Seacore Engine Overheat

TonyG13

My son and I were having a great morning. Slept overnight, then got up before dawn to head out to watch the sunrise. Waves were less than 1 foot, and calm winds.

We left the harbor, and throttled up cruising between 28-30mph at ~3500rpm. Went out about 3 miles then backed it down to idle for the sunrise. Then throttled back up again to a different spot to get some pics from a different perspective. Total time was about 30-40 minutes.

While at idle in open water the port engine alarmed with an overheat. Display showed 223F.

Shut down the engine and started heading back home. 

At the harbor mouth, turned the engine on and it showed 160, but then started shooting back up quickly.

Limped in to dock and shut everything down.

Bilge had orange anti-freeze - probably a few gallons. The Seacore overflow reservoir was basically at "cold" level, but it appeared the antifreeze also sprayed out from radiator cap. I did notice it appeared the cap was loose.

So the big question: What would be potential causes that I can look at - and how to diagnosis how/what happened?

Also, please remember my mechanical/engine knowledge is nothing near any of your levels, so I might ask follow-up questions that may seem stupid.

Handymans342

Water pump leak??

Handymans342

Impeller bad?

LaRea

You cruised at 3500 RPM with no issues, then it overheated at idle?  It probably means your seawater pump is kaput.

Assuming your 2014 boat has the original water pump:  The rubber impeller spins between two brass walls of the pump body.  Over time, debris such as sand can wear grooves in the brass.  Once that happens, water squirts through the grooves and the pump starts losing it's ability to pump. 

If so, a new impeller won't fix it.  Your pump is shot and must be replaced.  

They are expensive.  That's why some of us switched to the Hardin Marine water pump, which is cheaper and has replaceable stainless steel wear plates.  

YYZRC

Sounds to me like you lost a coolant loop hose or maybe a freeze plug. Not impossible that the overheat was initially caused by impeller failure though. 

212rowboat

Look at the hoses near the belt... there is chance one was rubbed... also look of one laid on hot manifold and melted... 

The radiator/exchange cap is a crucial part of the cooling system and they go bad.  It could be that simple.  When the system is open as opposed to closed the pressure from water/coolant turning to steam will blow right out the easiest place and that's usually the cap.... 

Check the hoses... get a new cap... 

223* is at the border of a bad uh-oh.... meaning gaskets are at risk.  Warped heads... ect... an engine can handle it most the time but its dangerous all the same above 215 AND an open system... a closed system (no coolant blow out/steam) can handle upwards of 250... 

The coolant shouldn't have boiled unless it was open somewhere... 14lbs radiator cap raises the boil point to 260ish degrees... so the system had to be opened somewhere... i hope for your sake it was open at the cap which is real easy to do.... just look at them wrong and they'll unseat.  

All that said, by all means check for a blockage at your sea pump or your sea pump failing... could be that just as easy. 

TonyG13

Thanks for everyone's input. I'm heading back to the boat now and will start looking around for anything obvious.

TonyG13

OK, I crawled around as best I could - which means not too much because there is no friggin' room anywhere to move my big butt around the engines. Anyway, I looked and felt hoses, connections, etc. and nothing seems amiss. Another than a lot of orange sprayed around the bilge.

So should I start small as @212rowboat suggested and get a new radiator cap -- and refill with DexCool. Would refilling and running at idle on the dock then show me a possible active leak? And if it's the impeller or pump, I could watch the temp and shut down quickly?

The MerCruiser manual I have says: "Add coolant only when engine is at normal operating temperature." Then add coolant through the recovery bottle.

So do I start the engine and fill through the recovery bottle or should I fill as much as I can through the radiator cap first - then start the engine and do more through the bottle?

Also, does anyone know how much DexCool I should be using in a full system (350 MAG SeaCore)? Another site says 20 quarts (4 gallons). Does that sound correct?

Black_Diamond

It is just like a car. Fill to the rad cap full. Adding more at the overflow is correct. The 4 gallons would be from empty. 

TonyG13

Thanks! I guess that'll be my first step.

Aqua_Aura

Fill it and let it run to see if there is any fluid spraying out from hoses or fittings. Also if you have never replaced the impeller you should probably do it as well. 

TonyG13

Aqua_Aura said:

 Also if you have never replaced the impeller you should probably do it as well. 

That's on the back of my mind. When we bought the boat two years ago part of the deal was the broker was supposed to change the impellers as well as a bunch of other stuff. After we took possession and started to really go over the boat, we noticed some "shortcuts" that the broker took on other things to get the boat ready for sale. So I'm beginning to wonder if they truly did the work. (And it's one of those things that you really can't check unless you stand watch over them.)

aero3113

Funny you say that @TonyG13 . I feel that whenever I have someone do work for me I need to watch over them. I feel like they will try to take shortcuts or just do it wrong. When we had our pool built they put the diving board supports in crooked and were ready to lay the pavers. I showed them how off it was and told them to redo it, they had to take out the jack hammer. When they redid it I was over their shoulder, I even took out my level. You feel like a d&$k but your paying good money and want it done right. I didn’t realize my wife was taking pictures of me, LoL! 

Aqua_Aura

aero3113 said:

Funny you say that @TonyG13 . I feel that whenever I have someone do work for me I need to watch over them. I feel like they will try to take shortcuts or just do it wrong. When we had our pool built they put the diving board supports in crooked and were ready to lay the pavers. I showed them how off it was and told them to redo it, they had to take out the jack hammer. When they redid it I was over their shoulder, I even took out my level. You feel like a d&$k but your paying good money and want it done right. I didn’t realize my wife was taking pictures of me, LoL! 

That is me for sure. I do most of my work myself but when I do hire someone,which is very rare I watch them like a hawk. Mechanics I am less concerned with but when it comes to contractors they are the worst. 

aero3113

Is frustrating, especially when you know how it should be done. When you pay someone it should be done as expected or better!

Aqua_Aura

When I removed some walls in my Arizona house it was summer time so I hired someone to deal with all the electrical in the attic since it was so hot. The first thing they accomplished was going up my attic stair and stepping directly on the drywall and not the joist. Put his foot right through it. 

J3ff

aero3113 said:

Funny you say that @TonyG13 . I feel that whenever I have someone do work for me I need to watch over them. I feel like they will try to take shortcuts or just do it wrong. When we had our pool built they put the diving board supports in crooked and were ready to lay the pavers. I showed them how off it was and told them to redo it, they had to take out the jack hammer. When they redid it I was over their shoulder, I even took out my level. You feel like a d&$k but your paying good money and want it done right. I didn’t realize my wife was taking pictures of me, LoL! 

This is like paying a mechanic $11,540 dollars to replace your outdrive, align the engine, replace the gimbal AND STILL HAVING A PROBLEM BACK THERE (sounds like a helicopter at times). I'm seriously considering throwing the boat on ebay for a starting price of 5000 dollars and walking away from it. This is after paying him almost 5000 dollars to remove the engine, find the problem with the transom leak, having him redo everything back there and then putting it back in. Also after 4500 spent trying to REPAIR the outdrive in the first place (fired that mechanic).  You don't know who to trust because all these guys are crappy at the job you are paying them good money to do! 

TonyG13

@YYZRC - Just to confirm  before I start filling with antifreeze -- when you say "freeze plugs" do you mean the blue drain plugs located around the engine? I found the diagram of where they all are, so I'm going to check that they are all indeed still there before filling. 

TonyG13

@LaRea - Been looking at the Hardin website and watched some YouTube reviews. Looks great. If it gets to that point, I will definitely invest it one. I just wish they had a SeaCore version (with pulley). I wonder why they don't.

LaRea

I thought SeaCore engines use the same water pump as other engines.  Am I wrong?

aero3113

If that’s the case, Harden sells the pump with the pulley.

https://www.hardin-marine.com/c-132-mercury-sea-pumps.aspx

TonyG13

Sorry. I meant Axius, which I have. The Hardin page says that model will not replace pulleys from Axius models as the diameter is not the same. But again, wondering why they don't offer an Axius pulley model.

YYZRC

I would check all those blue drain plugs, yes! I think you will find the source of the leak pretty quickly. The circulation pump (different from the impeller) pushes the coolant throughout the block. If the block is dry and the thermostat is closed it might take some time for the coolant to move into the block but @212rowboat is for sure the SME here. 

TonyG13

Still tracking down why I overheated. Admiral wants me to wait until during the week so she can at least sit and enjoy dockside before I start crawling around.

Anyway, is it true one way to quick check if the impeller is bad (without removing) is to spin it by hand with the serpentine belt off? If it spins freely - it's bad? And if it's got resistance, it's probably still working somewhat?

Aqua_Aura

Never heard that but it would make sense. The impeller fits tight in the housing and if it is destroyed then it would move with little to no resistance. It should be a constant resistance feel if it is intact. 

Here is a good video of how they operate. 

https://youtu.be/ECv1VwW6RTo

aero3113

If you test it that way, you won’t be able to tell if any vanes are missing. You can have one or two that broke off and still have resistance.

212rowboat

There are a bunch of tricks... but that is what they are.  

"Struggle and cuss, cuss and struggle; then you do what must be done."

You need to put eyes on that impeller.  You need to bend the blades and look for cracks.  You have it off you may as well replace it.  You need to confirm its intact and if it isnt you need to locate the missing parts.   Its not fun, but what is? Piece and peace of mind. 

davidbrooks

x2 on what 212rowboat said.  if you are missing any parts of the impeller then you will need to trace the water path too look for the pieces.  It is very easy for them to work their way through the system and cause all kinds of problems with overheating.  Time to pull the water pump.

TonyG13

Thanks guys. I have an OEM kit coming tomorrow. I'll probably order the Hardin version off-season to have it on hand for the next change.

TonyG13

OK, so here's a newbie question about impeller changing while in the water:

Since I have SeaCore, does that mean...

1. It's antifreeze being distributed through the impeller pump?
2. If yes, I don't have to worry about removing the hoses and flooding things?

Dream_Inn

That pump will have raw water coming thru it.  You will have to raise the hose coming from outdrive (upper hose on back of pump), to keep water from flowing in.