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Old 08-06-2018, 14:21   #1
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Troubleshooting Yanmar 2GM

Hi,
My father and I own a 32" Beneteau with a Yanmar 2GM inboard. The engine is currently dead, and I would like to get some advice on the best route to troubleshoot the current issues. We are having the boat pulled out to be painted in a week, so I am trying to figure out what to do before then.

A few years ago a friend borrowed the boat, and wrapped a line around the prop which cracked the propeller shaft. That was repaired, however I don't know if it could have caused other longterm issues.

A few months ago we determined that the salt water cooling system was getting clogged, and attempted to clean it with no success. At the next startup which only lasted a few minutes, the engine was expelling oil from the exhaust, it drained a significant amount of oil below the engine, and there was water in the oil when viewed from the dipstick.

My dad thinks the engine is a total loss, but I am trying to figure out the best way to establish if that is the case, or if it can be repaired. Are the symptoms above indicative of any known issues? What steps should we ask a mechanic to take to determine the cause, or if the engine is a candidate to be rebuilt? It only has about 2000 hours on it, but has done a lot of sitting since it was built in 1986.

Thank you in advance!
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Old 11-06-2018, 14:16   #2
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Re: Troubleshooting Yanmar 2GM

At the very least your head gasket is blown. You need to do a compression check to confirm. If you're pumping oil out with the exhaust water that indicates bad piston rings and valve seals. Time to tear it down and rebuild it. I've got one in the shop that I'm breaking down.
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Old 11-06-2018, 14:41   #3
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Re: Troubleshooting Yanmar 2GM

Sounds like a cracked block from freezing. Are the freeze plugs blown out?
Did it overheat when you determined it wasn't getting raw water flow?
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Old 11-06-2018, 15:16   #4
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Re: Troubleshooting Yanmar 2GM

I don't think anything has frozen, the boat is in Southern California. I am going to have a mechanic take a look at it next week, but I am trying to get a handle on things before then.

We ran salt away through the engine because it had been overheating previously. When we did this the salt away did not come back out, which is why I am not sure it worked. After this it ran well for about 20 minutes, no overheating, before we noticed the oil leaks and shut the engine off.

Besides a compression test, should I do anything else to determine if the engine can be rebuilt, or if it needs to be replaced?
What is a fair ballpark estimate to have the engine rebuilt?
Is it possible to retrofit freshwater cooling?

Thank you for the replies/advice/help!
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Old 11-06-2018, 18:10   #5
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Re: Troubleshooting Yanmar 2GM

Quote:
Originally Posted by Beneteau32 View Post
I don't think anything has frozen, the boat is in Southern California. I am going to have a mechanic take a look at it next week, but I am trying to get a handle on things before then.

We ran salt away through the engine because it had been overheating previously. When we did this the salt away did not come back out, which is why I am not sure it worked. After this it ran well for about 20 minutes, no overheating, before we noticed the oil leaks and shut the engine off.

Besides a compression test, should I do anything else to determine if the engine can be rebuilt, or if it needs to be replaced?
What is a fair ballpark estimate to have the engine rebuilt?
Is it possible to retrofit freshwater cooling?

Thank you for the replies/advice/help!
Several points:

Regarding the oil in the water and water in the crankcase, it is most likely sea water has entered the engine probably due to a failed exhaust elbow allowing water back though an exhaust valve into the cylinder. Also much sitting without starting is hard on the rings and cylinder. The bore gets a light coating of rust and this is removed at the next start thus increasing wear.

Regarding your flushing, unless you used a custom made fitting to replace the thermostat housing OR removed the thermostat and blocked the short hose from the block to thermostat housing before flushing, your flushing solution probably went out the exhaust. The correct way is to remove thermostat, block the hose mentioned above, remove the engine zincs (I think the 2GM has two, the 2GM20 does), remove the raw water discharge hose at the exhaust elbow and the raw water inlet hose after the water pump. Then circulate the flushing solution thought the block and head using an external pump (like a small bilge pump in a 2 gallon bucket). Depending on what flushing solution you use, this could be anywhere form 30 minutes to 24 hours. I can provide more detail if you wish.

Regarding converting the engine to using coolant and an heat exchanger; this possible but more difficult then many think. If you use Yanmar parts and if they are still available, it will be very costly. If you try it using after market components, there are several hard to solve issues - the thermostat aspects are not convertible and you have to fit a another water pump. However, it is unlikely you have any serious issues with the raw water cooling even though it may look seriously compromised. These engines are designed for a long life using raw water cooling. I have had 5 raw water cooled engines (3 Yanmars, 1 Buhk and 1 Arona). I am currently rebuilding a 1976 Yanmar and after a good descaling using Muriatic acid, the internal water jacket and galleries are almost as good as new. If you keep replacing the engine zincs and carry out a good flush (vinegar is as good as any) say every 5 years or so, the lifetime of the cooling aspects is almost indefinite. The main downside of raw water cooling is that the engine is designed to run cooler (to prevent salt precipitation) and thus is more inefficient. IMO, this is a small price to pay for a KISS cooling system.

The principle reason larger engines were initially coolant cooled was that they were never designed for raw water, they were auto or industrial engines by design. Now of course, the efficiency aspects prevents raw water cooling for new engine designs.

I think you will find your 2GM is rebuildable and IIRC, they used wet sleeves so at the worst, you will new new sleeves, pistons, rings, valves, and bearings.

It can be DIY job and there is no end of support on CF if you are unsure of your ability to do the work. Really you just need a suitable venue to carry out the work - garage, shed, basement etc.
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Old 11-06-2018, 18:34   #6
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Re: Troubleshooting Yanmar 2GM

Thank you for the detailed reply. I spoke with the boat yard again, and we decided the best game plan was to have them run some tests on the engine when they get the boat next week, then if they can't immediate point to something, like the head gasket, they are going to remove the engine and disassemble it to diagnose what the exact issue is. Once that is done, I will get quotes to repair it. I would do it myself, but I don't have the time or space right now.

With the replies here, and from what I have read elsewhere I am pretty confident it will be able to rebuilt, as far as I can tell nothing is cracked. Thanks again!
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Old 11-06-2018, 19:00   #7
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Re: Troubleshooting Yanmar 2GM

Quote:
Originally Posted by Beneteau32 View Post
Thank you for the detailed reply. I spoke with the boat yard again, and we decided the best game plan was to have them run some tests on the engine when they get the boat next week, then if they can't immediate point to something, like the head gasket, they are going to remove the engine and disassemble it to diagnose what the exact issue is. Once that is done, I will get quotes to repair it. I would do it myself, but I don't have the time or space right now.

With the replies here, and from what I have read elsewhere I am pretty confident it will be able to rebuilt, as far as I can tell nothing is cracked. Thanks again!
Sounds like a good plain
If you end up with a rebuilt engine, please check / replace the engine zincs every 1 or 2 years and carry out a vinegar flush as described above every say 5 years and the cooling aspects of the engine will last a very very long time.
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