Intermittent Water Flow - Yanmar 2QM15

Jason K · Post by **Jason K** » Mon Sep 17, 2007 2:57 pm

My Yanmar has been temperamental recently.

Sometimes it will start right up and run fine. Occasionally though, it will not pump water, often at inconvenient times. If it doesn't pump water, sometimes bumping the revs will get it flowing again.

This can occur right at start-up or after running for a little bit. It seems like it often happens after restarting the motor when we head back in.

I have changed the impeller, water pump belt, hoses, and the thermostat. The thermostat was pretty cruddy and I though it might have been sticking and causing the problem. However, the boat did the same thing this weekend with the new thermostat. I will be performing an acid flush next weekend.

A water pump would just fail, right? They seem pretty simple and it's hard to see how it would work intermittently.

Any ideas?

catamount · Post by **catamount** » Mon Sep 17, 2007 3:37 pm

Have you checked your engine zincs? There's on on the front of the engine (hose from pump comes in, bypass hose to thermostat goes out), and there's one on the back of the engine, near to the temperature alarm sender.

If the zincs are falling apart, maybe they are partially blocking flow through either the bypass or some part of the engine?

Noah · Post by **Noah** » Mon Sep 17, 2007 3:52 pm

You are sure the intake hose is clear? The PO had the same problem with the old Volvo on my Swede. It turned out the good looking raw water intake hose was collapsing on it's self in the middle. The thin rubber liner had separated from the heavier hose.

Figment · Post by **Figment** » Mon Sep 17, 2007 4:06 pm

Three powerboats on my dock had that collapsing/delaminated hose problem this year. All three drove themselves NUTS trying to figure it out because the problem was so inconsistent.

That hose isn't cheap, but it's a good place to start.

Jason K · Post by **Jason K** » Mon Sep 17, 2007 4:17 pm

Have you checked your engine zincs? There's on on the front of the engine (hose from pump comes in, bypass hose to thermostat goes out), and there's one on the back of the engine, near to the temperature alarm sender.

I replaced the one on the front of the engine, but I simply can't get the one in the back off. I've been shooting it with PB Blaster regularly and it won't budge. I haven't introduced heat yet, but I may have to. I'm having the same problem with the transmission dipstick. The front zinc had surface corrosion, but was about 95% intact.

You are sure the intake hose is clear? The PO had the same problem with the old Volvo on my Swede. It turned out the good looking raw water intake hose was collapsing on it's self in the middle. The thin rubber liner had separated from the heavier hose.

All three drove themselves NUTS trying to figure it out because the problem was so inconsistent.

The hose looks good, but it has not been replaced. I have only replaced the hoses on the motor itself. What's the best hose to use? Does anybody know a good source for the hose? McMaster?

Thanks!

catamount · Post by **catamount** » Mon Sep 17, 2007 9:24 pm

#218 wrote:[
The hose looks good, but it has not been replaced. I have only replaced the hoses on the motor itself. What's the best hose to use? Does anybody know a good source for the hose? McMaster?

I like the hardwall exhaust hose I got from Jamestown Distributors.

Quetzalsailor · Post by **Quetzalsailor** » Tue Sep 18, 2007 12:50 pm

Get on to the Yanmar site; theye're almost as good as this one:
http://www.freeboards.net/index.php?mfo ... _post&st=0

Perhaps a loose impellor blade is intermittently falling across an important passage; otherwise hard to imagine an intermittent waterflow cause. Well, maybe, a nasty floater in the intake side; a bit of weed or plastic bag. Hoses would collapse at high rpm/high load, not low.

Jason K · Post by **Jason K** » Tue Sep 18, 2007 2:17 pm

Thanks. The impeller is brand new and I've since inspected it trying to locate the source of this problem. I don't think the impeller is it. Also, I'm sure there is nothing blocking the intake side.

The intermittent flow happens both at startup and after running for a little bit. I think I'll replace the hose to be on the safe side and keep brainstorming in the meantime.

I would love to hear any other thoughts.

Also, thanks for the link to the Yanmar forum. There is a lot of good information there.

catamount · Post by **catamount** » Tue Sep 18, 2007 4:12 pm

Jason, I have a question -- how do you know that the engine is only pumping water intermittently?

On mine, water comes out the exhaust sporadically, but it keeps coming.

MikeD · Post by **MikeD** » Tue Sep 18, 2007 4:31 pm

Jason, I've also found the Yahoo Yanmar list pretty informative.

http://groups.yahoo.com/group/Yanmardiesel/

Jason K · Post by **Jason K** » Tue Sep 18, 2007 6:35 pm

catamount wrote:Jason, I have a question -- how do you know that the engine is only pumping water intermittently?

On mine, water comes out the exhaust sporadically, but it keeps coming.

Hi Tim,

When this occurs, it triggers the alarm buzzer. Also, there is simply no flow from the exhaust, even at higher RPM's. I am familiar with the discharge at idle, which sort of sputters, but this is almost no water exiting the exhaust.

David · Post by **David** » Thu Dec 13, 2007 2:25 pm

Jason,

Did you resolve this issue?

David

Jason K · Post by **Jason K** » Thu Dec 13, 2007 3:52 pm

David, thanks for asking. I meant to type a resolution awhile back but thought it would be bad luck given the intermittent nature of the problem. Then, I completely forgot about updating the thread.

Yes, the issue appears to be resolved. I replaced the intake hoses, both from the thru-hull to the strainer and from the strainer to the water pump (those hoses are freakin expensive!).

When I was doing that, I took a closer look at the strainer and noticed the older cork gasket looked suspect. I replaced that with a rubber one.

It seems to have fixed the problem. The motor has pumped water just fine since making those changes. I suspect the bad gasket was the problem, rather than the hoses. When I blew hard into the intake hose, I could force water to leak from the top of the strainer. So, an impeller, a thermostat, a lot of cleaning, all new cooling hoses, and several sessions of practicing sailing into the slip later, I'm inclined to blame a $3.00 gasket.

I love boats.

heartofgold · Post by **heartofgold** » Thu Dec 13, 2007 4:06 pm

So, an impeller, a thermostat, a lot of cleaning, all new cooling hoses, and several sessions of practicing sailing into the slip later, I'm inclined to blame a $3.00 gasket.

Yes, but you feel so much more secure knowing you have those new hoses, thermostat and impeller not to mention your advanced sailing skills, now don't you?

Jason K · Post by **Jason K** » Thu Dec 13, 2007 4:58 pm

heartofgold wrote:
So, an impeller, a thermostat, a lot of cleaning, all new cooling hoses, and several sessions of practicing sailing into the slip later, I'm inclined to blame a $3.00 gasket.
Yes, but you feel so much more secure knowing you have those new hoses, thermostat and impeller not to mention your advanced sailing skills, now don't you?

Well, there's no argument that these things all needed to be done. The PO had no maintenance records, so everything was suspect.

bcooke · Post by **bcooke** » Thu Dec 13, 2007 7:17 pm

Hey!

14 months with nary a peep and then you go posting as if not a day has passed?!

What black hole spit you back out Doug?

-Britton

heartofgold · Post by **heartofgold** » Fri Dec 14, 2007 11:02 am

Britton,

Nice to be missed! Especially when the welcome is phrased so warmly and eloquently.

Actually, I have been lurking in the shadows for some time, but my new job kept me away from the forum and the boat. Things suddenly settled so I felt it was time to climb out of the hold--I mean hole.

Plastic Classic Forum

Intermittent Water Flow - Yanmar 2QM15

Intermittent Water Flow - Yanmar 2QM15

Sporatic exhaust