R-25 Yanmar - temperature of exhaust elbow?

[captstu]

Hi, My boat's 4BY2 has been down with "overheat" for about 2 weeks - I was guessing it was a leaking heat exchanger because it lost about 1 quart of water in about 10 minutes with no water in the oil and no leaks I can find into the bilge.

I could not get the heat exchanger off - so I asked a local Yanmar shop for help.

The removed the exchanger, sent it out for cleaning and pressure testing and found no leak.

Now they want to remove the transmission oil cooler (it isn't overheating) and the air charge cooler - both are salt water cooled and both feel cool to the touch.

They feel the 1/2 missing blade on one vane I found when changing the 2 year old impeller was clogging a passage and impeding the flow of water. There is significant water flowing thru the sea chest and substantial water visible exiting the exhaust.

I was hoping to test the water temperature exiting the heat exchanger before it enters the elbow with an IR thermometer. It feels cool to the touch but I don't know how it "should" be.

QUESTION: What is the temperature of the water exiting the heat exchanger before it enters the exhaust mixing elbow?

Could someone with an IR thermometer please measure their engine's exhaust water and let me know?

thank you.

 

[knotflying]

Stu,

If you have an advanced type of multi-meter you have the ability of measuring temperature. Why not remove a clamp and slip the probe in and then re-clamp. then run the engine and get a reading. You may get slight leakage where the wire goes in, but it will be insignificant. However, I am not sure what measuring the exhaust water temperature will do for you. You already know that the engine is overheating and that would be related to the coolant temperature.The exhaust water temperature will be a matter of what the ambient water temperature is and how hot the coolant temperature is and the transfer of heat from one to the other. There are so many variable I am not sure you can do a comparison anyway.

Additionally, I think you have narrowed down the possibility of there being a leak. You are not getting additional level in your oil and it looks good so you seem to have ruled out a head leak. I am also assuming that your coolant isn't getting so hot that it is expanding into the recovery tank and overflowing, hence the loss of fluid. All indication are that there is a leak since you have to add coolant and the leak is not related to engine components. I can see this is frustrating, but keep looking.

 

[captstu]

The issue is I was forced to turn the boat over to a mechanic because I could not reach the necessary parts to remove the heat exchanger.

The Mechanic cut his way into the engine by cutting the hoses and cutting the belts and then planning to order new parts.

Now that mechanic is planning to cut out the air charge cooler and the hydraulic oil cooler for the reverse gear in the transmission because they believe that a vein from the raw water pump is causing the problems. This is nonsense.

When the problem began I removed and replaced the impeller on the raw water pump as part of the normal maintenance since the old one was two years old. The raw water impeller I removed Had one partially damaged vein with a small portion of that vein missing.

I remove the zincs and backwashed the heat exchanger and the raw water cooler to try to get out The Debris and remaining zincs.

I don’t know if anything came out.

Prior to calling the mechanic, I cleaned the top of the Seachest so I could see through it easily and observe significant water flow. I also observed significant water flow out of the exhaust pipe.

I’m looking for a way to convince the mechanic not to remove the raw water pump, hydraulic cooler, and the air exchange cooler because, being Yanmar, it may not be possible to easily get the hoses they will cut in the process.

I had hoped by showing them that the exhaust water coming out of the heat exchanger was at the expected lower temperature so they would be convinced that any veins stuck in a hydraulic cooler or the air exchange cooler was not significantly influencing the water flow that thus need not be removed.

Were into our third week on this overheating without finding the overall cause. I don’t see the work they’re planning to do next week as contributing to finding the cause of the water loss. Their Assumption is that the engine is overheating because of insufficient water flow through the heat exchanger.

I’m looking for a measure of the exhaust water temperature so I can prove to them that the heat exchanger is getting both adequate water and sufficiently cool water and water flow is not the problem.

If insufficient heat exchanger flow was causing a loss of a quart of water from boiler off, the volume of steam would be giagantic since I’m losing a quart of water in 10 minutes.

I’m facing a combination of problems, Both an overheating problem and a mechanic that does not seem to be able to fully diagnose the issue before randomly replacing parts he can not obtain through the whole wholesale supplier.

I’m looking at a replacement engine but I honestly don’t think this is going to solve the underlying problem since I am not capable of putting the engine in myself and I’ve not found a shop that I trust to do good work.

 

[NorthernFocus]

From what you've described I'd not let that guy touch my boat again. Doesn't sound like the sharpest knife in the drawer. I'd have been done with him when he cut the belt off. I can understand aged hoses having to be cut off but in all of my experience I've never run across even a shade tree mechanic that cut off belts.

When you say the engine is losing a quart of coolant in an hour is that at cruise RPM or at idle? Also does it only overheat at cruise?

 

[BB marine]

In troubleshooting overheat issues / coolant loss issues sometimes one leads to the other. You must isolate your repairs you have made to the system insteps. What started first overheat or coolant loss ? Did you change the impeller after an over heat and find the partial vane missing? I don't think that a partial vane missing will cause an over heat, but if this has happened a few times thru out the years or the trans/gear cooler was already partially plugged may be that is the problem of the over heat. Did you see any difference in temperature after exchanger was cleaned and pressure checked installed and sea tested ? ( I agree with NorthernFocus A mechanic that starts cutting hoses and belts needs to go). If not you at least took exchanger out of the equation. If there is any question of sea water coolant flow that is the direction you must go to resolve your over heat issue. This may have been the cause of the coolant loss issue a over heat causing damage to a cylinder head , gasket, manifold or as simple as a damaged o-ring in the closed cooling side of the cooling system. I would go from Point A ( thru hull ) sea strainer, hoses to sea pump, hoses out of sea pump trans cooler, air cooler , Exchanger (done) to Point F Exhaust elbow. remove ,inspect, clean, install, sea Trial, all components . Unfortunately the Ranger Tug engine placement does not make any of this easy , but with time ,effort , scratched up arms and a bunch of Aleve it can be done You need to resolve the over heat issue, that most likely was the source of the coolant loss issue. Good luck !

 

[captstu]

When you say the engine is losing a quart of coolant in an hour is that at cruise RPM or at idle? Also does it only overheat at cruise?[/quote]

To be fair, the Yanmar service man manual says to cut off the hoses and belts and replace them when the equipment involved requires service.

My concern is that it’s so difficult to get Yanmar parts that cutting the belts or houses before you have a replacement is something to be avoided.


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[captstu]

The engine appears to be losing about 1 quart of water in 5 to 10 minutes running at 3200 RPM. It appears you can run it for a longer time, several hours, if you stay at 2000 RPM or below.

I see no signs of: entering the bilge. I’ve sprinkled white powder under any areas that could be leaking and there’s no signs of any dripping.

I removed the cabin heater from the circuit.

I checked the connections to the domestic hot water heater carefully, they are not leaking.

I turned off the domestic water pump and open the faucet on the hot water and ran the engine at 3200 RPM and no water came out of the faucet. This makes me think the hot water heater is not leaking internally.

There really is no where else to turn for Yanmar service in this area. One authorized dealer stop servicing diesels altogether and the other one did some serious damage the engine about three years ago.

I don’t think the head gasket is leaking water. There is no signs of any irregularity in the engine running and no smoke coming out of the exhaust add any RPM.

I open the inspection valve on the exhaust manifold before the turbo charger and it was dry. While the water could’ve boiled out it leaked, The volume of steam would’ve been produced in exhaust would be gigantic.

I remain convinced that the heat exchanger is leaking internally only because I think everything else is been ruled out.

If the mechanic is able to get the engine running again and it still leaks, I have made up a pressure tester that would allow me to pump air into the heater line to see if the end it will hold pressure at a lower temperature. That is my current best guess.

Starting to look at Volvo D threes as a replacement but I don’t know where to have it installed as beyond my capability to do it because it’s so heavy.

 

[knotflying]

Did you put a call into Mastery? They are in St. Petersburg, FL. Two things, a) sometimes discussing the issue with them helps because they may have come across the issue before, b) ask them to recommend the best mechanic they know of and tow the boat there.

 

[captstu]

No, I did not call Mastry - good idea. Thank you.