MerCruiser single point drain leak.

[Prop head]

Greetings all.
I am having a small leak into my bilge from the drain on my MerCruiser single point drain system. The water is leaking out the drain port of the bottom after the valve has been closed. The engine was removed in the fall and fully drained prior to removal. This is the first year the drain has leaked. Im guessing old dry seals. The boat is about 20 years old. I have been looking for any videos or information in reference the internal workings to possibly fixing the drain instead of buying a new drain valve (Yes I'm Cheep). I have not seen much for diagrams or parts. Has anyone taken the valve apart or fixed this problem. Thanks for the help!!

 

[Grub54891]

Remove the entire single point drain system. The are prone to clog up and wreck your motor over Winter from freezing. Install regular drain plugs in proper locations.

 

[flashback]

I agree, those are an accident waiting to happen..

 

[Longislandjoe]

It's true the single point drain system is maybe one of the worst ideas Mercury has ever had, but removing it is not as easy as the many who would advise you to "just take it out" would have you think.

I noticed a leak coming from the single point valve on my 5.0 MPI last fall when i was winterizing, and looked into what it would take to just replace the whole system. Yes, a marine mechanic could probably do it in an afternoon, but in reality it involves fabricating connectors, and it's really a lot more complex than "just take it out." It's lot easier for the weekend warrior like me to just replace the single point drain valve.

That said, these guys are right, when winterizing you cannot rely solely on the single point drain system, you have to disconnect the quick connectors from the block and poke around in there, making sure the block drains completely. Those little ports can easily become clogged with rust and marine debris, so make sure your block drains completely when winterizing. I've been doing it this way for years and no problem.

 

[Grub54891]

If you are discounting those fittings at the block and other places to poke them out, you are just adding more work to hook it back together. You’re down there, just spend the extra time to remove it. From then on it’s just like it should be.

 

[Longislandjoe]

Again, it's easy to say stuff on the internet. But the way the single-point system is run is quite complicated, and it's not a small job to remove it. I suggest you look into it a little more closely, as I have. I think you'll be less inclined to give this kind of off the cuff advice.

 

[Bondo]

Again, it's easy to say stuff on the internet. But the way the single-point system is run is quite complicated, and it's not a small job to remove it. I suggest you look into it a little more closely, as I have. I think you'll be less inclined to give this kind of off the cuff advice.

Ayuh,...... Somewhere here at iboats, Bt Doctur did a posting of how he sweat together some hardware store fittings to eliminate that Merc guaranteed frozen busted block system,....

 

[QBhoy]

Hi. I found that my drain valve had a very soft sealing point. As in, if you turn her down too tight, it will leak. If you back off a little, a bit of downward pressure and only just softly seat the valve, it will hold. On mine at least.
Still never trust mine when it comes to winterising though. I always pull each of the individual fittings around each source, to make sure.

 

[Lou C]

These things seem to work OK when the engine is new but as it ages, cast iron naturally sloughs off rust flakes, that wind up clogging drain ports. That is the problem with these systems.
On my boat I reconfigured the rear of the boat to make the engine more accessible so that I could have better access to the block drains. They are the worst of it, the manifold drains, raw water intake hose, and big hose that connects the front water pump and thermostat housing are easy to get at. If there were just an extension of the block drains, that alone would make it easier to get at as long as you could rod them out.

 

[QBhoy]

These things seem to work OK when the engine is new but as it ages, cast iron naturally sloughs off rust flakes, that wind up clogging drain ports. That is the problem with these systems.
On my boat I reconfigured the rear of the boat to make the engine more accessible so that I could have better access to the block drains. They are the worst of it, the manifold drains, raw water intake hose, and big hose that connects the front water pump and thermostat housing are easy to get at. If there were just an extension of the block drains, that alone would make it easier to get at as long as you could rod them out.

Touch wood, I’ve managed to avoid the metal flakes, by leaving her filled with antifreeze each winter. Still check the fittings each year just in case though. She’s now 20 years old.

 

[Lou C]

I mix my own! Cheaper & better than what you can buy....

 

[Grub54891]

Again, it's easy to say stuff on the internet. But the way the single-point system is run is quite complicated, and it's not a small job to remove it. I suggest you look into it a little more closely, as I have. I think you'll be less inclined to give this kind of off the cuff advice.

Welp. Being a marine mechanic, I’ve done it. Internet didn’t come in to play there. I just got rid of what didn’t need to be there.

 

[QBhoy]

I mix my own! Cheaper & better than what you can buy....View attachment 377903

Me too.

 

[Scott Danforth]

Again, it's easy to say stuff on the internet. But the way the single-point system is run is quite complicated, and it's not a small job to remove it. I suggest you look into it a little more closely, as I have. I think you'll be less inclined to give this kind of off the cuff advice.

having worked side by side with many of the mercury marine engineers, I can tell you the system is over complicated and prone to failure. I can also attest that when it does fail, it will take out your block.

its actually quite easy to remove once you understand the cooling system

The only reason the 3-point and single-point system exist is for marketing reasons not because its better.

 

[Lou C]

Instead of that Rube Goldberg-ish maze of hoses & plastic they SHOULD have just made at least a half closed cooling system STANDARD!
If you want to get a headache take a look at the parts breakdown on a modern Merc 4.5 just for the raw water cooling system. Somehow my old OMC Cobra made do with ah 5 hoses!
What I’m going to do in the fall when I install my remote oil filter is to extend the block drains with 1 hose on each side so all I have to do to drain it is remove the side panels behind the rear seats. The extended block drains will be set up so they can be rodded out. Manifold drains & big hose from the stat housing to the circ pump are easy to get at.

My brother has a 2020 Chapparal with the 4.5. So far it’s drained fine but I told him eventually he’s going to have to deal with this. Oil change & single Pt. drain are easy on that engine but due to poor access it will be tough once it starts clogging up.
Next idea:
Take boat to best fiberglass shop on Long Island & pay them to make the side panels removable with something like Dzuzs fasteners. Then the whole stupid thing can go in the trash!

 

[Bt Doctur]

 

[Lou C]

sure beats this abomination:

Raw Water Cooling, Cooling Hoses

Raw Water Cooling, Cooling Hoses

www.mercruiserparts.com

plus:

Raw Water Cooling, Crossover Assembly

Raw Water Cooling, Crossover Assembly

www.mercruiserparts.com

and:

Water Distribution Housing, Rod Actuated

Water Distribution Housing, Rod Actuated

www.mercruiserparts.com

add up all of this, you could have paid for a good portion of a heat exchanger, have an engine that runs at the temp it should (160-180 instead of 140) and easy to winterize as well.

 

[Bondo]

Thank you, BD,......