Question concerning the single point drain system

Last Dollar

Last Dollar

Active Member
May 10, 2011
245
Huntington WV boating the Ohio River and lakes in
Boat Info
Sea Ray 225
Engines
5.0 Mercruiser
Will be winterizing for the first time on my 5.0 MPI 2003 model. It has the single point engine drain system. I'm wondering if possibly a passage or outlet connecting all these hoses together could ever block and prevent all of the system from draining. I can remember on my old Sea Ray V6 that after removing the brass plugs that I ran a small wire into each hole to be assured rust had not blocked the outlet. One year I can remember getting substantial amount of water out of one passage after pushing a small wire in the hole.
On a single point drain system I would have no idea if one section was blocked. Has anyone ever heard of a problem with this single point drain system??? It just seems like such a great idea but I feel like I'm cheating!! Man this is just too easy!!
 
Hey Dollar,

That is a great question, I to have the same system and have been wondering the same thing. I will be very interested in what answers you get. Thank you for posting.

Ed.
 
elevy said:
Hey Dollar,

That is a great question, I to have the same system and have been wondering the same thing. I will be very interested in what answers you get. Thank you for posting.

Ed.
Click to expand...

My engines also have the single-point drain feature. I think it's one of the best ideas Mercruiser ever came up with to easily winterize these engines. I doubt there would be any issues with clogging the hoses, but it is possible. In this setup, all of the hoses run to a manifold, so seawater is constantly flowing through all areas that these hoses are connected to. Whereas with drain plugs, nothing is flowing by, and there is a bit of a depression on the backside of the plug for debris to accumulate.

This will be my 3rd winterization of these engines and I haven't had any issues yet. Soon, I'll be opening this valve each time we come back from a trip, since temps are beginning to get close to the freezing mark at night. Once we're done using the boat for the season, I'll drain and then fill the blocks with anti-freeze through the thermostat housing.

Tom
 
I'm going to take a stab at this... the internal passages are not as small as the drain hole. If a blockage occured internally, I believe you would overheat during normal operation.

Collect the water and measure how much drains out... you should get about 5 gallons.
 
Very good point Tom, I never thought of it like this. Continuous water flow will keep the passages clear unlike a plug that sits at the dead end of the flow. I believe if this were a problem on the single point the forums would be lighting up like crazy.

Still I think it will take a few hours for the grin to fade from my face after I open the valve!!
This has to be illegal!!
 
Last Dollar said:
Still I think it will take a few hours for the grin to fade from my face after I open the valve!!
This has to be illegal!!
Click to expand...

I'm with you. For once, Mercruiser actually made it *easy* to maintain something on these engines!
 
Excellent, Thank you all for the feed back. Last year when I drained my blocks all my dock mates were jealous! I was done draining mine having a cold one and they were just climbing up out of their engine rooms, green with envy!!
 
Tom is right on the money regarding why the system shouldn't clog. But, I can also tell you that I have seen it clog. However, I believe what I've experienced to be more the "exception" than the norm. I was working on a boat this summer that had overheating issues (350MAG, single point drain). I ended up running acid through the engine... but in the process of preparing the engine for this I removed, among other things, the small hoses that go from the block to the drain manifold. The port-side hose was caked - nearly the whole length of it - with sand/muck. Once I removed the hose and started flushing the engine with water to see how much sand was still in the block, I found that there was actually very little in there. It all just gathered in the hose.

If someone would have winterized that engine, the way it was, the block likely would've cracked over the winter since all of the water would not have drained out and the person doing it would have been none the wiser.
 
"I was working on a boat this summer that had overheating issues" ......Good point.

It would be critical for owners to be aware of any overheating issues and relay this to their mechanic or dealer who will be winterizing the engine. Those folks should investigate to be sure all hoses are dumping properly into the single point collector. Now this brings up a very important issue. Does water circulate through these hoses during normal operation, are they part of the circulation path, or are these hoses just dead end streets that would certainly accumulate sand, silt and muck???? Wonder if clearing this one hose would have solved the overheating issue?

I think while running my engine up to temperature, I'm going to feel the hoses and see if they apparently have flow. They should feel warm after the thermostat opens shouldn't they?? That is, if they have flow. If not, they would be cold. It would be important to watch what comes out when you open the valve. If you see sand, silt and muck you may want to investigate.

For everyone to have confidence in this single point system we need answers to these questions!
 
Yes, the little hoses do have flow. But it is minimal. Meaning, the water doesn't "shoot" out of the hose - it comes out in a gentle arc. More than a dribble, though. And, yes, in a normally functioning system they would get warm.

In the case of this engine, this blocked hose was only a very small part of the problem. There was much more going on. Fixing just that hose would not have cleared it up.

It's important to note that if this was the only problem, then the engine would NOT exhibit overheating. The actual "clog"* on this engine was limited to the hose. There would still have been normal flow through that part of the block - as if it simply had the normal drain plug inserted directly into the block. In other words, we can't say that "a clog always equals overheating" - it's very possible to have a clog and not see overheating.

* I am quite sure there were other clogs (and narrowed passageways) in this particular engine, but none were apparent from draining the block. There's a lot more to what was going on with this block.
 
Last edited:
On my 2007 350 mag one of the hose fittings on the block was blocked. Merc put quick disconnect fittings on the block drain hoses for a reason I guess. I'm pretty happy I happened to do do a search on the single point system and on another forum there was a lot of discussion about it and to make sure and check the manifold check valves and block drains to make sure they are open.

If I didnt check those block drain hoses I could have had a bad spring. Of course if you are doing the through the drive running antifreeze thing it wouldnt matter..
 
Winterized yesterday and it took 4 gallon of the pink stuff poured down the block by removing the thermostat and filling the hoses going to the thermostat. I would say the block was dry when I started.

I ran it up to temperature before draining and felt the hoses going to the single point maniford device, they were luke warm. I'm not sure there would be a whole lot of flow in them during normal operation. I did notice some very slight discoloration and apparently rust particles when I first opened the valve but it was very slight and only lasted for a few seconds. Water poured into the bilge for quite a while. This is my first winterization on this boat and I don't want any surprises next spring. Hope Mercury Marine has engineered this thing well.
 
What drive do you have - Bravo or Alpha?
 
You're good to go.

Oh... you have the spin-on fuel/water separator, right?
 
Last Dollar said:
This is my first winterization on this boat and I don't want any surprises next spring.


You may want to also pour a gallon of anti-freeze in the bilge. I cannot get all the water out of my bilge and one year I believe the bilge pump was in the "pure" water froze and cracked.
Click to expand...
 
You must log in or register to reply here.

Forum statistics

Threads
113,117
Messages
1,426,408
Members
61,029
Latest member
Curious
Back
Top