Mercruiser cooling system

[PapaT]

I just bought a 2006 27’ sundeck Sea Ray and.today i opened the engine compartment and water was gushing out of the cooling system drain. The blue plug threads deteriorated. So I’m buying a new plug and hopefully can clean the threads so the plug fits tight. Question- where and with what do i fill the system? The liquid that ran out was purely clear and had no smell- i guess it was plain water? Thanks for any help

 

[Strecker25]

I just bought a 2006 27’ sundeck Sea Ray and.today i opened the engine compartment and water was gushing out of the cooling system drain. The blue plug threads deteriorated. So I’m buying a new plug and hopefully can clean the threads so the plug fits tight. Question- where and with what do i fill the system? The liquid that ran out was purely clear and had no smell- i guess it was plain water? Thanks for any help

That side of your cooling system is cooled be raw water, sucked up through the outdrive on the boat. The entire engine is cooled by raw water, including the block, fuel, exhaust, and power steering coolers

no need to refill it, the impeller will do that for you. I would suggest keeping a couple of those blue plugs onboard. They tend to break

as an aside, those plugs are there as part of the winterization process so you’re able to drain the raw water out of the system prior to winter layup if required in your area.

 

[PapaT]

That side of your cooling system is cooled be raw water, sucked up through the outdrive on the boat. The entire engine is cooled by raw water, including the block, fuel, exhaust, and power steering coolers

no need to refill it, the impeller will do that for you. I would suggest keeping a couple of those blue plugs onboard. They tend to break

as an aside, those plugs are there as part of the winterization process so you’re able to drain the raw water out of the system prior to winter layup if required in your area.

Wow that makes me feel better. So just put in a new plug and run the engine and it will be ok? Thanks so much

 

[Bill Curtis]

If you want to never have to worry about a blue plug breaking off again (which they will), these Stainless Steel ones are available.

https://www.hardin-marine.com/p-810...mercruiser-22-806608a02-8m2000874-5-pack.aspx

 

[Fill Ess]

I replace them every year. I know it's overkill, but I've also had broken ones like you and it can be a real PITA.

I also keep a bag on board just in case.

There are different kinds/brands out there and I've found that the deeper blue OEM Merc ones are the best. It seems like the O-rings in the aftermarket (lighter blue) ones don't seal as well .... or maybe I got a bad batch?

 

[Lazy Daze]

Side note, those plugs eventually fail due to heat. Good design, but heat gets to them. They seal with an o-ring - which you'll see - just snug 'em up is all that's needed. You should replace the others while you're at it. I'd recommend doing it about every 5 years for good measure.

 

[PapaT]

If you want to never have to worry about a blue plug breaking off again (which they will), these Stainless Steel ones are available.

https://www.hardin-marine.com/p-810...mercruiser-22-806608a02-8m2000874-5-pack.aspx

Thanks, great idea

 

[PapaT]

Side note, those plugs eventually fail due to heat. Good design, but heat gets to them. They seal with an o-ring - which you'll see - just snug 'em up is all that's needed. You should replace the others while you're at it. I'd recommend doing it about every 5 years for good measure.

Thank you, i plan to replace the other one

 

[PapaT]

I replace them every year. I know it's overkill, but I've also had broken ones like you and it can be a real PITA.

I also keep a bag on board just in case.

There are different kinds/brands out there and I've found that the deeper blue OEM Merc ones are the best. It seems like the O-rings in the aftermarket (lighter blue) ones don't seal as well .... or maybe I got a bad batch?

Thanks, I’m planning to order some the stainless steel

 

[Lazy Daze]

You may have 2 more on your raw water pump.

Heat up a large flat blade screwdriver to make a new "slot" in the remaining piece still inside the hole.

The only thing I wonder about regarding the SS ones... I wonder if there's ever been a problem removing them due to galvanic corrosion? That's the thing I like about the nylon ones - removal is always easy.

 

[PapaT]

You may have 2 more on your raw water pump.

Heat up a large flat blade screwdriver to make a new "slot" in the remaining piece still inside the hole.

The only thing I wonder about regarding the SS ones... I wonder if there's ever been a problem removing them due to galvanic corrosion? That's the thing I like about the nylon ones - removal is always easy.

Thanks for info. I also thought about corrosion with the steel ones. The plugs aren’t expensive, I’ll just replace them more often.

 

[PapaT]

Thanks, I’m planning to order some the stainless steel

Well I decided to continue using the blue plugs, but thanks for the idea

 

[Lazy Daze]

Just for full transparency, I've never used the SS ones - I've certainly used SS bolts, though! My comment was just a "wondering out loud" comment. I do know that the blue ones are always easily removable... until they get brittle and break!

 

[PapaT]

Just for full transparency, I've never used the SS ones - I've certainly used SS bolts, though! My comment was just a "wondering out loud" comment. I do know that the blue ones are always easily removable... until they get brittle and break!

Ok thanks

 

[PapaT]

That side of your cooling system is cooled be raw water, sucked up through the outdrive on the boat. The entire engine is cooled by raw water, including the block, fuel, exhaust, and power steering coolers

no need to refill it, the impeller will do that for you. I would suggest keeping a couple of those blue plugs onboard. They tend to break

as an aside, those plugs are there as part of the winterization process so you’re able to drain the raw water out of the system prior to winter layup if required in your area.

So after I replace the plug and run the engine so the pump pulls in water, how will I know the system is full and I can take the boat for a drive?

 

[Lazy Daze]

So after I replace the plug and run the engine so the pump pulls in water, how will I know the system is full and I can take the boat for a drive?

It doesn't "fill" like I think you're thinking. Water constantly moves through the system and back out. You don't need to do anything or wait any particular time. Start her up and go.

FYI, replacing the lower plugs while in the water... you may start siphoning the ocean into your boat. But don't worry, it will be a whole lot less water than you think. But if you break off a plug that's down low, that could be an issue. I'd suggest putting the boat back on the trailer for this.

 

[PapaT]

It doesn't "fill" like I think you're thinking. Water constantly moves through the system and back out. You don't need to do anything or wait any particular time. Start her up and go.

FYI, replacing the lower plugs while in the water... you may start siphoning the ocean into your boat. But don't worry, it will be a whole lot less water than you think. But if you break off a plug that's down low, that could be an issue. I'd suggest putting the boat back on the trailer for this.

Thank you, you’ve been very helpful and saved me from calling a mechanic. Cool

 

[Bill Curtis]

I've have / had the S/S plugs on my last 2 boats (both big Block Bravos) and have not had a problem in the past 6 or 7 years.

I have / had the Hardin S/S raw water pumps on them too.... No problems.

 

[PapaT]

I've have / had the S/S plugs on my last 2 boats (both big Block Bravos) and have not had a problem in the past 6 or 7 years.

I have / had the Hardin S/S raw water pumps on them too.... No problems.

Thanks good to know