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Old 18-11-2015, 03:15   #61
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Re: 2GM Yanmar Oil in Exhaust

Miabellabrian, can you confirm for us if your engine is a 2GM or a 2GM20 and if possible, year of manufacture?

Once you get the problem solved, it would be great if you let us know the final outcome!
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Old 18-11-2015, 04:45   #62
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Re: 2GM Yanmar Oil in Exhaust

Quote:
Originally Posted by miabellabrian View Post
Ok, lets look at the facts again. Firstly I said I thought the boat was over propped from the beginning, and as I have come to learn this can be proven by the fact that it revs higher in reverse than in forward.(lower gearing in reverse).....?
Whoever gave you the above gem of knowledge has got it completely wrong - sorry to be blunt

You may well be overpropped but this is not the way to confirm it. Many boats rev faster in reverse even if correctly propped.

A quick and dirty test is to motor in flat calm conditions at WOT with a clean prop, a clean hull and a good engine. With the right sized prop, you should get very close to max rpm as specified by the engine manufacturer. Unfortunately you can't do this right now as you don't have a good engine .

The proper way to compare your actual prop to that as specified by the prop manufacturer for your hull type and engine model.

Please note, this has nothing to do with hull speed, you will probably reach hull speed well before max rpm.

Here are some numbers that demostrate the above. My boat IS correctly propped and I have a 12 yearvold 2GM20 in as new condition.
With clean clean prop and clean bottom in flat calm conditions, I reach hull speed around 2700.
At WOT, I just make 3600 with no smoke.
With slight (normal) bottom fouling, I get 3400 with light black smoke.

Tied to the jetty and with a clean prop, I get 3200 at WOT and noticeable black smoke and a slight sludge on the water. With a slightly fouled prop, I just make 3000 with considerable black smoke and carbon/diesel sludge on the water.

You should get similar numbers if you have a 2GM20 except you will reach hull speed sooner. At a guess, maybe 2200 to 2400. If you have a 2GM, I THINK you could reduce all the above rpms by about 300 or so.
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Old 18-11-2015, 04:55   #63
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Re: 2GM Yanmar Oil in Exhaust

Actually was just looking at YouTube before looking at pcv valves, will check tomorrow, I recall seeing the outlet on the valve cover, but don't recall seeing the air inlet,guess I can find it in the manual.

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Old 18-11-2015, 05:44   #64
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Re: 2GM Yanmar Oil in Exhaust

You said you've got bubbles in the heat exchanger????

If so it's easy, pop the head off, check it for trueness, and pop a new head gasket on. Done........and change your prop.


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Old 18-11-2015, 15:50   #65
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Re: 2GM Yanmar Oil in Exhaust

Can blown head gasket cause oil in exhaust , no oil in heat exchanger, no water in sump oil ? Guess it depend on where the gasket has broken ?

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Old 18-11-2015, 16:52   #66
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Re: 2GM Yanmar Oil in Exhaust

There is one other place where fuel and oil can mix and this is in your injector pump. When the seals go bad oil will get into the fuel.

Have you actually ruled out an oil overfill?
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Old 18-11-2015, 17:02   #67
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Re: 2GM Yanmar Oil in Exhaust

I am not an expert at diesel mechanics by any stretch of the imagination. I do have an opinion though. (OMG a sailor with an opinion) You seem to be having problems with the engine. SailorChic (full disclosure she is my idol having torn apart one of these engines and then painting it purple and pink) has given you some goood advice. A compression test will give you a reading of the compression but a more precise check would be a leak down test. It could be difficult to find the proper fitting for your engine. I had to mill my own for a small kubota engine on my generator out of an apropriate sized bolt. The advantage of a leak down test is that it will accurately tell you where any problem exists. Valves, head gasket, rings. I suggest you do this prior to pulling the engine apart. I know you are in OZ but here in the sates you can buy them from Harbor Freight for a reasonable price. The adapters are sometimes more difficult to find. I have linked a video that shows how to do one.
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Old 18-11-2015, 17:08   #68
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Re: 2GM Yanmar Oil in Exhaust

All the Kanzaki transmissions on GM series engines have a greater reduction ratio on reverse, that's why it will rev out more.
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Old 18-11-2015, 18:01   #69
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Re: 2GM Yanmar Oil in Exhaust

OK If the OP has bubbles in the tank then he does not need a compression tester. Bubbles in the fresh water tank is a sure sign of a blown head gasket. You can get oil in the exhaust from the blown head gasket too.

That the engine started quickly says the rings are fine.

So take the head off, have it checked for flatness and shaved, only if necessary. Buy a new head gasket, new hoses and a new exhaust manifold gasket. and it's a easy 1/2 day fix. Remember to loosen the head bolts from the center out a 1/4 turn at a time.

Also a good time to buy new heat exchanger gaskets and clean the heat exchanger while the head is off. A 22 caliber brass brush is the perfect size to rod the tubes with.
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Old 18-11-2015, 23:37   #70
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Re: 2GM Yanmar Oil in Exhaust

Quote:
Originally Posted by lockie View Post
All the Kanzaki transmissions on GM series engines have a greater reduction ratio on reverse, that's why it will rev out more.
Sometimes people want a lower reduction than standard and put a reverse pitch prop on and run in reverse gear, with the controls switched around. I'm not suggesting that in this case as that would require a new prop.
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Old 19-11-2015, 00:04   #71
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Re: 2GM Yanmar Oil in Exhaust

Quote:
Originally Posted by sailorchic34 View Post
OK If the OP has bubbles in the tank then he does not need a compression tester. Bubbles in the fresh water tank is a sure sign of a blown head gasket. You can get oil in the exhaust from the blown head gasket too.

That the engine started quickly says the rings are fine.

So take the head off, have it checked for flatness and shaved, only if necessary. Buy a new head gasket, new hoses and a new exhaust manifold gasket. and it's a easy 1/2 day fix. Remember to loosen the head bolts from the center out a 1/4 turn at a time.

Also a good time to buy new heat exchanger gaskets and clean the heat exchanger while the head is off. A 22 caliber brass brush is the perfect size to rod the tubes with.
Good info. I'm not wishing to contradict you but the head nuts or bolts should be loosened in the reverse order from tightening. That is loosen the outside nuts first and the loosen center nuts last.

When tightening you start at the center and work outwards diagonally. You need a torque wrench to correctly tighten the head. You can get them from Repco or Supercheap Autos for $70 / $100. If you buy one make sure it covers the range of torque necessary. You can google that for your motor.
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Old 19-11-2015, 01:45   #72
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Re: 2GM Yanmar Oil in Exhaust

2GM20 head nut torques are 10 Kg-M (72.3 ft-lbs) for the 6 main (big) ones and 2.5 Kg-M (18 ft-lbs) for the 2 sub (little) ones.

I don't have the numbers for the 2GM but in a pinch, I would use the above .

It would be nice if the OP could clarify which engine he has!
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Old 19-11-2015, 03:09   #73
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Re: 2GM Yanmar Oil in Exhaust

Got a 2 gm, and yes the engine is probably 30 years old not sure, my guess of 12 yrs was way out, I was told by the mechanic who came to inspect the engine today. He seams to think it may just be worn out ( rings) but until a compression test is done dry and wet there is no way of telling for sure. Im getting a compression gauge from eBay, it the rings are the issue then I feel sorry for my yacht, became it will get some " stop smoke" of some sort, I'm not spending 5k or something like that getting the engine rebuilt, or perhaps find a used engine ?? Funny thing today is that the engine started first click today after soaking tranny fluid into each cylinder overnight. My conclusion so far is that when I removed the Transmission fluid today and went to start it some of the Transmission fluid left in the cylinder may have created a better seal around the rings and therefore made it easy to start today! ( still getting blow by, and oil in the exhaust water of cause)

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Old 19-11-2015, 03:10   #74
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Re: 2GM Yanmar Oil in Exhaust

2gm with a heatexchanger fitted by someone who owned the boat before

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Old 19-11-2015, 03:12   #75
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Re: 2GM Yanmar Oil in Exhaust

The mechanic said it wasn't bubles in the heat exchanger, just the rushing around of the coolant. Sorry

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