AAAAARRRRRRGGGGHHHHHH. Overheating AD31 Again!

[FalconSteve]

Hi all,

Just bought MERLIN back to ocean village from Shamrock Quay where she had been out of the water having her bum painted and sterndrives serviced, I couldn't believe my eyes when the starboard temperature started rising higher and higher, surpassing the 95 degrees that caused me my problems last year. Now the temperature rose all the way to 110 degrees and to make matters worse the engines weren't even running past 1500 rpm.

Last year the overheating occurred only when the engine was under significant load, and dissipated when the boat was reduced to displacement speed.

I checked the usual suspects when she was on her home berth, impeller was rotating and whole, water was moving through the raw strainer filter and pumping out with some force when the lid was removed and the engine turned over. I had checked that water was exiting the sterndrive at Shamrock Quay, both engines were operating correctly. Then I checked the fresh water side and the thermostats were both open when I removed the cover and the water level was ok before I set off (obviously I lost water when I removed the thermostat cover). My current thinking is that the freshwater pump may be faulty, I am seriously contemplating getting a professional engineer involved now, I am completely fed up with the whole thing now. I hate having to do this, I like to rely on my own skills whenever I can, but this is clearly beyond me .

 

[powerskipper]

we had a anode that had broken off in the engine itself and was causing a blog age at low speed. or the Pump was giving up the ghost and not pumping strongly enough to cope with engine requirements.

 

[Elessar]

Hi all,

Just bought MERLIN back to ocean village from Shamrock Quay where she had been out of the water having her bum painted and sterndrives serviced, I couldn't believe my eyes when the starboard temperature started rising higher and higher, surpassing the 95 degrees that caused me my problems last year. Now the temperature rose all the way to 110 degrees and to make matters worse the engines weren't even running past 1500 rpm.

Last year the overheating occurred only when the engine was under significant load, and dissipated when the boat was reduced to displacement speed.

I checked the usual suspects when she was on her home berth, impeller was rotating and whole, water was moving through the raw strainer filter and pumping out with some force when the lid was removed and the engine turned over. I had checked that water was exiting the sterndrive at Shamrock Quay, both engines were operating correctly. Then I checked the fresh water side and the thermostats were both open when I removed the cover and the water level was ok before I set off (obviously I lost water when I removed the thermostat cover). My current thinking is that the freshwater pump may be faulty, I am seriously contemplating getting a professional engineer involved now, I am completely fed up with the whole thing now. I hate having to do this, I like to rely on my own skills whenever I can, but this is clearly beyond me .

is the exhaust staying cool?

if not its a raw water problem, if it is it's fresh.

if it's fresh, check thermostat and coolant pump. On mine the coolant pump was spinning on the shaft, but this was only noticeable on the bench with a bit of force behind it.

 

[superheat6k]

If its the freshwater could you have an airlock preventing flow. On my VP TAMD60 I have to vent the system, especially at the turbo charger, where the vent point is obscured.

 

[volvopaul]

Hi all,

Just bought MERLIN back to ocean village from Shamrock Quay where she had been out of the water having her bum painted and sterndrives serviced, I couldn't believe my eyes when the starboard temperature started rising higher and higher, surpassing the 95 degrees that caused me my problems last year. Now the temperature rose all the way to 110 degrees and to make matters worse the engines weren't even running past 1500 rpm.

Last year the overheating occurred only when the engine was under significant load, and dissipated when the boat was reduced to displacement speed.

I checked the usual suspects when she was on her home berth, impeller was rotating and whole, water was moving through the raw strainer filter and pumping out with some force when the lid was removed and the engine turned over. I had checked that water was exiting the sterndrive at Shamrock Quay, both engines were operating correctly. Then I checked the fresh water side and the thermostats were both open when I removed the cover and the water level was ok before I set off (obviously I lost water when I removed the thermostat cover). My current thinking is that the freshwater pump may be faulty, I am seriously contemplating getting a professional engineer involved now, I am completely fed up with the whole thing now. I hate having to do this, I like to rely on my own skills whenever I can, but this is clearly beyond me .

Did you chek the heat exchanger, elbow and all the other pointers I've given you? Sea trial under load is the answer with the heat gun, data is key to fault finding.

Is the engine actually boiling over, ie water being pushed past the filler cap? If not it cold be an electrical issue giving wrong readings.

 

[Mr Googler]

I would throw a few £'s at volvopaul for his skills. A few hours and he could well have the answers for you. Sun will be out soon and you don't want to miss it!!

 

[No Regrets]

I'm with Paul.

You have water being pumped through engine, thermostats OK, so it's either a blockage in the heat exchanger, or electrical issue.

I haven't yet seen a water pump fail in terms of actually pumping coolant terms yet (they usually leak first!) but must be possible.

Take a peek at the heat exchanger, might need cleaning out!?

 

[CaptainMike1970]

I've just had my KAD300s flushed with Rydlime (sp?), the boat was out of the water for various reasons at RK Marine and they have got his bag thing they put over the out drive, fill it with Rydlime and fresh water and then run up the engine, get it warmed up on water and Rydlime, then shut off the engine, let it fizz for a while, then run the engine again, flush all the cr4p out and then flush it all out again on fresh water.

Apparently the **** that came out had to be seen to be believed. Since being flushed the operating tempature going up/down the river, at normal cruise speed and at WOT are allnoticeably lower on the gauges.

I think that i was good preventative maintainence.

The issue I think is that most boat yards will to let you run the engines up on the hard.

I hope you find the problem.

Mike

 

[rafiki_]

I'm with VP on this. Likely to be the heat exchangers, but you need proper data to fully solve the problem.

 

[FalconSteve]

Hi all,

thanks for your suggestions and comments. As far as the heat exchanger hypothesis is concerned, I stripped it down after the initial problem occurred last year, it was quite badly blocked at the lower level (I think the level that the water sits when not flowing). Below are the pictures before and after I cleaned it through.

I didn't check it again today, to be frank I was really fed up as I thought the problem had been cured, my sea trial after the cooling system was cleaned showed the temperature had stabilized within operating limits of the manufacturer and the alarm no longer sounded. I have pm'ed vp and asked him to look at it for me, as some of you say, the expert examination may point to something that I'm missing. It is possible that there might be an electrical failure leading to inaccurate gauge reading, the engine certainly felt significantly hotter than the port engine. I'll let everyone know what Paul finds when he visits.

Thanks everyone.

 

[dpb]

I have just cured a similar problem that turned out to be the gauge or connections at the sender (not sure which as both done at the same time). The best thing I did initially was to buy an infra red hand held temp gauge with which I was able to confirm that both engines were infact at the same temp even though one gauge was way high, it even rose and fell with engine load!
Anyway, took gauge home, hair dryed it and left it open in the house for a week, and cleaned up and re crimped the terminals at the sender and now all readings are fine......

 

[Peanuts]

I have a couple where it has just been an airlock, removed the sea water lid, filled up with water, replaced lid and overheating problem sorted.

 

[Groot T]

Hi Steve,

This is just my 2-pence worth but it could be something to keep in mind.

Onboard Dads boat, we wanted to clean the raw-water system as we suspected there was some internal build up of calcium in the system. We could tell this because when we squeezed the flexible black rubber hose there was an audible crunch from inside it. Could very well be your system has build up in areas where you can't get to or see.

To clean out the entire system we used a product called rydlyme, http://www.rydlymemarine.co.uk/. We then got our hands on a whale gulper pump (any pump that can operate dry without burning out the motor will do), and jerry rigged a system which flushed through the engines system and used a big tub as a reservoir. I will see if I can dig out any photos of what we did.
It takes a while to do but it cleaned out all of the internals.

Be warned: Rydlyme will eat your anodes very quickly. So remove them from the blanking plugs first before you get this system on the go.
On the plus side, if you do have a broken anode in the system, the rydlyme will eat it all up.

Good luck buddy.

Toby

 

[volvopaul]

Hi all,

thanks for your suggestions and comments. As far as the heat exchanger hypothesis is concerned, I stripped it down after the initial problem occurred last year, it was quite badly blocked at the lower level (I think the level that the water sits when not flowing). Below are the pictures before and after I cleaned it through.

I didn't check it again today, to be frank I was really fed up as I thought the problem had been cured, my sea trial after the cooling system was cleaned showed the temperature had stabilized within operating limits of the manufacturer and the alarm no longer sounded. I have pm'ed vp and asked him to look at it for me, as some of you say, the expert examination may point to something that I'm missing. It is possible that there might be an electrical failure leading to inaccurate gauge reading, the engine certainly felt significantly hotter than the port engine. I'll let everyone know what Paul finds when he visits.

Thanks everyone.

Steve I've just caught up n this thread, those rubber seals don't look good mate, remember its. Two stage heat exchangers, the sea water just doesn't enter and flow, it goes back and forth twice but if it bypasses the rubber seals it goes nowhere but the easy way, out the exhaust!

 

[volvopaul]

How did you get on today after our chat Steve?

 

[FalconSteve]

Hi Paul,

Just got home now, I took the exhaust elbow off as we discussed, it wasn't completely scaled up, but it had substantial deposits in all the sections so I have cleaned the worst of the deposits out with a screwdriver and the flow looks good when I run the pontoon water hose pipe through it. I have put it back together and will conduct a seatrial on Thursday. I will also rev the engine hard prior to leaving the pontoon to ensure any airlocks are cleared. I think you were onto something when you told me about that one! It is a possible explanation for the radical overheating after the boat was lifted and re-launched. I will change those rubber seals while I've got the heat exchanger cover off, as you rightly say they are showing their age and the water could be bypassing the heat exchanger, it certainly won't hurt to put new ones in place.

For the benefit of others who may be interested, Paul kindly spent 20 minutes on the phone with me today, I described the actions I had taken when the boat was re-launched and because I only crept along between Shamrock Quay and Ocean Village at 1200-1500 rpm, there is a good chance that there was a positive water pressure from the exhaust end of the raw water system which was resisting the flow of raw water through the system, essentially the raw water was trapped in the engine and couldn't exit due to the back pressure. The cure to this is to rev the engine hard for about 30 seconds which will blow any air in the system out and neutralize the pressure through the raw water system. Once this is done the raw water should flow smoothly and do it's job properly. I didn't do this and it provides a compelling explanation of the boat not overheating on it's way from Ocean Village to Shamrock Quay 2 weeks ago, and suddenly developing the fault on it's return, as no elements of the cooling system were touched during it's time out of the water, the back pressure hypothesis seems highly plausible.

I'll feedback to the forum once I've sea trialled the boat (hopefully Thursday), the combination of cleaning the exhaust elbow and releasing the back pressure in the system may make a substantial difference and bring the operating temperature of the engine back within operating limits.

I'd like to sign off today with a big THANKS to Volvopaul for his time and trouble today, you really are a top man Paul and I will most certainly buy you a beer (or several) when we meet next. Paul has been a constant source of good advice to me with the many teething troubles I have had. Thanks to the others who have offered advice to me as well, the forum is a fantastic resource for amateur mechanics like me, you are a great bunch of fellas

Steve

 

[FalconSteve]

I have a couple where it has just been an airlock, removed the sea water lid, filled up with water, replaced lid and overheating problem sorted.

Hi Peanuts,

Your cure may be something similar to the advice I have received from Volvopaul today, I presume you were filling the water into the entire system so it would have same effect. Thanks for your help

 

[FalconSteve]

Hi Steve,

This is just my 2-pence worth but it could be something to keep in mind.

Onboard Dads boat, we wanted to clean the raw-water system as we suspected there was some internal build up of calcium in the system. We could tell this because when we squeezed the flexible black rubber hose there was an audible crunch from inside it. Could very well be your system has build up in areas where you can't get to or see.

To clean out the entire system we used a product called rydlyme, http://www.rydlymemarine.co.uk/. We then got our hands on a whale gulper pump (any pump that can operate dry without burning out the motor will do), and jerry rigged a system which flushed through the engines system and used a big tub as a reservoir. I will see if I can dig out any photos of what we did.
It takes a while to do but it cleaned out all of the internals.

Be warned: Rydlyme will eat your anodes very quickly. So remove them from the blanking plugs first before you get this system on the go.
On the plus side, if you do have a broken anode in the system, the rydlyme will eat it all up.

Good luck buddy.

Toby

Hi Toby,

I guess you saw the photos of the heat exchanger that I posted, I thought the whole system would be this bad, luckily the build up was restricted to the lower reaches of the heat exchanger in my system, the oil cooler, and the charge air cooler were both as clear as a bell, I had quite a shock when I saw the state of the exhaust elbow though, the rydlyme flush is something I'm interested in doing, if you have any photos of the rig you used I'd like to see how you did it

 

[FalconSteve]

I have just cured a similar problem that turned out to be the gauge or connections at the sender (not sure which as both done at the same time). The best thing I did initially was to buy an infra red hand held temp gauge with which I was able to confirm that both engines were infact at the same temp even though one gauge was way high, it even rose and fell with engine load!
Anyway, took gauge home, hair dryed it and left it open in the house for a week, and cleaned up and re crimped the terminals at the sender and now all readings are fine......

Hi dpd,

I switched my sensors around last year and they both seem to be working within the appropriate tolerances, many of the comments I got in my thread last year on the subject described the electrical problem of the gauges in one way or another. It goes to show that you can't always rely on the gauge readings doesn't it? I bought an infrared thermometer like you and for £15 it proved invaluable.

 

[FalconSteve]

is the exhaust staying cool?

if not its a raw water problem, if it is it's fresh.

if it's fresh, check thermostat and coolant pump. On mine the coolant pump was spinning on the shaft, but this was only noticeable on the bench with a bit of force behind it.

Hi Mark,

Good to hear from you, I like the simple logic, I am hoping that Volvopaul's suggestion might be right in my situation, it seems to fir the circumstances, of course things can (and often do) break on boats to coincide with seemingly innocuous events, if she still overheats after the sea trial on Thursday, I may be inclined to look at the fresh water pump. Hope things are going well with your new boat, have you finished all your upgrades?