fresh water/closed cooling system conversion

[woodster]

i have a 2qm15 yanmar engine ...it is raw water cooled at this time ......

has any one heard of a conversion or know of one that has been done to creat a closed system.....

..... i have it apart at this time ...head off,pistons and rods out and all the manifolds off and disasimbled .....so far everything mics out good and have bead blasted every thing but the block.....
...... and i am not planning on doing that.... just some dry cleaning in there....
.....will be putting new rod bearings and valve guides and rings...grinding valves and seats and lapping them in along with light honeing of the cylinder walls for seating the rings and rebuilding the injectors and of course new gaskets and seals ........

any thoughts or comments

regards
woody

 

[Ed Schenck]

Fresh water conversion of 2QM

My old 2QM20 was converted by a previous owner. The heat exchanger was still available a few years ago when I was looking to convert a 3QM30. But I cannot tell you where I found it. The other expense is the pump. These parts are clearly seen in the accompanying pictures.

 

[woodster]

thanks for the pics ED ......i am wondering how that worked keeping the hot water tank for the fresh water system ......and did you have any complantes with the conversion....

 

[yottyboy]

You don't need a brand specific heat exchanger, just one big enough to handle the engine. You will want a cooler thermostat, 160 degree. As long as you can figure out the plumbing and a way to bracket the monster securely, it's no big deal.

 

[Roger Long]

You don't need a brand specific heat exchanger, just one big enough to handle the engine. You will want a cooler thermostat, 160 degree. As long as you can figure out the plumbing and a way to bracket the monster securely, it's no big deal.

Nothing is a big deal as long as you know how to do it right. In this case, that means knowing how to arrange the piping so there are no high spots to create air locks or pump cavitation. Mounting an additional pump so it's belts and operation are as reliable as you want your engine to be, etc.

Buying all original Yanmar parts to convert to the FW cooled version of the engine would eliminate many concerns but they probably aren't available and it would be expensive.

If you had to ask this question here, you need much better advice and information than you will get here. Failure of this system could toast your newly rebuilt engine.

 

[woodster]

thanks for the input fellas .....i have a general idea of what it needs and how i want to do it ....but it never ever hurts to get input from the vets on here ...as i have seen in othere topics posted on here.... this is a very diversed group of hands on sailors/inavators....imho one can learn from each and every one here at one time or another......

regards
woody

 

[Ed Schenck]

About the hot water tank Woody. Yes, it heated water just as well as my new 3YM30 does. The boat had a VDO instrument panel with all the gauges. So I know that the temperature was correct. As already mentioned it requires the 160 degree thermostat.

I wish I had a picture or could remember the details of the pump mount. Sticks in my mind it was about a 4" length of one inch angle iron. Somehow it bolted to the case. No adjustment, that is done with the alternator.

 

[Bud22569]

Have you considered replacing the cylinder liners while you have it torn down? Just to share a hard lesson learned by me. A while back I rebuilt my YSM12 and decided not to reline the cylinder. I honed the old liner so that the new rings would seat properly. So 50 hours after the rebuild I ended up tearing it down again to put a new liner in to resolve compression problems. On my engine, replacing the cylinder liner was not difficult and relatively not too expensive in the scheme of the whole rebuild. I believe I paid ~$90 for a liner from Mastry Marine.

One deceptive item on a new cylinder liner on the YSM12 is that the very top of the cylinder liner is machined out to a larger bore than the rest of the cylinder. When the liner is worn out there will be no lip at the top as you see in engines that have the same bore from top to bottom. I don't know if all old Yanmar cylinder liners are bored like this or not. Perhaps someone here who is familiar with your engine can chime in on this.

 

[Rob19574]

Woody - check with mac boring in NJ. They have an excellent Yanmar tech support line you can call to help with your to-do list here. Bounce any ideas off them or perhaps even use them for parts. 866.526.9717 or 908.964.0700. Mac Boring is the regional Yanmar distributor.

 

[sailaway78]

What will you gain

My question is what do you hope to gain. Apparently, from reading your post, you have the mechanical abilities to do the conversion. But there is very little benefit to be gained. With fresh water cooling, you can run the engine hotter, which will make it run a little better. This is the only benefit I can see. Other than that, you are going to have to spend a lot of money, do a lot of work, and have more things that can go wrong. Being fresh water cooled does not make the cooling system more reliable, nor does it necessarily make the engine cool any better. It has worked like this for twenty five years or more. Is hard to improve on that.

 

[tommays]

One of the issues with changing and old motor to FWC is the risk of scale flakes cloging the exchanger tubes

 

[woodster]

Nice N Easy
Seidelman S37
Slidell, La.


Joined: May 2005
Posts: 2,255

What will you gain

Top
My question is what do you hope to gain. Apparently, from reading your post, you have the mechanical abilities to do the conversion. But there is very little benefit to be gained. With fresh water cooling, you can run the engine hotter, which will make it run a little better. This is the only benefit I can see. Other than that, you are going to have to spend a lot of money, do a lot of work, and have more things that can go wrong. Being fresh water cooled does not make the cooling system more reliable, nor does it necessarily make the engine cool any better. It has worked like this for twenty five years or more. Is hard to improve on that.



the issue at hand is that i am concerned about the hot water heater being heated well for the shower and sinks when off shore power....after i learn how to sail this boat with confidence i plan to move around a lot on the gulf and the east coast ....it may well be worth my while to repower with a 20hp or so fresh water cooled ....but haveing said that i still have a perfictly good 15 hp raw water cooled that will be in very good repair after the rebuild ....as it looks from the history of the 9.2 they went to 20 hp in the later years of manufacturing ...in my minds eye there was a very good reason for ding so ei ...maybe under powered and i am assuming that the hot water system suffered some with the old 15 hp modle in the boat as well but if i find that it heats the water well then i will fore go the power upgrade till a later time ...i am in no means in a hurry to put the boat in the water till it is up to my desired configureation ....i feel the more i do now the less i will have to do in the water later on ....not trying to build a hilton style boat ....i am of the mind the KISS theiory is the best way to go ....i know there is no bullet proof boats out there but if i do the best i can now then the maintance will be a lot less stressful in the long run....and anything worth having is worth working for and will be appreciated better and longer.......

regards
woody

 

[sailaway78]

Hot water heater

My previous boat had a 2QM15, but did not have a hot water heater, so I cannot reply with any knowledge to that. Current boat has a 3GM raw water cooled, and I can tell you that it makes HOT water. But, only when running hard. If you expect to run the engine while at anchor, to make hot water, it will not work. Mine will not get much above luke warm unless you actually run it pretty hard under load. I cannot attest to a fresh water cooled engine and how it will heat hot water. For what ever it's worth, I no longer have the water heater hooked up to the engine in any way. I do quite a bit of offshore, and long distance cruising. Usually anchoring out. I have found that with a source of hot water, or even warm water on board, I use waaaaaaaay too much water. So, I now just use a spit bath, with water heated up on the stove, or solar shower for bathing. My water consumption is cut by a tremendous amount, allowing more time away from marinas and spent in more remote areas.

 

[rardiH36]

140F vs 160F Thermostat Housing - QM Engines

One item to include in your decision tree is that the QM series exhaust manifold for the raw water cooled engines will only accomodate the ~140F thermostat. The ~160F thermostat won't fit. My 2QM20 was converted by a PO from a raw water to a coolant system by the addition of a belt driven pump and an externally mounted heat exchanger. I tried for a while to seek out a way to increase to a 160F thermostat, but nothing came up. I mention because if one reason for the conversion is to heat the domestic water, keep in mind that the heat content provided to the water heater by the engine will be lower than with engines that are designed from the get-go with a self contained ~160F system. When idle, the anti-freeze flowing into my heat exchanger from the engine becomes very warm, but not hot enough to burn a finger-tip.

As to engine temp and performance, all I know is that the ~140F 2QM20 has been powering my boat since 1980 and its still working just fine.

regards,
rardi