Yanmar 4JH4E Overheating (at least the gauge says this...)

[solecollector]

I'm one step away from getting a mechanic to come checkout the engine - ! Hopefully I can get a few ideas from the masters on this forum.

I have a 2006 Yanmar 4JH4E with 800 hours on it. The boat was well taken care of - engines are super clean - previous owners were in their 80s and didn't use it much but took really good care of it. The one thing they said - the starboard engine always ran hotter than the other.

So here is the story. We took the boat out for a sea trial and the alarm went off for overheating. We saw water coming out of the exhaust and let it idle for a few seconds before shutting it down. There was no steam and even though the gauge was pegged at 240, it didn't seem that hot.

On the list of things to fix before we took possession of the boat was this overheating situations. Of course - we had the same problem again the first day when started our journey home from St. Pete to Key Largo. We found the overheating alarm only went off when we had the RPMs over 2,000. We also noticed that on the second day that we had to use more throttle at the controls for the same RPMs as the port engine - which wasn't the case before.

So we run the engine at lower RPMs (1,200 to 1,500) and had no problems until we needed her and went up on the RPMs and the alarm would go off. We get back home a few days later and I start to trouble shoot.

The owner's mechanic looked at the engine after the sea trial and said that he pulled the impeller and it looked fine - checked the other normal items and everything checked out. I assume he didn't take her out or run it over 2k.

When I started to trouble shoot it the first thing I did was pull the impeller. I was so hoping this was the problem - but to be honest - it looked brand new. I installed a new one anyway and put the old one in the spare parts bin. I then took off the hose going from the impeller to the block - started up the engine - water came gushing out. I then took the hoses off the block to the exhaust elbow (there are two hoses that go through a little gizmo on the wall - unsure what it is - but I am sure you guys do) and ran a hose through it - no problem - water streamed out. I then ran water upstream from the hose near the exhaust to through the heat exchanger towards the impeller... crud came out - but nothing crazy - and water did flow through. I had the hose at 40% or so. Also dove on the SD and cleaned all the holes - there was a lot of growth in just 3 weeks.

I was hoping that a few impeller blades or something would shake free but nothing really came out that could have stopped it up - or at least it didn't seem substantial to me.

I cranked up the engine - some water came out but when I went back to idle - nothing. I had to turn the boat around and ran the engine - no water at all. The heat gauge didn't go past 120 so it wasn't that warm (flipped the boat around pretty quickly - 5 mins or so). Turned it off. Let it set for a few hours. Turned it back on - nothing.

Now I know the impeller is fine. I know the hoses are clear. I assume the heat exchanger is good - but not positive. So could it be the thermostat?

Any ideas would be great! Sorry for the book....._steve

[mikepmtl]

Post a video of the amount of water coming out at 2000rpm.

And if you have an infrared temperature gun (very handy to have) take some readings at different areas of the engine after it has run for a while.

[rebel heart]

Maybe try T'ing into another salt water intake source for a bit and see what comes out of that? Or even shut the thru hull, put the hose in a bucket of sea water, and see if it sucks that up at idle?

I think you just need to fault localize. No water at idle means something is up for sure.

I don't know if you mentioned the sea water strainer? Something might really be gummed up somewhere.

[mikepmtl]

Rebel, that was what I was thinking as well (Strainer).
I think the most likely problem generally is lack of water flowing.

And although pulling the hose might seem like a lot of water, it might not be as much as is needed.

[YourBOATDoctor]

Hi Steve--Is the color of the coolant green or red? Im going to place my chips on the coolant being the culprit--but I would call a Yanmar tech and be sure since I would be making you do a lot of work if I am dead wrong. But I am willing to put some good chocolate on it that here lies the problem. Ive had this issue come up on other Yanmars, same alarm going off at higher rpms and it ended up all caused by the owners using the wrong anti-freeze. Per the manufacturer on those-it must be the long acting red coolant-Dexcool and nothing else. The green stuff results in prohibiting heat from transferring b/c it leaches silicates and then starts putting a coat on the interior surfaces of the system and as a result, reduces thermal transfer. Now if it is indeed red—then check the condition of it with a cheap antifreeze tester……it may be completely ineffective and need to be emptied and refilled.
'
The Dexcool is a rather pricey but a long life orange-red coolant. The specs on type can be found here: Sailboat Supplies, Engine Parts and Boat Parts . I double checked that your engine does also require this coolant type.

Unfortunately if its got the green stuff you will have to flush the system thoroughly of all on the freshwater side Good news, is those engines are pretty easy as they have accessible drain taps on the engine. Ive used a ¼ tube to go from nipple to container. Make sure you get all the drains drained. The manuals are on line and have diagrams.
.
also—if you also have a water heater run through the engine=there are a couple hoses that needs to also be cleaned that circulates coolant usually filled with dirt. A wet vac blower does a good job of blowing the stuff out.


Flush through with distilled water after draining, and then after than refill with Dexcool. That has solved my problems twice. But check with a Yanmar tech if this sounds about right to be sure so I don't send you astray . A phone call has saved me lots of wrong tree climbing myself




v
cheers
Lori

[Bash]

Originally Posted by solecollector

The owner's mechanic looked at the engine after the sea trial and said that he pulled the impeller and it looked fine - checked the other normal items and everything checked out. I assume he didn't take her out or run it over 2k.

Really? Was this "mechanic" the owner's brother-in-law?

You don't pull the impeller on an overheating boat without changing it. That would be tantamount to draining the oil and then saying, "It looked fine, so I put it back in."

[dannobee]

Well, the good news is that you have a perfectly good running engine on the other side to compare flow rates and temperatures with the Infra Red gun.

Is the water flow on THAT engine similar to the one experiencing the overheating?

[solecollector]

YourBOATDoctor - thanks for the very insightful reply. I will check today.

Bash - I think a lot of people inspect impellers and put them back - not saying it is the right thing to do.

dannobee / mikepmtl - I was at NAPA and they had a infrared temp gun but it was $99 so I bought one on Amazon for $28 that had really high ratings. Have to wait for it to come in.

rebel heart - I cleaned the heck out of that SailDrive - tons of growth in those little inlets. Unsure if they grow further back than a screwdriver can get. The one thing that did work was to put the hose from the impeller into a bucket and turn it on - water flowed quickly.

Love this community - thanks for all of the great advice. As soon as I get this fixed or have more questions I'll be back right here!

[senormechanico]

If the water from the bucket flowed quickly, put a dock hose in there to keep the level up in the bucket.
Take notes of volume of water coming out of exhaust at different RPM's.
Reconnect intake to thruhull and compare.
If it's noticeably different, the problem lies between your hose connection and the thruhull (if equipped) screen.
Mollusk growing in thruhull?
If it's the same, look upstream of the hose connection.

[YankeePSC34]

You have done a great job to find the culprit on the seawater side. I believe the freshwater cooling circuit should be checked too. Impeller in fresh water pump, thermostat, temperature sensor. You could swap components between the two engines to zero in on/eliminate possible sources.

[bstreep]

Normally, I'd look at the "normal" stuff: impeller, coolant type/quantity (50% MAX), etc. But, you have a pretty serious problem - 2,000 rpms? Your prop and bottom are clean, right? Prop spins freely?

I think at this point, you'll need to pull the heat exchanger. It SHOULD be easy, if your engine isn't a turbo. If it's a turbo, I think you'll need to pull that first. It's a total pain in the tail, but I can get mine off in about an hour and a half. Pull the end caps on the heat exchanger. You might get "lucky" and find parts from an old impeller just sitting there. This happens quite often... You can tap out the heat exchanger, and have a radiator shop "boil and rod" it. You will need new gaskets.

If you have a turbo, make sure it is working properly (do NOT use compressed air to spin it!). It should spin freely - and it can contribute to the problem.

[YankeePSC34]

I would check the thermostat first. Yanmar Service Manual:
....it should be inspected every 500 hrs and before this IF THE COOLING TEMPERATURE RISES ABNORMALLY.

[Dennis.G]

If talking a closed cooling system (with seawater heat exchanger) the seawater flow should always be present when engine is running. Should flow more at higher RPM, but should flow well at idle. The thermostat only controls the flow of the closed coolant system and does not effect seawater flow. If you do not see flow of sea water with engine at idle you have an issue in your seawater side. Don't worry on coolant side till seawater side is all good.

[sailorboy1]

make sure that the hose isn't getting and kinks in in once you install covers/floor boards etc.

There could well be too much antifreeze in the system since the overheat doesn't start until you put a larger load on it. If there is too much anti-freeze the coolant heat transfer is less and would not be able to handle the engine heat regardless of raw water flow after a point.

[Arcady]

Originally Posted by YourBOATDoctor

Hi Steve--Is the color of the coolant green or red? Im going to place my chips on the coolant being the culprit--but I would call a Yanmar tech and be sure since I would be making you do a lot of work if I am dead wrong. But I am willing to put some good chocolate on it that here lies the problem. Ive had this issue come up on other Yanmars, same alarm going off at higher rpms and it ended up all caused by the owners using the wrong anti-freeze. Per the manufacturer on those-it must be the long acting red coolant-Dexcool and nothing else. The green stuff results in prohibiting heat from transferring b/c it leaches silicates and then starts putting a coat on the interior surfaces of the system and as a result, reduces thermal transfer. Now if it is indeed red—then check the condition of it with a cheap antifreeze tester……it may be completely ineffective and need to be emptied and refilled.
'
The Dexcool is a rather pricey but a long life orange-red coolant. The specs on type can be found here: Sailboat Supplies, Engine Parts and Boat Parts . I double checked that your engine does also require this coolant type.

Unfortunately if its got the green stuff you will have to flush the system thoroughly of all on the freshwater side Good news, is those engines are pretty easy as they have accessible drain taps on the engine. Ive used a ¼ tube to go from nipple to container. Make sure you get all the drains drained. The manuals are on line and have diagrams.
.
also—if you also have a water heater run through the engine=there are a couple hoses that needs to also be cleaned that circulates coolant usually filled with dirt. A wet vac blower does a good job of blowing the stuff out.

Flush through with distilled water after draining, and then after than refill with Dexcool. That has solved my problems twice. But check with a Yanmar tech if this sounds about right to be sure so I don't send you astray . A phone call has saved me lots of wrong tree climbing myself

v
cheers
Lori

Agreed. This has been my experience too. Use of the correct antifreeze in conjunction with distilled water makes a huge difference.