreeze in a hose until I saw it start to drain through the petcock. JimN’s comment on the compressed would be a good method if you have access to an air compressor. I agree though that if nothing comes out, something is wrong.

10-04-2004, 05:41 PM
It must be block for sure!

10-13-2004, 05:04 PM
I have a '93 Prostar 190 with the 351 Ford. I can see the obvious petcock on the port side at the bottom of the block near the back.

On the starboard side there isn't an obvious petcock. Also, I don't believe the carb'd motor's have knock sensors? The hose for the hot water side of the shower is attached to a fitting in the block, near the front on the starboard side. Is this the drain for that side?


10-13-2004, 07:51 PM
Brian- that is the drain hole for that side, but make sure to lower the bow when you drain it so more water comes out. I never liked the hole being so high there, but the motors do come from the auto industry and they don't mount the motor on as much of an angle.

10-14-2004, 07:59 AM
Brian- that is the drain hole for that side, but make sure to lower the bow when you drain it so more water comes out. I never liked the hole being so high there, but the motors do come from the auto industry and they don't mount the motor on as much of an angle.

Thanks JimN, I was also concerned that it seemed high, that is why I wasn't sure it was the drain.

10-14-2004, 08:21 AM
chaps.....i'm using the boat this weekend,but they have forecast 32f for sat night.....i don't want to winterize it as i am going to use it most weekends thru' the winter...will undoing the hoses and draining it be enough???? Dec and Jan i will take it home where i have a heated garage,so i am not too bothered then..but at the mom.it is on the boat lift.....any views????

p.s. have never had an inboard b4,,,so which hoses do i loosen??doh!!
p.p.s i have an electric greenhouse heater i was going to leave under the box...it cuts in at 37f ,,any thoughts?