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post #11 of 18 Old 04-18-2012
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Re: Rebuilding Yanmar 3GM30F; need advise $?

I had mine done at 26 years and it cost just about $5,000. This was a few years ago. The 3GM30 raw water cooled has been a solid tool for our boat. The Lancer 36 was built in 1981, I am assuming the 3GM30 was also built then. The rebuild took some time, 6 weeks but there was some welding needed. Any way glad I did it, it runs like new. I am very pleased.
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post #12 of 18 Old 04-19-2012
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Re: Rebuilding Yanmar 3GM30F; need advise $?

The previous and original owner of my C&C 32 removed the old Atomic bomb that the boat came with and replaced it with a brand new 3GM30F with a new 2.21/1 gearbox, shaft, and o-ringed stuffing box, cost $12,000. It has 500 hours on it and I still concider it not completely broken in.
At work, we run Yanmar engines on soil screeners, rockcrushers and many other pieces of earth moving equipment. These engines run in some of the worst conditions with minimal maintenance. Most engines will reach 10-12,000 hours before any major work is required, some will last even longer.
An engine with 3500 hrs. on it is just nicely broken in. You may want to look at external components like alternators water pumps, injectors, etc., but unless you are experiencing a problem the engine itself should be fine.
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post #13 of 18 Old 04-19-2012
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Re: Rebuilding Yanmar 3GM30F; need advise $?

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Originally Posted by SecondWindNC View Post
I think you may be jumping the gun with completely rebuilding a running Yanmar at 3,300 hours. The life expectancy of a well-maintained marine diesel can be well upwards of 5,000 hours (sometimes more like 8k-10k). Have you had problems with the engine that have led you to this?

I would suggest doing an engine survey instead. Have the compression tested, injectors tested, etc. Fluid (oil and coolant) samples can also reveal a lot about the engine. I'm sure there are some mechanics in your area that do engine surveys. Address any problems that the survey identifies, and go on enjoying your boat.

The Life Expectancy of the Marine Engine - BoatSafe.com
I agree with the above. Check the fuel injection pump. Most likely there is nothing wrong with it, but water in the fuel can cause premature wear. I would also replace the injectors or at least have them reconditioned as a poor spray pattern can cause premature cylinder wear. At the very least have the injectors tested. Of course have all pump impellers replaced. I would also do seals on any water pumps. If there is engine oil in the bilge, check front and rear crankshaft seals. Maybe oil is from poor technique with oil changes is the cause. Crankshaft seal replacement requires pulling the engine. . If this were direct cooled, no heat exchanger, I would disassemble and test for cracks and corrosion. If there is a heat exchanger, have that cleaned out of corrosion products and scale. If compression is not all right, pull the head. Maybe all you need is a valve job. The cylinder walls can also be measured and inspected for wear with the head off. If you have bearing material in the oil, pull the engine. You will probably need to have the crankshaft ground and certainly new bearings including camshaft, mains, and rods. You may be able to use the old pistons with new rings with cylinder glaze broken or honed. Diesel cylinders usually wear little because the diesel is light oil and does a good job of protecting the cylinders. If the engine has had seawater flood back into the cylinders because of excess cranking or poor cooling system design, a compression check should tell the story. Also check the cutless bearing on the propeller shaft for wear. Take the flange loose from the transmission, put a very short bolt between the flange on the transmission and the propeller shaft on the other flange, put the bolts back on and tighten to push the propeller shaft out of the flange attached to the propeller shaft. Do not use a slide hammer as this can damage the transmisison. Slide the propeller shaft out to see if there is any pit corrosion on the shaft. Stainless 316 and 304 steel is a poor choice for a propeller shaft. Consider 22 alloy: Western Branch Metals: Marine Propeller Shafting Also send the propeller out to have a computer analysis done to check for damage and get the shape and balance accurate.

Last edited by LakeSuperiorGeezer; 04-19-2012 at 12:01 PM.
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post #14 of 18 Old 04-19-2012
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Re: Rebuilding Yanmar 3GM30F; need advise $?

enjoying this thread.

I will be doing the same thing with my Yanmar 4JH2E. Only 1,000 hours, but sat idle for 10 years and overheated pretty bad by running without water flow for about 20 minutes.

It took me around FL (through the Okeechobee Waterway) without any real problems. The problems were easy to identify: bad mounts, hoses need replacements, very dirty fuel tank; but nothing serious. No smoke or anything out of the exhaust.

My biggest worry is what may have happened when it ran hot. The engine is currently pulled, so I'm unsure how I would get it tested.

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post #15 of 18 Old 04-19-2012
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Re: Rebuilding Yanmar 3GM30F; need advise $?

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Originally Posted by Beersmith View Post
enjoying this thread.

I will be doing the same thing with my Yanmar 4JH2E. Only 1,000 hours, but sat idle for 10 years and overheated pretty bad by running without water flow for about 20 minutes.

It took me around FL (through the Okeechobee Waterway) without any real problems. The problems were easy to identify: bad mounts, hoses need replacements, very dirty fuel tank; but nothing serious. No smoke or anything out of the exhaust.

My biggest worry is what may have happened when it ran hot. The engine is currently pulled, so I'm unsure how I would get it tested.
If there was coolant in the engine after the 20 minutes even if it was boiling, then almost certain there was no damage. Was there any coolant after you let the engine get cold?

If the coolant was gone, and the head is made of aluminum, there will almost always be cracks. A machine shop that specializes in welding of engine heads should have a look at it. Test the head for cracks. Almost always these cracks can be repaired, but the welder has to know what he is doing.

Cast iron can take a lot of abuse. Probably no cracks if coolant was boiled out of it, but need to check the head for cracks. Harder to weld and sometimes a new head is needed, cannot be repaired. Was the paint burned off the head?

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post #16 of 18 Old 04-20-2012
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Re: Rebuilding Yanmar 3GM30F; need advise $?

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If there was coolant in the engine after the 20 minutes even if it was boiling, then almost certain there was no damage. Was there any coolant after you let the engine get cold?

If the coolant was gone, and the head is made of aluminum, there will almost always be cracks. A machine shop that specializes in welding of engine heads should have a look at it. Test the head for cracks. Almost always these cracks can be repaired, but the welder has to know what he is doing.

Cast iron can take a lot of abuse. Probably no cracks if coolant was boiled out of it, but need to check the head for cracks. Harder to weld and sometimes a new head is needed, cannot be repaired. Was the paint burned off the head?
it is aluminium, but there was coolant left after the whole ordeal. I remain hopeful that the head is crack-free, but will get it checked out.

My boat rebuild/sailing blog:
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post #17 of 18 Old 04-20-2012
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Re: Rebuilding Yanmar 3GM30F; need advise $?

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Everyone here was right on the mark. My mechanic called me this morning and stated that the Yanmars are merely bullet proof and unless it starts hard and you see smoke at cruising rpm(s), no overhaul should be done. If maintain, you can put 5000 hrs on them.

It was recommended that we pull the engine this winter which I have agreed to. Going to replace the engine mounts (collapses), replace the water pump, belt, complete tune up, adjust the valves, replace the alternator and starter, wash engine and repaint, etc... basically going through the engine from top to bottom. This will also give me a good base line for maintenance and give me a chance to replace the hoses in the engine compartment (as needed), go through the shaft and drive train, secure the loose wiring, and clean up / paint the engine compartment.

By the way, two budgets received to date completely overhaul the Yanmar engine was $6,000 to $9,000. (ouch!!!) Everything I am talking about above will costs $2,000 to $2,800.
Clean up (maybe even paint) and keep the old parts on the boat for emergency spares if they still work. Spray with rust preventitive and seal in a plastic bad.
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post #18 of 18 Old 09-22-2012
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Re: Rebuilding Yanmar 3GM30F; need advise $?

Sorry for butting in but...
I just started a 3 GM 30 F and it ran fine with good oil pressure. ( only ran it for perhaps 2 or 3 minutes )
I shut it down and set up water to the system as she is setting on the hard.
When I started her this time I had very low oil pressure. ( I checked before I started and oil looked good and was close to full )
Can anyone give me some advice on this.
I have rebuilt engines in the past so expect if I must that is how I will go.
Thanks to any who reply.
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