Plastic Block Drain Plugs

[Scott Danforth]

wingless, if you want to use plastic below the water line, have at it. if you want to use plastic in your boat, have at it.

I have spent decades replacing broken plastic bits on personal vehicles/boats/equipment as well as dealing with warranty for failed plastic parts.

there isnt a naval architect or anyone that actually services boats that I know that would use anything but naval bronze or stainless for a thru-hull

the marlon just barely meets the 500# testing requirement when the fitting is new.

I sure would hate to have a 1" diameter column of water spewing 2000 gph

ABYC and CFR 33 also requires a yearly inspection which 99% of most non-classed boats do not get.

 

[wingless]

the plastic drain plugs are recommended to be replaced every year.

Please provide the link showing that recommendation.

FWIW, on my boat if these parts were to fail while stationary / docked, that failure would not cause water intrusion.

If these were to fail while underway, then I would get alerts at the helm and my three bilge pumps would have zero issue remaining ahead of the raw water pumped water ingress.

wingless, if you want to use plastic below the water line, have at it. if you want to use plastic in your boat, have at it.

As was stated, a failure of these plastic parts would cause zero issue on my boat.

ABYC and CFR 33 also requires a yearly inspection which 99% of most non-classed boats do not get.

The CFR 33 was searched and no reference was located for that requirement. Where is that annual inspection requirement defined?

Which ABYC standard / section defines that annual inspection requirement?

 

[H20Rat]

if you use proper maintenance practices...
OMC and Volvo used brass plugs...that do not corrode...last forever...and all you have to do...is put a bit of Evinrude gasket sealer/Merc Perfect seal on the threads...and they will not leak...nor will they get seized in the engine...even on raw water cooled blocks and exhaust manifolds...so WHY go to a plastic plug that can break...off in the engine...in an nearly inaccessible place...

So you are advocating a fair bit of maintenance on the metal plugs, but yet didn't mention that you can replace the plastic plugs every couple of years and not deal with that. Consider as replacement part of normal maintenance, or more like preventative maintenance.

Personally, I don't have evinrude gasket sealer on my boat, so doing your routine sounds like a PITA. Every couple of years, I throw away my blue plastic plugs, and put a fresh set in. Costs $3. Zero chance of damaging threads with cross threading, far easier to get out without a wrench, and I have never had one that I swapped break off on me. I HAVE had to deal with metal plugs that were either seized or cross threaded though. (I did have to deal with one broken blue plug from a previous owner that never swapped. couple seconds with an ez-out and I was good to go.)

 

[Scott Danforth]

wingless you are correct, it is not in there as I thought it was.

after a few discussions with a few people

classed boats require periodic inspection and a rebuild every 5 years at a minimum (sooner if the underwriter requires)
Most classed boats will use cupro-nickel, silicone bronze or stainless. this is primarily for fire protection.
Classed GRP boats are few and far between, however those that are, the requirements for the engine room is that it is a firebox to prevent the remainder of the hull from burning to the water line

regarding the Marlon thru-hulls, they have a 5 year life expectancy. they are primarily used on "toy boats" or recreational boats such as most of the people on iBoats. they do seize up if not used often and lubricated often.
they also are not fire resistant.

also, on non-classed vessels, the default is to follow the recommendation of the manufacturer, however from a legal/recommendation standpoint, its basically a free-for-all.

back to the topic at hand. I still would never use plastic in an engine bay.

also, perfect seal is an expensive label on Permatex #3 (Aviation sealer)

 

[wingless]

regarding the Marlon thru-hulls, they have a 5 year life expectancy.

The only link I discovered showing a five year seacock lifetime was this one regarding dezincification resistant DZR CZ132 CW602 brass.

Nothing was located showing a five year lifetime on Marelon parts.

Please provide a link showing this information.

 

[Lou C]

So you are advocating a fair bit of maintenance on the metal plugs, but yet didn't mention that you can replace the plastic plugs every couple of years and not deal with that. Consider as replacement part of normal maintenance, or more like preventative maintenance.

Personally, I don't have evinrude gasket sealer on my boat, so doing your routine sounds like a PITA. Every couple of years, I throw away my blue plastic plugs, and put a fresh set in. Costs $3. Zero chance of damaging threads with cross threading, far easier to get out without a wrench, and I have never had one that I swapped break off on me. I HAVE had to deal with metal plugs that were either seized or cross threaded though. (I did have to deal with one broken blue plug from a previous owner that never swapped. couple seconds with an ez-out and I was good to go.)

do you winterize? If so all you do is remove them to winterize...when the engine and manifolds drain...put gasket sealer on them (Permatex Aviation works just fine as well as the OMC or Merc stuff) and reinstall. "far easier to get out without a wrench" until one breaks off....then...a metal plug that can't break...will seem like a better idea...which is why Hardin Marine is selling them!

What's the cost of replacing these things every few years? My old OMC has the same plugs in it...ah well...for 31 years...

Oh and on any cast iron engine I haver ever looked at...besides Merc I/Os...the engine block drain plugs....are NOT plastic...face it...its not one of Merc's better ideas...in the category of foolish things like:
Plastic water pump pulleys (failed)
Plastic water distribution housing for one point drain (clogs due to cast iron rust flakes, then cracks the engine block because it does not drain...housing itself can crack)…

That, and the rat's nest of cooling hoses on the new 4.5 V6s would turn me off to a Merc I/O in the future.

 

[muc]

Wow, plastic seems to get people to voice their opinion. Here’s mine.
I like the blue plastic drain plugs. No tools needed and they don’t seem to burn your fingers. They rarely break if they aren’t cross threaded or over tightened. Most of the problems with them seems to be people losing the o-ring. If they do break, they are one of the easiest things to repair.
Matter of fact, I kind of like a lot of the plastic on newer engines. The plastic cover over the flame arrestor is so much better then the old aluminum one. How about the gear lube bottle, kind of nice to see the lube level. Couldn’t do that with a metal bottle. And the plastic inserts in the newer oil pan gaskets? Seems to help keep amateur mechanics from creating oil leaks. I’ve had less trouble with plastic floats in carbs than I did with the brass floats.
I will agree that manufacturers can sometimes use the wrong grade of plastic. The gear lube hose connector in the gimbal housing is pretty bad.

 

[muc]

Oh and on any cast iron engine I haver ever looked at...besides Merc I/Os...the engine block drain plugs....are NOT plastic...face it...its not one of Merc's better ideas...in the category of foolish things like:
Plastic water pump pulleys (failed)
Plastic water distribution housing for one point drain (clogs due to cast iron rust flakes, then cracks the engine block because it does not drain...housing itself can crack)…

That, and the rat's nest of cooling hoses on the new 4.5 V6s would turn me off to a Merc I/O in the future.

Volve used plastic drain plugs on their newer raw water cooled engines before they went with freshwater cooling standard.

Haven’t seen any failed plastic water pump pulleys, but I haven’t seen a plastic water pump pulley. Who used that? Maybe your thinking about the power steering pulley? Yes that was bad.


Have you seen an engine freeze damaged because of the single point drain system? I’m asking because I was a marine mechanic for over 30 years and never saw or heard of one that had been properly winterized. I think this is one of those “old wife” tales that get started on the internet. The system is working real good as it was designed to here in Minnesota. I don’t know how well it works in saltwater, but this system wasn’t designed for saltwater. That’s what freshwater cooling is for. It works great to extend the boating season. It was never designed for winterizing. MerCruiser is pretty up front about that.

All the hoses are needed to keep the catalyst at the proper temperature. MerCruiser uses a poppet bypass system to do this, Volvo uses thermostats on the exhaust manifolds. Time will tell which system works best, right now both have some issues. But the only other option is an outboard. The trouble with them is cost. An extended warranty on a 400hp outboard is $14,000 from Mercury. A extended warranty on a comparable MerCruiser is about 1/4 of that. So the manufacturer is expecting the outboard to cost 4 times more over the life of the extended warranty.

 

[Scott Danforth]

Muc, I have a entire 6.2 mercruiser with a single point drain on a pallet. there is not a single drain hose in that whole spider nest of spaghetti hoses that isnt plugged full of debris (rust, sand, rocks, shells, etc.) so if this boat wasnt in florida used year around, yes it would have frozen if someone were to winterize it.

 

[muc]

Muc, I have a entire 6.2 mercruiser with a single point drain on a pallet. there is not a single drain hose in that whole spider nest of spaghetti hoses that isnt plugged full of debris (rust, sand, rocks, shells, etc.) so if this boat wasnt in florida used year around, yes it would have frozen if someone were to winterize it.

Hi Scott, Please correct me if I make some wrong assumptions.
Someone bought a raw water cooled engine for use in saltwater. Even though MerCruiser offered freshwater cooling on this engine. And then didn’t do proper maintenance on it?
So because someone made a poor purchasing decision and then abused it, people should blame MerCruiser engineering?

The single point drain system was designed and marketed to extend the boating season in areas that have a possibility of overnight freezing temperatures. Before it came out I/O boaters needed tools and knowledge to use their boats in the early and late boating season.

I don’t agree that if someone was to winterize the engine you have it would have froze. Part of winterizing is flushing the engine to remove debris and replacing the water with the proper antifreeze. If you open a drain and no water comes out it would be a very good idea to find out why and correct it.

I see a few people on Iboats talk about how terrible the single point drain system is, and I wonder how much experience they have. I’ve winterized hundreds of them and talk to enough other mechanics that put the numbers into the thousands. I find it strange that none of us has seen a cracked block that was caused by a properly maintained single point drain system.

 

[Scott Danforth]

Muc, I know most of the engineers at Mercruiser.... Not a single one that I talked to personally supports the complexity of the single point drain.... the single point drain was requested by marketing

the only way to clear the lower block drain hoses is to remove the hose completely and rod it out. then you need to back-flush the block as the lower 2" of the block are now plugged with sand. at that point, you have spent 3 hours of labor to clear the hose and water jacket. the old 4/5 point or 7 point drain took 10 minutes

 

[wingless]

I don’t agree that if someone was to winterize the engine you have it would have froze. Part of winterizing is flushing the engine to remove debris and replacing the water with the proper antifreeze.

When I used to winterize my boat, it did not involve draining the raw water from the engines. It instead had the raw water pump draw the correct winterizing antifreeze into the raw water system, displacing the salt water.

There was zero issues using that method in all the years I setup the boat for a long cold storage.

 

[muc]

When I used to winterize my boat, it did not involve draining the raw water from the engines. It instead had the raw water pump draw the correct winterizing antifreeze into the raw water system, displacing the salt water.

There was zero issues using that method in all the years I setup the boat for a long cold storage.

Correct, you don’t have to drain it. You just have to make sure the entire system has the right antifreeze.

 

[muc]

Muc, I know most of the engineers at Mercruiser.... Not a single one that I talked to personally supports the complexity of the single point drain.... the single point drain was requested by marketing

the only way to clear the lower block drain hoses is to remove the hose completely and rod it out. then you need to back-flush the block as the lower 2" of the block are now plugged with sand. at that point, you have spent 3 hours of labor to clear the hose and water jacket. the old 4/5 point or 7 point drain took 10 minutes

Scott, Then you can ask them about how the system was designed to keep water flowing through the drain hoses while the engine is running. This keeps sand and silt from building up in the block. The person who explained this to me was one of the people that designed and tested the single point drain system. He seemed rather proud of the system. Maybe he was one of the engineers that you don’t know?

So your telling me that the engines that you winterized with the single point drain system have 2” of sand in them? And the engines with plugs in the block have less? That’s the exact opposite of what we see here in Minnesota. I guess that’s the beauty of the internet, you get to learn how different things are in other places.

 

[Scott Danforth]

Muc, the last engine I delt with was marina maintained, rack strored and flushed prior to storage

The hoses are all plugged and the block has 2" of sediment.

 

[tank1949]

Awesome, thanks Scott!! Looks like Michiganmotorz will be my choice as the other two sell packs of 5 and I need 6. Michiganmotorz sells them singly.

I ditched the plastic ones after one broke. I suspected heat over a decade too its tole. I replaced with 1/2" ss and a lot of Teflon tape and o ring. Getting proper o ring was a *****.

 

[muc]

Muc, the last engine I delt with was marina maintained, rack strored and flushed prior to storage

The hoses are all plugged and the block has 2" of sediment.

Scott, and you feel that this was due to the single point drain?

 

[Scott Danforth]

Scott, and you feel that this was due to the single point drain?

the engineering on the single point drain is flawed. so yes. there is no way to keep the velocity up in the hoses enough to keep them clean. there isnt enough pressure in the system for it to ever work on anything other than city water.

the ID of the fittings screwed into the block are smaller than the incoming strainer in the system (the PS oil cooler). so they are a natural choke point in the system.

all it takes is one little bit of debris to slow the minute amount of velocity down and the stem quits draining sections. the reduced velocity then allows the debris to plug up the lines, leading to a false sense of the system working for those that use it.

 

[Lou C]

I think the difference in opinion on the single point drain is a function of fresh vs salt...keeping in mind...fresh water boaters will often say...replace manifolds and elbows? Why....they never corrode enough! Well...here in the salt pond...they corrode enough that you will have to replace them most likely by 7 seasons...if you want to avoid getting water in the cyls via a rusted manifold, elbow or compromised gasket surface between the 2 (esp wet style exhaust). So now imagine how many rust flakes you will get in the block/heads of a cast iron engine in that environment...so much so...that it is very common...to have a cool running issue...that all we salt boaters know...is a piece of rust in the 'stat keeping it from closing....
After perusing a number of used late model boats...what I've found is that the %age of buyers who opt for closed cooling is surprisingly low. It is not commonly found on lower priced sport boats, usually only on bigger twin engine boats where the cost factory is a much smaller percentage of the total price. SO....most late model Merc boats are stuck with the single point drain system here, rust flakes and all. For sure even with conventional drain plugs you always have to rod out the block drains. Of the 4 drains, 2 on the engine and 2 on the manifolds...I always had at least 2 that were clogged.

 

[Scott Danforth]

a closed-cooled re-man 6.2 is $3k more than a raw water cooled

that is for a $680 heat exchanger, a $100 bracket, and a few hoses.

Merc wont honor the warranty if you buy a raw-water cooled motor and add a heat exchanger (even though its the exact same HX)

and it has a 5 week lead time.

per the broker now listing the boat, the added expense of the HX would not have translated into that much more money. the big thing is the "new engine and 3-year warranty"