# Rebuild 2GM vs repower with 2YM15 or 2YM20



## Northeaster (Jan 13, 2007)

Hi Folks,

My mechanic brother is about to check out my 25 year-old (raw water cooled) Yanmar 2GM. The engine was smoking a bit at high RPMs / High load, but otherwise worked well. I did have an issue where the raw water flow stopped a couple of times, but when I pulled off the water hose on the exhaust elbow, there was a poof of dry air, then the water flow came back right a way, and worked fine after that. May be an intermittent failing water pump??

Anyway, he will do a compression test, possibly an oil analysis, and check the head (valves, valve seats, etc.) If all check out OK, He will replace gaskets, and I may still spend about $500-1000 for new engine mounts, and a rebuild (or gasket kit) on a 25 year old engine - that has been raw water cooled, in salt water, for 25 years.

I don't have extra cash!! But, I can get a new 2YM15 for $5800 + tax. or a new 3YM20 for $6900.

Any advice would be appreciated! If my engine does not test well (compression, oil analysis, or look at water jacket, etc), do you think it would be wise to replace with an engine of approx same HP (2 YM15), or, as they say most boats are underpowered, and we have strong tides in the area (35 ft tides, on the Bay of Fundy) - Should I consider the 21 HP (3YM20).
I assume that I would have to look at re-propping, or at least re-pitching, if I went with more power. I have an old fixed 3 blade prop, on my current 13HP (2GM)
The boat is a 1978 Seafarer 30 (book disp 8600lbs, crane said it weighed 10,000, with gear onboard)
- A new 3YM20 is only 38lbs heavier than a new 2YM15!
- I do plan on keeping the boat for the next few years, at least.
- My water heater would be much more efficient with a fresh water cooled engine


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## PBzeer (Nov 11, 2002)

Shaft length might also be an issue with a new engine. I would think if the boat isn't in your long term plans, I would think rebuild first.


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## JohnRPollard (Mar 26, 2007)

Will your brother be pulling the engine to do this work? Or doing it in place?

If he's taking it out regardless, and you plan to keep the boat for more than a few years, I would swap it for a new engine if you can afford it. 

That's a good price on the Yanmar 3YM20. But definitely compare it to the Betamarine BD722 (3 cylinder 20 hp), which has some nice features that the Yanmar lacks.

You could probably get some money for the 2GM, and even more if you rebuilt it...


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## Northeaster (Jan 13, 2007)

The engine is already out, as I wanted to check / replace the aging diesel tank, and clean up / repaint the engine compartment.
As the engine did work OK in general, and started immediately each time, it will probably last a few more years. My main comcern is putting cash into rebuilding (if necessary) a block that has been raw (salt) water cooled for 25 years.
My brother can:
a: Just clean it up, so I can put it in the freshly painted engine compartment.
b: try to do a compression test, although he will have to borrow the tools, ask someone to help, as his auto engine compression tools won't fit the diesel injector holes.
c: take an oil sample in for analysis, but it has been sitting for a couple months - would the oil sample be a true picture, as particles may settle out.
d: remove the head, so he can see the piston/ ring tops, valves, seals, and maybe see more of the block water jacket, to see if there are major corrosion issues. 

If he can check some of the above, and put it back together for a couple hundred bucks ( I need new engine mounts, approx $200 as well), then I will put it back in.

However, I think that if anything major need replacing, I would opt t oput my cash into a new engine, instead of one that old.

I would also like to know what the normal changes would be, in going form a 13hp engine, to a 21hp new one. Would that normally require a larger prop, different pitch, etc.
The 3YM20 is a couple inches longer, but I have room to push the shaft / prop towards the stern a couple inches. As well, I know a retired prop guy, who could probably shorten / rekey the shaft, if necessary.


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## JohnRPollard (Mar 26, 2007)

If you have gone to all the trouble of pulling the engine, you really should do more than "just clean it up". At a minimum, I'd have your brother do b,c, and d while it's out. Otherwise you may be re-installing an engine with little life left in it, or not, but you just won't know.

With a larger engine, I would expect that you'd need to re-prop (size and pitch). If you do go that route, this would probably be a good time to replace the shaft rather than re-use the old one.

If space is tight, the Beta equivalent is about 1.5 inches shorter and 1 inch narrower than the Yanmar.

I would suggest you peruse some of the re-powering threads here on Sailnet. There's usually quite a bit more to it than simply swapping the engines out....


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## Faster (Sep 13, 2005)

As someone mentioned already, shaft length may need to be changed, is the engine mount footprint the same? are there clearance issues on the "new" engine (height, width, accessories, access?) Going from Yanmar to Yanmar I'd hope most of these would be minimal, but if changing brands it can amount to a lot of work/money/both.

Sometimes even the angle of the engine beds needs to be altered.

I think you're right to be concerned about 25 years of RWC and its effects on the waterjackets... But realize the cost of the repower is always more than the cost of the engine itself.

Best of luck in your decision.


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## Northeaster (Jan 13, 2007)

I have definitely read alot of the repower threads. I realize that in many cases, when changing between different manufactures / models, there is often alot of extra work in adding / modifying the engine beds, etc.

In my case, if I change to the newer 2YM15, the current engine mount placement matches that of the new engine. Also, alot of the other measurements are similar, would not require a shorter shaft, and probably not any prop change - as the current 2GM is 13hP, and so is the new 2YM15.
So it would be an "easy" repower. I also have full access to crawl under the cokpit, to run the new wiring.

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.
Even this new engine matches the current engine beds, in width, and the front mounts are in the correct position. I would have to move the rear mounts back 3", but as I have good access, that is not a bad job.

I will have to check on the recommended exhaust hose size, with the larger 3YM20!!

John Pollard - I talked to my brother tonight, and he is going to take an oil sample for analysis, and pull the head, and oil pan off to have a look.

Faster - If I need a new shaft, I would have to get one. However, if it just needs to be shorter, my retired "prop guy" friend can likely mofify the currnet one to work fine. I may have to eat the cost of a new / used prop, but maybe nothing fancy for a year or two.


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## Northeaster (Jan 13, 2007)

John Pollard- Any idea of a price on the Beta Marine BD722?

Also, you mentioned advantages over Yanmar. Can you be more specific?


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## JohnRPollard (Mar 26, 2007)

Northeaster,

I got a price of $6800 for the BD722 when I inquired with Beta a month or two ago. That's not a whole lot less than your Yanmar 3YM20 price. But you'd have to study the specs to see what the respective prices include. For instance, the Beta price includes a new transmission, motor mounts, control panel, a PTO, etc.

Off the top of my head, some differences that I recall are that the Betas have built-in oil change pumps, shallow sump options, and glow plugs. Also, the Beta raw water pump is cam driven off the engine, so there is only a single belt (for the alternator and fresh water pump). 

Another consideration is that the Betas are based on the ubiquitous Kubota tractor engines, so the replacement parts tend to be cheaper and more readily available than Yanmar.


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## Northeaster (Jan 13, 2007)

John - Thanks for the info!

I am waiting for a call, form the Beta dealer in Maine, to get a price, just in case. I believe the Yanmar comes with all of the needed parts, as well, but I will double check. The price on the 3YM20 was about the same as your Beta quote!!($6900 in Nova Scotia, and in Maine, as the dollar is about even)

As far as installation, with both the Yanmar 3YM20 and the Beta BD722, I could use my existing engine bed / front mount positions, and would have move my rear mounts back 2-3".

I have decided to only repower if we find problems with the old 2GM, which will require putting more than a few hundred bucks into it!


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## TomandKarens34 (Dec 4, 2007)

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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## orthomartin (Oct 21, 2006)

*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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## Northeaster (Jan 13, 2007)

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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## Rockter (Sep 11, 2006)

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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## billangiep (Dec 10, 2003)

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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## Northeaster (Jan 13, 2007)

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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## Northeaster (Jan 13, 2007)

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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## billangiep (Dec 10, 2003)

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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## nomadman (Mar 31, 2009)

*2YM15 (14hp) - (2YM20 - 21hp) - 3YM20 (29hp)*



Northeaster said:


> (...)
> 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) à EUR 6060,-
3YM20 (21pk) à EUR 6950,-
3YM30 (29pk) à 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


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