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Old 17-11-2015, 05:48   #46
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Re: 2GM Yanmar Oil in Exhaust

but leaking oil while idling not ! think the rings arnt sealing or head gasket gone
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Old 17-11-2015, 05:52   #47
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Re: 2GM Yanmar Oil in Exhaust

I think the engine is just way over propped and that is the reason why I have run into trouble pushing the engine past 2500 rpm, stupid previous owner wanting to save fuel I bet !!
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Old 17-11-2015, 11:11   #48
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Re: 2GM Yanmar Oil in Exhaust

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thanks for the advice, it hope it is a blown head gasket and not the rings!
Sometimes with a blown head gasket you will hear the engine start on one cylinder and the second one will kick in a few seconds later. If it is a blown head gasket or if you remove the head at all it's a good idea to check or have it checked for flatness. A straightedge on edge and a feeler gauge can do that.

Another danger from being over propped and creating black smoke is the unburnt fuel washes the lube oil off the cylinders, leading to increased wear.

A compression test is the best thing to do first.

( and check your GPS menu /units /speed sometime. Often the initial, when new, default setting will be kilometres / hour instead of knots; especially in Aus / NZ where metrics are official. Knots will be an option in the "units" in the menu.
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Old 17-11-2015, 11:26   #49
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Re: 2GM Yanmar Oil in Exhaust

I should note that when I had bad rings on one cylinder in my yanmar, it did not smoke at all. It was $%^&* hard starting starting and drank oil like a drunken sailor through rum, at a quart every 12-16 hours. But I had no smoke at all.

If you had broken rings on a 2gm20, it would be extremely hard to start.

If the engine starts easy, the rings are good. A blown head gasket can also cause crankcase over pressure.
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Old 17-11-2015, 11:52   #50
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Re: 2GM Yanmar Oil in Exhaust

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I should note that when I had bad rings on one cylinder in my yanmar, it did not smoke at all. It was $%^&* hard starting starting and drank oil like a drunken sailor through rum, at a quart every 12-16 hours. But I had no smoke at all.

If you had broken rings on a 2gm20, it would be extremely hard to start.

If the engine starts easy, the rings are good. A blown head gasket can also cause crankcase over pressure.
Fill up the oil tank and give me a qt. of fuel.

I hope he finds a simple answer to the smoke and slick, and reprops. probably less pitch.

I could be wrong but a big shallow prop. for a displacement hull. Not by any mean suggesting a dia. increase do to sailing drag, just a reduced pitch, for him.
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Old 17-11-2015, 12:12   #51
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Re: 2GM Yanmar Oil in Exhaust

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but leaking oil while idling not ! think the rings arnt sealing or head gasket gone
Do a compression test with a proper diesel gauge. Remove the injectors and the gauge will replace them individually. One that I borrowed from a diesel workshop printed out the pressure on a special strip of paper. If you can borrow a gauge they will tell you how to use it. The Yanmar cylinders number from the flywheel;the rear of the engine forward. The one next to the gearbox is No.1. If you don't want to do that yourself get a diesel mechanic to do it.

It's the first and easiest step to do and is the beginning of eliminating the various possibilities.
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Old 17-11-2015, 15:28   #52
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Originally Posted by miabellabrian View Post
I think the engine is just way over propped and that is the reason why I have run into trouble pushing the engine past 2500 rpm, stupid previous owner wanting to save fuel I bet !!
A redundancy.
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Old 17-11-2015, 17:20   #53
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Re: 2GM Yanmar Oil in Exhaust

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I think the engine is just way over propped and that is the reason why I have run into trouble pushing the engine past 2500 rpm, stupid previous owner wanting to save fuel I bet !!
There is a normal recommendation for the 2GM which purely from memory I think is 15" X 10". That will depend to some degree on whether it's a fixed, or a folding, or a 3 blade prop, and on the size and weight of the boat.

With my 2GM 20 sail drive, I'm using a 16" Kiwi Feathering 3 blade prop which has an adjustable pitch, that can be pre set. They use degrees of pitch instead of inches.

On my 30' yacht if all the stars are in alignment with perfect conditions and empty water tanks etc I can just touch 7.2 knots at 3400 rpm. Normally I don't go much over 6 / 6.5 knots. I cruise around 3000 rpm. If I run against the mooring lines in the marina I can achieve 2700 rpm with black smoke, but I don't try that often and only for a second or two if I do.

A prop shop will be able to make a recommendation as they are doing that all the time. Some prop shops only deal with outboard motors so you need one that handles your type of boat and engine. Within limits an existing prop can be modified both in diameter and pitch by a prop shop. An experienced diver can do prop changes, though I prefer hauling out to do that.
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Old 17-11-2015, 18:49   #54
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Re: 2GM Yanmar Oil in Exhaust

I had lower rpms by 500 under max and bad blowby on one of my 2gm20, i replaced the exhaust hose,it was coming apart internally and made sure the loop was not too high and it fixed my problems,

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Old 17-11-2015, 20:39   #55
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Re: 2GM Yanmar Oil in Exhaust

Ok...I'm unsubscribing. This is a train wreck in slow motion...later guys.
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Old 17-11-2015, 21:21   #56
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Re: 2GM Yanmar Oil in Exhaust

Thanks for your contribution Celestialsailor.

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Old 17-11-2015, 22:54   #57
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Re: 2GM Yanmar Oil in Exhaust

Thinking of buying a compression tester from eBay, will they do the job or waist of money, I went to the yacht today and the engine started straight away, excessive smoke/air coming out of the oil filling cap when removed, and oil in the exhaust, no signs of water in the oil sump. Looks like I'm getting bubbles in the heat exchanger. I put some transmission fluid in the injector inlets in a desperate hope that that may loosen a non sealing ring ( I can dream right). So was thinking to get a compression tester and do the check without and with oil in the cylinder as was recommend to me to see if the pressure changes. Hopefully identifying ring issue or valve issue, right? Also checked the valves they seam like they have normal clearance. Just don't want to service the head and find out the bottom end needs rebuilding too, I do think that will be the case .

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Old 18-11-2015, 00:12   #58
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Re: 2GM Yanmar Oil in Exhaust

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Originally Posted by miabellabrian View Post
Thinking of buying a compression tester from eBay, will they do the job or waist of money, I went to the yacht today and the engine started straight away, excessive smoke/air coming out of the oil filling cap when removed, and oil in the exhaust, no signs of water in the oil sump. Looks like I'm getting bubbles in the heat exchanger. I put some transmission fluid in the injector inlets in a desperate hope that that may loosen a non sealing ring ( I can dream right). So was thinking to get a compression tester and do the check without and with oil in the cylinder as was recommend to me to see if the pressure changes. Hopefully identifying ring issue or valve issue, right? Also checked the valves they seam like they have normal clearance. Just don't want to service the head and find out the bottom end needs rebuilding too, I do think that will be the case .

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A compression tester for a car will be no good with a diesel engine. A diesel engine has more than 2X the compression ratio of a normal car. When I wanted to do a compression test on my Yanmar I borrowed a gauge from a diesel workshop. It looked very expensive; at a guess maybe $500. It replaces an injector and is retained by the injector mount. It printed out on a slip of paper.

The normal valve clearance is +8 thou"

You might need to get a diesel mechanic to do an assessment first rather than a fix.
I see you are at Lake Macquarie which as I remember from driving around might be remote from marine services. Is there a diesel truck service workshop nearby? That's Lake Macquarie NSW Aus I'm assuming.
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Old 18-11-2015, 03:08   #59
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Re: 2GM Yanmar Oil in Exhaust

If you want some independent professional Yanmar advice, get in touch with Minnards Diesel in Newcastle. These guys know Yanmars backwards and are always helpful with over the phone advice.
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Old 18-11-2015, 03:11   #60
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Re: 2GM Yanmar Oil in Exhaust

Two simple checks you can do regarding the blow by is pull off your mixing elbow and clean out any carbon build up and check the PCV valve.
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