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Old 03-07-2018, 11:00   #1
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Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Hi all!

I am starting to refit a Southern Cross 31. It has a Yanmar 2QM10 engine that it doesn't seem to run. I dont have the history of the engine, the seller told me he thought the issue was low compression. From what I see externally it has little bit of rust but not much. I am working on removing the engine. The question now is.... Should I rebuild or replace it? If I replace it, should I go for another diesel or should I convert to electric? Help! I dont know what to do!!

I was thinking about rebuild it but I a dont think I have the skills / knowledge to do it and if I have someone else do it then I am not sure if it will make financial sense... I am all doubts...
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Old 03-07-2018, 15:29   #2
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Before thinking about removing /rebuilding / replacing, I'd have a good diesel mechanic take a look at it and diagnose the actual problem(s).
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Old 03-07-2018, 23:05   #3
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

^^ what StuM said +1000. These engines are tough and hard to kill but of course, excessive lack of care can kill anything! The engine might only be sick, not dead.

If it does need serious work, then you got to balance what you want from your refit. If you are looking for a good / excellent refit and a faultless cruising engine to last another twenty plus years and have enough dollars, then re-engine with a Beta around 20 - 25 hp.

If you only want a small auxiliary power plant to move the boat in and out of harbours, marinas etc, consider electric.

If you want a good refit with a dependable solid engine, then overhaul / rebuild the existing 2QM20. Do it yourself but farm out any specialist work - injectors / injector pumps / machining head etc. Keeping the same engine simplifies many things like shaft, exhaust, instrumentation, controls, engine beds, mounts etc etc. In fact the time taken to redo all these items for a new engine is probably about the same as the time taken to rebuild the 2QM20. These are not hard engines to work on and there is a shipload of technical support available on CF to guide you though any bits that are confusing to you.

Sounds like a nice project!
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Old 04-07-2018, 16:08   #4
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Thank you guys!

I am already getting ready to pull the engine out of the boat because I want a reliable engine... So either I get a new one or I will rebuild my yanmar 2qm20.

I like the idea of doing it myself but farming out specialist work
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Old 04-07-2018, 16:47   #5
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Hum. I would really test it before pulling. The qm series was a tough but simple engine. Easy to rebuild, if you can find parts. A better made engine then the newer ones. Probably need to shop the rings and bearings at custom shops. doable.

A new engine is $10k ish. A rebuild should be less then $1800 ish. qm has sleeves, so easy to do. I did bearings and rings on my 3gm30 in 2013, in the cockpit, for $1200 including machining. 720 hours on it now.

http://www.cruisersforum.com/forums/...ar-107705.html
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Old 04-07-2018, 18:14   #6
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Quote:
Originally Posted by leveche420 View Post
Thank you guys!

I am already getting ready to pull the engine out of the boat because I want a reliable engine... So either I get a new one or I will rebuild my yanmar 2qm20.

I like the idea of doing it myself but farming out specialist work
I'm with the test before pulling crowd & what Wotname said. You can buy a compression tester for less than what it costs for a mechanic to come look. Lots of stuff on youtube to help you learn. Rebuilding helps you understand your engine, something that will prove very useful to you.
Yanmar parts are a lot cheaper in the USA if you are in Aus or NZ, buy from there if you can.
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Old 05-07-2018, 00:47   #7
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Pull the injectors out and put a couple of squerts of engine oil ineach cylinder, then replace the injectors and bleed them and see if it will go then, it might have been used to charge batteries without a decent load on it and have glazed cylinders. If it starts put some good springs on the moorings and run it in gear hard for an hour or two.

These are good solid little engines, very good quality and old enough to have been built in Japan. You would gain a lot by doing an overhaul yourself including learning a lot about your engine which will serve you well in future.
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Old 05-07-2018, 04:21   #8
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

You guys are amazing! Thank you all for your feedback!

I think you convinced me to try to rebuild the engine. I love the idea of being familiar with my engine, I am sure that will be very useful when I am sailing. I am determined to pull it out so I can bring it to my garage and also so that I can redo the engine room too.
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Old 05-07-2018, 04:35   #9
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Quote:
Originally Posted by leveche420 View Post
You guys are amazing! Thank you all for your feedback!

I think you convinced me to try to rebuild the engine. I love the idea of being familiar with my engine, I am sure that will be very useful when I am sailing. I am determined to pull it out so I can bring it to my garage and also so that I can redo the engine room too.
I sure you won't be sorry with this approach and there is absolutely no better way of getting the engine bay refurbished than by having the engine out. You will be happy with the result.
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Old 05-07-2018, 06:15   #10
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

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I sure you won't be sorry with this approach and there is absolutely no better way of getting the engine bay refurbished than by having the engine out. You will be happy with the result.
Thank you! I hope so! I want to do it right! I am a bit intimidated by this engine project but at the same time I am getting motivated when I hear that is doable.

One of the first things I am going to try to do is check the compression. I think I found a compression tester in the boat, so the previous owner may have already checked and that's why the brooker thought the compression was low

I am going to start researching where in the US I can get parts for this engine

What part would you recommend to change for a good solid rebuild? Would you help me start drafting a list of parts that I will have to replace?
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Old 05-07-2018, 06:36   #11
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Quote:
Originally Posted by leveche420 View Post
I am going to start researching where in the US I can get parts for this engine

What part would you recommend to change for a good solid rebuild? Would you help me start drafting a list of parts that I will have to replace?



Here's one source and list:

2QM20 Common Rebuild List Sailboat Supplies, Engine Parts and Boat Parts


And here's a a powerpoint presentation with lots of photos of someone doing a rebuild.



J/30 Rhapsody #348: Rhapsody J/30 #348 Yanmar 2GM Rebuild
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Old 05-07-2018, 07:48   #12
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Quote:
Originally Posted by StuM View Post
Here's one source and list:

2QM20 Common Rebuild List Sailboat Supplies, Engine Parts and Boat Parts


And here's a a powerpoint presentation with lots of photos of someone doing a rebuild.



J/30 Rhapsody #348: Rhapsody J/30 #348 Yanmar 2GM Rebuild

This is great! Thank you so much!!
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Old 05-07-2018, 09:59   #13
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

I have been researching a little bit on how others have rebuilt this type of engines and it seems that nobody mess with the gearbox/transmission.

Because I dont know the status of the transmission... Should I take it apart and see how it looks inside? Whats is it in there that could potentially have to be replaced? bearings? gaskets? gears?
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Old 05-07-2018, 15:27   #14
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Quote:
Originally Posted by leveche420 View Post
I have been researching a little bit on how others have rebuilt this type of engines and it seems that nobody mess with the gearbox/transmission.

Because I dont know the status of the transmission... Should I take it apart and see how it looks inside? Whats is it in there that could potentially have to be replaced? bearings? gaskets? gears?
That is because the gearbox is torpedo proof (the engine is only bullet proof )!
Seriously, it is simple design with constant mesh gears, generously size bearings, well lubricated; there is not much to wear and very little to go wrong. The wet clutch plate is double sided and is the only thing to wear. It can be measured once you get the gearbox / engine split.

This is my Yanmar Y series gearbox (8 hp) and the Q series is very similar. You can see there isn't much in there.
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Old 06-07-2018, 10:28   #15
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

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That is because the gearbox is torpedo proof (the engine is only bullet proof )!
Seriously, it is simple design with constant mesh gears, generously size bearings, well lubricated; there is not much to wear and very little to go wrong. The wet clutch plate is double sided and is the only thing to wear. It can be measured once you get the gearbox / engine split.

This is my Yanmar Y series gearbox (8 hp) and the Q series is very similar. You can see there isn't much in there.
Thank you! So far I have received a quote for rebuilding the entire gearbox/transmission for $2,200. That includes replacing all hardware. I have another quote for disassemble, clean, inspect , reseal and test for $650. Right now do it myself sounds a little bit dangerous but having a shop do it seems a lot of money
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