Overheating Issue

[MarkVon]

Hi Everyone, I’ve learned a lot reading other threads and hugely appreciate your willingness to share knowledge and support each other.

I have a 1973 Ericson Mk II with an atomic 4 that is new to me as of last summer. I’m having issues with over heating. It stays at 170F at about 2.5 kts in speed (sorry my tachometer is not working). If I go any faster it starts to over heat.

Water coming out of the exhaust has decent flow but is NOT hot when the engine starts to overheat (180+ degrees).

The coolant also doesn’t seem to get that hot.

The engine has a heat exchanger and I would appreciate any suggestions tips as to where to start in solving this issue. I’m assuming I should be able to get my boat up to 5+ kts using an atomic 4, right?

Pictures attached.

[Dave Neptune]

How long since the HX was flushed or cleaned?

Did you check the impeller and the belt driving the HX pump? If you are loosing water flow after warming you may just have a compromised impeller.

Did the overheating sneak up over a few uses or all at once?

Dave Neptune

[Dave Neptune]

Oops

Mark(?), just saw your new. Welcome to the MMI forum!

Dave Neptune

[ronstory]

Yes, to pile on, welcome to the forum.

I noticed you didn't have a reservoir tank attached to the fill cap... is the engine topped off with coolant? Normally, if the engine is overheating there would be coolant coming out the relief port.

As Dave pointed out, you could have a compromised impeller. They are a wear item and since you have the handy-dandy MMI cover with the retained thumbscrews, you could drain the coolant and pop the cover and check the condition. Or just put a new one in, IMO never a bad idea. Ken has them for $36.

[MarkVon]

Thanks for getting back to me! It's so great to have knowledgeable folks willing to help. When I bought the boat the surveyor asked me, "Do you have a job?". I said "Yes!" and then he said, "Great, now you have two!"

As far as I know the HX was flushed before I bought the boat last summer. But maybe I should do it again? I assume there's a thread on this forum that tells me how to do it?

To clarify, water is flowing out the the exhaust, but the temperature of the water is not hot, even when it is over heating.

The overheating has been slowly getting worse since I got the boat.

I'm planning to order a new empeller for the MMI fresh water pump. Should I also do it for the raw water pump (which doesn't looke like an MMI pump)? Picture attached circled in red.

Because the exhaust water and coolant aren't getting hot, does this point to needing to do a flush? I've read about an acid or vinegar flush.. Thoughts?

[MarkVon]

Yes, the coolant seems to be topped up. The level is at about an inch below the cap.

[Dave Neptune]

Mark, the problem is the HEAT is not being exchanged. If you are getting water out the exhaust that's just a bit warm and a heated engine could be the t'stat if so equipped is sticking. If not it could be lack of block circulation (the pump) or the HX is scaled up and the heat is not exchanging.

If it is the HX try a vinegar lush first before getting to aggressive. Does the HX have a removable end for inspection?

Dave Neptune

[Surcouf]

my 2 cents:
- no coolant circulation at all: With engine cold, disconnect the coolant hose just before the heat exchanger, route it to a bucket and start the engine for a few seconds. The engine should drain the coolant into the bucket rather quickly. If it does not, you should check pump impeller first, eventually replacing it. If the impeller is OK, (first put the coolant back in the tank) try disconnecting at the discharge of the thermostat housing, and do same test to check for potential plugged manifold. (vinegar etc.. (good luck!))
- coolant circulation OK, but not in block: new thermostat may be required
- Coolant (really) circulates, but heat not removed... something is really wrong with your heat exchanger...

PS: seems that Dave said the same previously, just much better... my English is broken

[MarkVon]

Thank you both for getting back to me. I'm excited to learn more about the engine and appreciate your teachings.

I took it out again today to try to get a better handle on what was going on.

The heat exchanger is not getting hot. It feels like the raw water is flowing through and going out the exhaust fine, but something is stopping the heat exchanger system from playing a role.

I took the end cap off the larger bottom tank on the HX and didn't notice any build up. It looked like a clean empty tank.

In the first picture I've attached, do I have the correct hose circled in purple to remove so I can turn the engine and see what comes out (into a bucket)?

My next steps if nothing comes out of that hose will be to:

"check pump impeller, eventually replacing it. If the impeller is OK, (first put the coolant back in the tank) try disconnecting at the discharge of the thermostat housing, and do same test to check for potential plugged manifold."

If manifold is blocked, I'll remove the thermostat cap and check if it has a thermostat and whether it's working. Then I'll do a flush of the manifold - acid or vinegar?

Any other thoughts appreciated! I'll keep you updated.

[Surcouf]

Yes the purple is the discharge of the engine through the manifold. This is the first thing I would check, because it is just easier to do that that to open the pump to check the impeller (many check the impeller on a yearly basis as good practice, you may have to go there a one point anyway). For the thermostat, make sure to have a gasket in hand first, or worst case a sheet of paper gasket to cut and use on a temporary basis.

Regarding the type of cleaning, I let the more competent ones answer.

[Al Schober]

Other than the high reading on the gauge, is there any other symptom of overheating? I'm thinking the gauge/sender may be faulty.

[thatch]

Hi, I agree with the others that there is a flow problem on the coolant side of the engine. In an tight installation like this, I would tend to look for the easiest things to check first. Since the coolant side water-pump is reasonably accessible, I would remove both hoses from it and do a flow check using two short lengths of spare hose into a bucket of water. If it does pump water, I suspect, as Dave mentioned, that the thermostat may be malfunctioning and routing the coolant around the block. In general, coolant tends to keep the water passages pretty clean, however, in raw water engines that have been converted to FWC, there is always a possibility that some residual "cornflakes" may still be roaming around.
Tom

[Dave Neptune]

Mark, does your A-4 have a t'stat? If you do remove it, if your not sure check to see. You can check to see if the t'stat is INSTALLED by removing the little plug on the top and check or poke around. If it is not there put the plug back in, if it is there remove it and test it.

The "corn flakes" that thatch is referring to are the scaly rusty deposits that break away after flushing. these "corn flakes" tend to gather in tight spots and will plug those spots partially or even completely. First place to check for these is the water exit fitting on the manifold. Remove the hose and fitting so you can see under it. This is quite common after flushing.

Tom, I like the "corn flakes" comparison .

Dave Neptune

[Dave Neptune]

Mark, is your MkII a 35? I had one for 34 years #136.

Dave Neptune

[MarkVon]

Wow, thanks everyone.

A few more questions and thoughts:

1) I'm going to start with removing the hose (marked in purple above). Do I just need to turn the engine over to see if anything comes out? Or do I actually start the engine? I'm going to be doing this by myself, with the ignition key in the cockpit. Do I need a special sealant or tape for disconnecting and connecting hoses or are they only held by the clamp?

2) I did suspect that the temperature guage was malfunctioning. When they guage says it's over heating, the block does seem hot, but I have no idea if it's normal or too hot. The guage can jiggle about and I'm not sure if that's normal. Is there a way to test to make sure it's working properly?

Are these the replacement parts for it:

Temperature Sending Unit: https://moyermarine.com/product/issp...2-gaug_10_179/

Guage: https://moyermarine.com/product/issp...ge-gaug_09_178

Do I need to replace the wire between these two products as well or use the wire that is already there? What wire should I use?

3) I don't know if it has a thermostat and I'm not sure how to check. Dave you said, "You can check to see if the t'stat is INSTALLED by removing the little plug on the top and check or poke around". I'm not seeing the 'little plug'.

Because the thermostat cover requires a gasket, I won't open it up until I order this thermostat and gasket. Does this make sense or can I make a suitable gasket?

https://moyermarine.com/product/mmi-thermostat-150-degree/

4) Fresh Water Pump: Sounds like I should order a new impeller whether I need it or not. The pump is in an awkward spot so I'd have to take it off blind. Any tips? Do I need any special tools? Picture attached below.

https://moyermarine.com/product/flexible-impeller-csob_02_63

5) I'm also planning to order this manual:

https://moyermarine.com/product/service-and-overhaul-manual

Anything else I should add to the order? Because I'm shipping to Canada I want to do it all in one shipment.


Mark

PS: Yes, it's a Ericson 35 Mk II. I love it and will love it more when I have this engine performing properly! What speed should I be able to comfortably go once I've solved the engine issues?