Rebuild 2GM vs repower with 2YM15 or 2YM20 - Page 2 - SailNet Community

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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #11  
Old 02-28-2008
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I'm dying to hear how the water jacket looks, as I have a 28 year old Yanmar and face the same issues.
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Old 02-29-2008
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overheat issue

The fact your motor overheated a couple times and now there is smoke suggest a bad injector. If an engine has had a significant overheat you must first re-torque all head screws and re-calibrate your valves. The injector(s) usually have to be replace as well. If the engine has otherwise been well maintained it could be fine. Remember most the engine upgrades in recent years are for emission issues not design improvements
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Old 02-29-2008
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OM - Thanks for the input! When it did "overheat" once, I shut the engine down immediately. The 2nd time, I went below, pulled the hose off the exhaust elbow (I had left the clamp a bit loose), and the raw water started flowing / cooling in a few seconds. I don't think it would have overheated enough to hurt anything. I ran it for many hours after that, with no issues, other than using a bit too much oil / smoking only at high revs!
The engine always started immediately, even in the colder fall weather.
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Old 03-02-2008
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Rockter will become famous soon enough
If you suspect you are coolant-starved, try to let the motor cool before re-establishing the coolant. You risk a cracked block if you do not.

An engine that starts first time in the coldest of weather is really not going to have much wrong with it and there cannot be much wear in the bores or valves. If it's raw water cooled, the motor block and head will be cast iron and it really is fairly tolerant of being overcooked. This is not a quick-warp aluminium motor.

Be wary of messing with a sound motor to try to make it perfect. If it starts fine, and pulls fine and does not use too much oil, you really do not have much of a problem.

A new motor may not be so friendly.

I would leave it alone unless there is a formal problem.
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Old 03-02-2008
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In the older Yanmar GM models (raw water cooled) the hight temp. alarm will sound when the temp. reaches (if memory serves correctly) around 140, This is to prevent water evaporation leaving salt deposits clogging the water ways. Its been said that there were only two engines designed specifically for the marine environment the Atomic four and the Yanmar GM. I would also suspect if a proper water strainer has been in place your raw water galleys are fine.
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Billang - I had often wondered if the high temp alarm, on raw water engines, was set lower (as they have lower thermostats). Or, if they were set the same as the fresh water engines (probably around 180 - 190 degrees).
It does make sense to have a lower alarm value as well - why wait until it hits 180 or so, to sound an alarm - when, with a 140 degree thermostat, anything over 145-150 means something is wrong!

Thanks for the info.

Rocter - we have had similar discussions before, and I am always torn between the - if it ain't broke, don't fix - and the notion that we can have a look inside now, while it is out of the boat, and replace a few normal wear items, rather than put it back in without knowing. I know you are of the former view, and I repsect your opinions!! It seems people are baout 50 / 50 on whether to take off the head, clean / gring the valves, seats, etc, and see how everything looks. (that's based on some input from a Seafarer specific site as well).
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Rockter - Forgot to mention - Good tip on the letting the block cool, before getting the water going again - I guess I overlooked that, in my hunt to troubleshoot the problem, while it was running. I wanted to see at what hose / part, the water flow had stopped. As Billangiep states, if my engine does have a lower valued high temp alarm (around 140), then re-establishing the water flow, when it "overheats" to 140 or so, should not risk a cracked block, the way it would if the a alarm went off at 180, or so.

The engine did start well, and pull reasonably well (I think the boat is a bit underpowered anyway - when motoring into a 5-8' chop last year, in 25 kt + eadwinds, we could only motor a a couple of kts, where we would normally do 5 kts).

It did go through a quart of oil in approx 20 hours, on one trip. Didn't seem to burn as much the rest of the time.
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Northeaster, I would recommend that if your going through the top end go through the bottom as well. Doing work on the top end will surly increase compression. Those crank bearings have just as many hrs. as the valve seats ext.
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2YM15 (14hp) - (2YM20 - 21hp) - 3YM20 (29hp)

Quote:
Originally Posted by Northeaster View Post
(...)
In my case, if I change to the newer 2YM15,
(...)
But, if I am going to repower, It may be worth the extra $1100 engine cost, as well as a new / used prop / shaft, to get the added HP of the new 3YM20.
Dear Northeaster,

I am in the process of finding out which engine would be best for my Halcyon Clipper 27 (*)

You write having changed engine to a Yanmar 2YM15.
You also write considering a 3YM20.

It appears to me there are in this discussion 3 (Yanmar) engines in the running:

2YM15 (14pk) ŕ EUR 6060,-
3YM20 (21pk) ŕ EUR 6950,-
3YM30 (29pk) ŕ EUR 7990,-
(Prices incl. sales tax; April 2009)

My question:
What are the dimentions of your ship Northeaster?

The original engine of my boat was a Sabb 8hp. The max HP suited to the boat has been figured out as being about 12HP. A logical conclusion would thus be that the 2YM15 is the best match, at least mathematically. I like to make my boat ready for any waters: ocean as well as long trips upstream rivers. Having this in mind: will the 2hp over-powered engine be 'enough' to avoid to run the engine at all time at full power/noice? Maybe the overpowered 3YM20 never will be able to deliver its full potential but grant benefits one will have to miss with a 'right seize engine'?

Thank you for contributing to this forum. I would be most grateful if you could share your views regarding this subject with us.

Kind regards,
Nomadman


(*) My boat type: Halcyon Clipper 27
LOA: 8.23m (27'0")
Displacement: 3048kg (6800 lbs)
Original engine: SABB 8hp

Last edited by nomadman; 04-03-2009 at 09:32 PM.
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