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Old 11-12-2010, 20:19   #1
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Seawater Routing on a 3GM30FV

This is a V drive Yanmar with fresh water cooling installed in a Pearson 323. In looking over my cooling system I have discovered a potential problem, I think. On my boat seawater comes in the sea cock, to a large bronze strainer/filter, then to the V drive oil cooler, and then to the belt driven seawater pump, and finally to the heat exchanger.

I have a factory service manual with greasy fingerprints only in the V drive section of the manual. Evidence indicates the input shaft oil seal must have failed at some time.

At any rate, the picture below clearly shows that seawater should be routed to the seawater pump first, then back to the V drive oil cooler and then to the heat exchanger. It would appear my boat is siphoning water through the cooler instead of pumping it through as it should.

I've put about 30 hours on the engine out of a total of 1580. I don't know when this incorrect routing took place but the hoses look new and the pump has a new looking gasket on it as well. There has never been an indication of overheating.

Unless some of the experts here advise otherwise I'm going to reroute as indicated in the picture. Should I do this? Could any damage have been done if this arrangement has been in place since the repowering in 1989, 1580 hours ago?

BTW, the inspection of the system was predicated by a soft grounding last night where I spent several minutes in reverse stirring up the mud. Now I have very little water discharge out the stern. I suspect the bronze strainer/filter might be filled with silt, but I also found the pump belt very, very loose. I'll tighten that first then clean the strainer if needed.

Your thoughts and suggestions are much appreciated.

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Old 11-12-2010, 22:09   #2
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The only problem I can see with it routed the way it is, with all the joints/connections, that you have more of a chance of sucking air into the inlet before it reaches the pump. Also, if the inlet gets covered with seagrass it could suck air much easier.

If the sea strainer is of the proper separation media there shouldn't be any clogging problems.

You could back flush the v-drive system to make sure.

But yeah, I would re-route the hoses.
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Old 11-12-2010, 22:18   #3
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Thanks, that reason alone is worth making it right.

I have no maintenance log, so I'm planning a complete servicing of fluids, filters, impellers and whatever else is routine that I can think of. So I'll add this to the list.

The strainer is large and old school cool bronze. I have spare filters for everything else. I'm thinking the strainer doesn't have a replaceable filter and is merely cleaned and reassembled. I can't find any markings on the unit yet. Does that make sense to you guys for a sea strainer?

I might be taking it apart tomorrow if tightening the pump belt doesn't restore water flow out the back. It's barely pumping right now.
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Old 11-12-2010, 22:20   #4
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Just had a 4jh-te yanmar installed by yanmar dealer. They routed the seawater as you have it now, strainer, trans oil cooler is on the suction side of the raw water pump. I also questioned the wisdom of this routing before they did it, reply was it was "standard" practice. And, in my particular installation, the claim was it made for a more logical install in that seawater flowed in and out in a "U" path, there was less hose clutter. Since this is a yanmar dealer install and under a yanmar warranty, I dropped my questions.
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Old 11-12-2010, 22:24   #5
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I have a Yanmar with a Volvo hydraulic drive and a seawater cooled fridge condenser. The raw water enters at the through hul, goes thriought the fridge condenser, then through the cooling coil in the hydraulic drive and then to the raw water pump and on to the engine heat exchanger and then exhaust manifold and out...so basically same idea yoyu two guys have....its been like this for 125 years and no problems at all.

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Old 11-12-2010, 22:39   #6
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Chris, I considered similar reasoning to the Yanmar dealer. It certainly would cut down on the length of hose required, by almost two thirds if I'm picturing correctly in my head. Not to mention the extra clutter, but that certainly already exists on my boat. I'm still mapping it all out to get a handle on maintenance and troubleshooting.

But I wonder, if it's practical and logical merely because it saves the purchase price of the hose. Especially since it goes against the factory service manual specification. The water wouldn't "care" if it "U"s through the boat or "Z"s through in my opinion.

Just thinking out loud, not to be disagreeable.


Albro, well that's three in row this way. And yours is even more complex. Must be more common than I thought.

It just bugs me that the manual is different to my setup. And my Air Force training in maintenance is routed in being able to fix anything with the right tool and text combination.
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Old 11-12-2010, 22:43   #7
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Quote:
Originally Posted by chris07732 View Post
Just had a 4jh-te yanmar installed by yanmar dealer. They routed the seawater as you have it now, strainer, trans oil cooler is on the suction side of the raw water pump. I also questioned the wisdom of this routing before they did it, reply was it was "standard" practice. And, in my particular installation, the claim was it made for a more logical install in that seawater flowed in and out in a "U" path, there was less hose clutter. Since this is a yanmar dealer install and under a yanmar warranty, I dropped my questions.
It might be installed that way to reduce the amount of hose needed to accomplish the job, a cleaner looking system. But like I said earlier, the more joints the more chances of sucking air. Air will ruin a pump if not caught in a reasonable time.

The holes in the strainer screen should be about half the size of the cooler tubes.

As for Yanmar mechanics, well............ Being told I have to live with a problem, is not good practice to me.
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Old 11-12-2010, 22:59   #8
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My Yanmar goes through the remote v-drive before the pump. The engine was installed by the previous owner, so don't know if he checked if it was proper.

I would throw out that perhaps the picture shows a typical way of routing, or perhaps a preferred way of routing. I wouldn't say that a service manual is going to necessarily show all the permissable ways to do an installation. I would refer to an installation manual. If that says you must go to the pump before the v-drive then I would get more worried.

Pretty sure there's an installation manual on my boat.

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Old 11-12-2010, 23:13   #9
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Well, now that's four boats all with the routing reversed. That's really beating the odds so something is up with this.

My service manual is the old three ring binder style. Makes me wonder if there is a reason this practice might have changed over the years.

cal40john, if you happen upon the installation manual mentioned I'd be curious what it shows, and it's publication date.
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Old 13-12-2010, 11:40   #10
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My installation manual only says to minimize length of hose and bends. It doesn't say anything about v-drives, but remember mine is a remote v-drive so my install manual is for a 3GM30F not a 3GM30FV.
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Old 13-12-2010, 12:18   #11
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My installation manual only says to minimize length of hose and bends. It doesn't say anything about v-drives, but remember mine is a remote v-drive so my install manual is for a 3GM30F not a 3GM30FV.
To me, that would mean, put the thruhull/seacock/strainer as close to the pump as possible.
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Old 13-12-2010, 12:43   #12
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To me, that would mean, put the thruhull/seacock/strainer as close to the pump as possible.
Without drilling a new hole in the boat the OP has said that routing the v-drive to the pressure side of the pump would add hose length and bends. Most likely most changes would be on the pressure side and probably less of an issue. If re-routing results in small or no positive changes on the suction side and adds complexity to the pressure side I don't see much advantage.

Maybe pay a half hour to a company that installs engines with the correct install manual?

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Old 18-12-2010, 12:05   #13
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Thanks for the feedback.

I appreciate the input.

For now I intend to leave it as is, replacing a short piece of incorrect hose only.

thanks
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Old 18-12-2010, 12:44   #14
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I think leaving it that way is fine. I have seen a number of v-drive installations and I think all of them had the cooling water routed the same way. Chances are good that yours was like that from day one.
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Old 19-02-2012, 23:28   #15
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Re: Seawater Routing on a 3GM30FV

I found this post by chance, but it caught my interest. I have a 1980 Person 323 with the 3gm30FV. I also have the Yanmar manual. And from what I can see the plumbing I have is done to the manual, with a long hose running to the pump first (aft part of the engine) and then back to the transmission cooling.

I know this is an old thread, but thought the conclusions were a bit mixed. The guy who worked on this boat knew a fair amount and has done some great work so I just thought I would share that there is at least one boat with it done to the manual.

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