5.0 MPI manifold t-drain failure

[Anthonyexeter]

Fitted new manifold/risers and new t-drain manifolds. First trip out and the starboard bowl on the t-drain blew off and flooded the bilge. What could cause this? Faulty part? Popped it back on and made it to the mooring at slow speed. Is this part of the single drain system? Can it be easily deleted? Seems like a potential weak point just a plastic bowl press fit into a metal tee.

 

[AllDodge]

Is this part of the single drain system?

I think your talking about the check valve, and if so look for the ball in your bilge

Can it be easily deleted?

It can be removed but you need to remove all of the single point system and convert to 5 to 7 point system

Would need your serial number to determine what would be needed

 

[Anthonyexeter]

I think your talking about the check valve, and if so look for the ball in your bilge

View attachment 36979


It can be removed but you need to remove all of the single point system and convert to 5 to 7 point system

Would need your serial number to determine what would be needed

Yeah. That's the part. The plastic bowl detached and filled the bilge. It was a new part straight out of the box. I'm guessing the ball floats and when the engine is running the pressure keeps the check valve closed. If I'm looking at the circuit diagram right all I'd have to do is swap them for the screw in cap versions, add drain cocks to the block and replace the lower draining manifold where the hoses meet with a hose.

 

[AllDodge]

Yeah. That's the part. The plastic bowl detached and filled the bilge. It was a new part straight out of the box. I'm guessing the ball floats and when the engine is running the pressure keeps the check valve closed. If I'm looking at the circuit diagram right all I'd have to do is swap them for the screw in cap versions, add drain cocks to the block and replace the lower draining manifold where the hoses meet with a hose.

Maybe, I'm not seeing how your system was done, there are a few different ones

 

[Anthonyexeter]

This is the offending part that disassembled itself. I grabbed the old ones out of the bin and they seem like OEM parts and much better. I'll probably put them back. The bowl just clipped back on. The original 2 on the bench are much more solidly built.

 

[louc]

Mercruiser has done some good things with their exhaust/cooling systems (dry joint manifolds) and bad (too many parts made of plastic that should be metal)! Good thing you caught it. I'd sh!t can all the easy drain stuff and use simple metal manual drains. Harder to reach, but easy to rod out if they don't drain.

 

[Bt Doctur]

Personally I remove those systems and revert back to the old school drains including the block drains. Reason being the block ones rust/sand/corrode closed and crack the block
Also called "the quick crack system"

 

[Anthonyexeter]

Mercruiser has done some good things with their exhaust/cooling systems (dry joint manifolds) and bad (too many parts made of plastic that should be metal)! Good thing you caught it. I'd sh!t can all the easy drain stuff and use simple metal manual drains. Harder to reach, but easy to rod out if they don't drain.

Glad I caught it when I did. Had a momentary dip in revs. Stopped, lifted the lid and water was just touching the water pump and spraying everywhere. I'll try and convince the owner to strip out the single point drain. It's a cramped engine room but should be able to get to all the original drain points. Guessing some little bronze ball valves in the block would be the best thing. Pinned ones so they can't accidentally open.

 

[louc]

Better to use a removable drain plug so you can rod the hole out if it doesn’t drain. When cast iron rusts it flakes off and that clogs drains.

 

[Anthonyexeter]

Better to use a removable drain plug so you can rod the hole out if it doesn’t drain. When cast iron rusts it flakes off and that clogs drains.

Just thought a full flow ball valve would be just as easy to rod with a cable tie

 

[louc]

As long as you can rod it then yes. Iron blocks were intended to be used with antifreeze with corrosion inhibitors this is why in raw water cooled applications they become a headache and Merc tried everything BUT doing the RIGHT thing, make at least a half closed cooling system standard (cools block/heads only will work with the Alpha impeller). I would never install a new or reman engine in my own boat without it.

 

[Dieter]

This is the offending part that disassembled itself. I grabbed the old ones out of the bin and they seem like OEM parts and much better. I'll probably put them back. The bowl just clipped back on. The original 2 on the bench are much more solidly built.

this may have come apart from freeze damage. If you put it away last fall and it was working fine, then in spring it popped apart I would wonder if the system was fully drained

 

[Anthonyexeter]

this may have come apart from freeze damage. If you put it away last fall and it was working fine, then in spring it popped apart I would wonder if the system was fully drained

No. It was new. Replaced the riser and manifold last week with new t drain. Less than 20 mins runtime

 

[Anthonyexeter]

As long as you can rod it then yes. Iron blocks were intended to be used with antifreeze with corrosion inhibitors this is why in raw water cooled applications they become a headache and Merc tried everything BUT doing the RIGHT thing, make at least a half closed cooling system standard (cools block/heads only will work with the Alpha impeller). I would never install a new or reman engine in my own boat without it.

I'm a diesel guy. Been working commercial boats for 40 yrs. Only doing this for a friend. Just find everything infuriating on these. Everything from the ridiculous mounting of the raw water pump to the inaccessible fuel cooler that needs the engine out to get to it because it's tight against the engine beds.

 

[louc]

I/Os made more sense when they were simple GM inboard engines with carbs and none of this extra nonsense. I have one of those so I can tolerate it. This is also why outboards predominate now. Yes they are very expensive but you pay the big price to start, but your yearly maintenance is a lot less. Draining? Just put the motor down!
I also blame the dumb fools running boat companies. It is just as easy to make a wide open engine compartment with everything accessible as it is to pack the back of the boat with all the cushy seats in the way. Older I/O boats often had a simple dog house over the engine and 2 jump seats one on each side, those were easy to service. Oh but that's not cool enough for today's spoiled boat buyers!
My brother bought a 2020 Chapparal with a 4.5 Merc I/O. I looked it over told him to wait for an outboard. He bought it. I maintained it for a few years. I showed him where the starter is (buried) and the steering actuator is (buried) to replace either the engine comes out. Easy drain system works for a few years in salt then clogs. The first time it overheated because marine growth clogged the water intakes, he had had it. I said ready for the outboard now lol? He traded it on a new boat, same model with a Yamaha 4 stroke!

 

[Anthonyexeter]

I/Os made more sense when they were simple GM inboard engines with carbs and none of this extra nonsense. I have one of those so I can tolerate it. This is also why outboards predominate now. Yes they are very expensive but you pay the big price to start, but your yearly maintenance is a lot less. Draining? Just put the motor down!
I also blame the dumb fools running boat companies. It is just as easy to make a wide open engine compartment with everything accessible as it is to pack the back of the boat with all the cushy seats in the way. Older I/O boats often had a simple dog house over the engine and 2 jump seats one on each side, those were easy to service. Oh but that's not cool enough for today's spoiled boat buyers!
My brother bought a 2020 Chapparal with a 4.5 Merc I/O. I looked it over told him to wait for an outboard. He bought it. I maintained it for a few years. I showed him where the starter is (buried) and the steering actuator is (buried) to replace either the engine comes out. Easy drain system works for a few years in salt then clogs. The first time it overheated because marine growth clogged the water intakes, he had had it. I said ready for the outboard now lol? He traded it on a new boat, same model with a Yamaha 4 stroke!

Oh god yes, the starter motor. You'd have to break your spine in 3 places to contort into a position to remove that. I've warned my friend if the starter goes I'm changing my phone number.

 

[Mark S.]

this may have come apart from freeze damage. If you put it away last fall and it was working fine, then in spring it popped apart I would wonder if the system was fully drained

This is exactly what happened to my 5.0 MPI. First start in spring water was shooting out. It was a blessing actually because it fixed my vapor lock problem whereby the malfunctioning valve was allowing hot engine water to back up into cool fuel module. After this I started leaving my single point drain valve open all winter and pulling the quick disconnects on each side of the lower block. This has worked perfect for 23 seasons but I am in freshwater.

 

[Anthonyexeter]

This is exactly what happened to my 5.0 MPI. First start in spring water was shooting out. It was a blessing actually because it fixed my vapor lock problem whereby the malfunctioning valve was allowing hot engine water to back up into cool fuel module. After this I started leaving my single point drain valve open all winter and pulling the quick disconnects on each side of the lower block. This has worked perfect for 23 seasons but I am in freshwater.

I'm hoping the issue was actually just a faulty new part. The build quality difference from the original OEM ones I took off to the new clone ones I put on was shocking. Didn't really pay much attention when changing them but side by side after the failure the old ones were nice tight fit bowls but the new ones popped off as easy as tops on an aerosol can.