Yanmar Engine Impeller less than 5 year, monitor engine temperature

[callis...@gmail.com]

Reminder to watch your engine temperature when running and replace impeller before 5years 😊

 

At 2500rpm, our engine temperature is always around 158F.  On the way home, noticed the engine temperature was much higher than normal around 170F.  Throttled down, temperature dropped and thankfully made it back to the marina.  They confirmed the root cause, impeller fin broke!  See photo below, amazing one broken fin made the temperature rise that much.  My reminder to buy replacement part.

 

Happy Easter! 

SV Salvation #152

Claudia

 

 

 

[bill pittore]

Claudia,

 Were you or the mechanic able to retrieve the broken fin? If not it could be lodged somewhere between the pump and the heat exchanger. If it’s lodged in the hose it could limit water flow. BTW, I replace my impeller at the beginning of each season whether it needs it or not.

Bill

SV Navasana #77

<image001.png>

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[Claudia Allison]

Good point Bill, it was last fall so hard remember.  The mechanic found the issue and replaced.  Forgot to mention for reference, around 200 hours on the engine in fresh water.  

Sent from my iPhone

On Apr 20, 2025, at 8:08 AM, bill pittore <bill.p...@gmail.com> wrote:

Claudia,

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[Mike Maksimchuk]

I second - or third - Bill’s sentiment. I change it every year. 

On Apr 20, 2025, at 10:47, Claudia Allison <callis...@gmail.com> wrote:

Good point Bill, it was last fall so hard remember.  The mechanic found the issue and replaced.  Forgot to mention for reference, around 200 hours on the engine in fresh water.  

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[Jonathon Truwit]

Bill 

Do you disconnect the hose to the heat exchanger or remove the heat exchanger end cap?  Do you need to drain engine water ahead of time?  

thanks 

Jonathon

[bill pittore]

Jonathon,

To remove the end caps you would have to drain the engine coolant as well as raw water. On the back end cap there is a small drain valve that would drain raw water. For the coolant there is a drain on the hose that crosses in front of the alternator and then another drain on the starboard side of the engine with maybe a small drain hose attached. It certainly an involved project. I think I would do this, check the hose that goes from the pump to the exchanger. Also check the hose fitting on the pump and on the end cap.  If those are clear then I would not be too worried as the piece of impeller is small enough that it would not block too much of the exchanger. The alternative is to drain the coolant and raw water and remove the end cap to remove the piece. If you do decide to remove the end caps then you might as well remove the exchanger and clean out any crud. Also replace the o-rings Yanmar part # 128990-44100. I believe there are 4 of them. The parts drawing is not totally accurate for my engine. The pic shows the exchanger unit itself as a separate piece when on my engine it is attached to part #16 on one end so you have to pull it out from that end. I think it’s the rear of the engine, but honestly I don’t really remember. If it comes out the front then the alternator would need to be removed. I was changing out the alternator so I decided to go for it. Hope this helps.

Bill

:

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[Delbert Patterson]

Jonathon,

I have lost a water pump impeller blade on two occasions.  Both times, it just fell out of the hose at the pump outlet when I disconnected that hose from the water pump.  Just give the hose a good down hill slope so that the water draining back from the heat exchanger can flush it out.

Del Patterson

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[Jonathon Truwit]

Thanks Bill

I think for my skill level, I will take your recommedndation to just check hose and fittings.  Much easier than the latter, but I also appreciate the detailed instructions.   

I did think of opening seacock ever so briefly to flush out disconnected hose — turning over engine if needed (again briefly).  

Jonathon

On Apr 23, 2025, at 2:20 PM, bill pittore <bill.p...@gmail.com> wrote:

Jonathon,

To remove the end caps you would have to drain the engine coolant as well as raw water. On the back end cap there is a small drain valve that would drain raw water. For the coolant there is a drain on the hose that crosses in front of the alternator and then another drain on the starboard side of the engine with maybe a small drain hose attached. It certainly an involved project. I think I would do this, check the hose that goes from the pump to the exchanger. Also check the hose fitting on the pump and on the end cap.  If those are clear then I would not be too worried as the piece of impeller is small enough that it would not block too much of the exchanger. The alternative is to drain the coolant and raw water and remove the end cap to remove the piece. If you do decide to remove the end caps then you might as well remove the exchanger and clean out any crud. Also replace the o-rings Yanmar part # 128990-44100. I believe there are 4 of them. The parts drawing is not totally accurate for my engine. The pic shows the exchanger unit itself as a separate piece when on my engine it is attached to part #16 on one end so you have to pull it out from that end. I think it’s the rear of the engine, but honestly I don’t really remember. If it comes out the front then the alternator would need to be removed. I was changing out the alternator so I decided to go for it. Hope this helps.

Bill

:<IMG_20220413_124155.jpeg><IMG_20220413_124142.jpeg><Screenshot 2025-04-23 at 2.11.43 PM.png>

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[Jonathon Truwit]

Thanks Del — even easier.  

On Apr 23, 2025, at 2:35 PM, Delbert Patterson <delbert....@att.net> wrote:

Jonathon,

I have lost a water pump impeller blade on two occasions.  Both times, it just fell out of the hose at the pump outlet when I disconnected that hose from the water pump.  Just give the hose a good down hill slope so that the water draining back from the heat exchanger can flush it out.

Del Patterson

On Wednesday, April 23, 2025 at 02:20:54 PM EDT, bill pittore <bill.p...@gmail.com> wrote:

Jonathon,

To remove the end caps you would have to drain the engine coolant as well as raw water. On the back end cap there is a small drain valve that would drain raw water. For the coolant there is a drain on the hose that crosses in front of the alternator and then another drain on the starboard side of the engine with maybe a small drain hose attached. It certainly an involved project. I think I would do this, check the hose that goes from the pump to the exchanger. Also check the hose fitting on the pump and on the end cap.  If those are clear then I would not be too worried as the piece of impeller is small enough that it would not block too much of the exchanger. The alternative is to drain the coolant and raw water and remove the end cap to remove the piece. If you do decide to remove the end caps then you might as well remove the exchanger and clean out any crud. Also replace the o-rings Yanmar part # 128990-44100. I believe there are 4 of them. The parts drawing is not totally accurate for my engine. The pic shows the exchanger unit itself as a separate piece when on my engine it is attached to part #16 on one end so you have to pull it out from that end. I think it’s the rear of the engine, but honestly I don’t really remember. If it comes out the front then the alternator would need to be removed. I was changing out the alternator so I decided to go for it. Hope this helps.

Bill

:<IMG_20220413_124155.jpeg><IMG_20220413_124142.jpeg><Screenshot 2025-04-23 at 2.11.43 PM.png>

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[Jonathon Truwit]

To close the loop I did disconnect the raw water hose from pump and drained fluid from hose to heat exchanger and checked water pump outlet -  maybe found a fleck but not much so must be in heat exchanger 

I am sure most of you know this but I found the trick in this short you tube video helpful in disconnecting tubing 

https://youtu.be/-zAOsauYGGY?si=cYIJodPOC3WE_s0Z

Jonathon 

[Charlie Wing]

Jonathan,

When you disconnected the heat exchanger raw water inlet (3 screws) did you have a towel or something underneath to catch anything that fell out? I found mine had fallen before I could see it - only found it later when I removed the towel. 

Charlie

Sent from my iPhone

On Apr 25, 2025, at 3:38 PM, Jonathon Truwit <jonatho...@gmail.com> wrote:



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[Jonathon Truwit]

Charlie

I disconnected the exit side of the water pump and had it dangle down toward my oil drip pads under the engine.  They got wet (and of course did not soak up water) but did not see the fin. Certainly could have missed it, but did not see it when I mopped up water.  I followed the advice of Del and Bill and went for the simplest (and in my case safest) approach.  

Jonathon

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[Charlie Wing]

Hi Jonathon,

I may have missed a thread on this one but do feel it's important to find any missing pieces of impeller and not sure you found these yet? Removing the raw water pump exit hose wasn't enough for me to retrieve the piece. I had to disconnect the other end of the exiting hose ... Where it attaches to the heat exchanger. This didn't take too long as you really only have to rotate the alternator out the way to gain access. You will need a new o-ring for the endcap (part# 128990-44100, number 15 in the attached image). The blade fragment won't go in the element of the heat exchanger so it's most likely sitting there, but it could be blocking some of the ports.

Best

Charlie 

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From: catal...@googlegroups.com on behalf of Jonathon Truwit
Sent: Saturday, April 26, 2025 7:38 AM
To: catal...@googlegroups.com
Subject: Re: [Catalina 355:5692] Yanmar Engine Impeller less than 5 year, monitor engine temperature

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[Jonathon Truwit]

Thank you Charlie 

A little confused as Bill suggested if I remove the end cap I need to remove the coolant as well.  

Did you do this without removing coolant 

Jonathon 

<image001.png>

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<Heat Exchanger.jpg>

[bill pittore]

I guess it’s possible to remove the front cover and not get coolant leaking. I was removing the exchanger core so I had to drain the coolant. So if you look at the diagram I sent earlier the front of the exchanger is to the right in the picture. There are two o-rings labeled 15. The inner o-ring is what keeps the coolant separate from the raw water. When you remove the front cover you remove pressure holding the spacer #16 against the internal o-ring. That inner o-ring is around the core and sits inside the bore of the tank. In my second picture you can see where the o-ring sat on the core at the top, there’s some discoloration where the o-ring was. It might be tight enough that if you carefully remove the front cover you won’t disturb the inner o-ring and all is well.

Bill

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[Charlie Wing]

The access this way is only the raw water side. AF Coolant is isolated from the raw water in the heat exchanger (it’s the other side), so accessing this way will not require a coolant flush, no.

Let me know how else I can help

Charlie

Wing’n It

#20

Sent from my iPhone

On Apr 26, 2025, at 5:50 PM, Jonathon Truwit <jonatho...@gmail.com> wrote:

Thank you Charlie 

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[bill pittore]

Hi Charlie,

 Like I said in my last post it may be possible to remove the front cover and not get any coolant leakage but there is a risk it could leak coolant. I know this for a fact as I removed the exchanger from the tank and even though I drained the tank there was still some residual coolant and when I removed the front cover and loosened the inner o-ring some coolant leaked out. If you very carefully loosen the three screws on the front cover you should find out right away if the inner o-ring is going to keep the coolant sealed. 

Check out the attached picture. You can see the groove in the tank flange where the inner o-ring sits. That's what keeps the coolant in the tank. Once you loosen the cover screws there is no pressure on spacer #16 which presses the o-ring into the groove and around the exchanger core. 

Bill

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[Charlie Wing]

Thanks Bill,

I did need to put some force / pressure on the front cover by pulling the hose up (away from the cover), whilst it was attached. This broke the seal for the front part only - no coolant leak. Maybe I was lucky? Not sure if anyone has experience of this? I don't believe draining the cooling is such an issue so maybe this is the way to go(?). 

I'm hoping exchanging the impeller at the beginning of each season as regular maintenance going forward will prevent the need to do this. For me, my 355 was a purchase I made in July last year.

Thanks for the discussion

Charlie

Wing'n It

Hull #20

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[bill pittore]

I think that over a long time the o-rings get somewhat welded to their respective surfaces so when you removed the outer cap and its o-ring the spacer and inner o-ring stayed sealed. It’s not so bad draining the coolant; I think you’re supposed to do it every few years. The problem is filling it and getting all the air out of the system. 

Bill

On Apr 27, 2025, at 7:35 PM, Charlie Wing <charli...@gmail.com> wrote:

Thanks Bill,

I did need to put some force / pressure on the front cover by pulling the hose up (away from the cover), whilst it was attached. This broke the seal for the front part only - no coolant leak. Maybe I was lucky? Not sure if anyone has experience of this? I don't believe draining the cooling is such an issue so maybe this is the way to go(?). 

I'm hoping exchanging the impeller at the beginning of each season as regular maintenance going forward will prevent the need to do this. For me, my 355 was a purchase I made in July last year.

Thanks for the discussion

Charlie

Wing'n It

Hull #20

On Sun, Apr 27, 2025 at 7:19 PM bill pittore <bill.p...@gmail.com> wrote:

Hi Charlie,

 Like I said in my last post it may be possible to remove the front cover and not get any coolant leakage but there is a risk it could leak coolant. I know this for a fact as I removed the exchanger from the tank and even though I drained the tank there was still some residual coolant and when I removed the front cover and loosened the inner o-ring some coolant leaked out. If you very carefully loosen the three screws on the front cover you should find out right away if the inner o-ring is going to keep the coolant sealed. 

Check out the attached picture. You can see the groove in the tank flange where the inner o-ring sits. That's what keeps the coolant in the tank. Once you loosen the cover screws there is no pressure on spacer #16 which presses the o-ring into the groove and around the exchanger core. 

Bill

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[Jonathon Truwit]

Thanks Bill and Charlie

I did go out briefly yesterday — was going to race despite small craft warning, but 1/2 the boats out retired before start so race was abandoned.  On the way back we motored for a bit, temp was 170 for engine.  We live in lower Chesapeake.  Not sure where Claudia lives, but wonder if he is more north where water temp is lower.  Think I am going to hold on removing end cap for a while, as really want to be sure I need to tackle it.  But you both have described it well for me, so I should be able to do it.  Might also retry disconnecting at water pump again just to see if I get lucky.  

Jonathon

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[Jonathon Truwit]

Well my theory on higher raw water temp and engine temp is all wet, as David Mills is in FLA and runs at 158.  I went back, disconnected raw water from water pump exit, opened water pump and watched a screw driver come thru the orifice.  Draining raw water hose from Heat exchanger did not show fin.  Interesting after reconnecting i ran engine, albeit in neutral, at 2500 rpm and temp was 163-165. Went back to survey, temp was 160 at cruising and 163 at full throttle.  Attached is a video of my raw water exiting at 2500 - pretty brisk.  So I think everyone is correct, I need to take off end cap and see if a fin is plastered to HE, first need to order o-ring.  Must have moved fin a bit as temp is better (but engine not under load).  

thanks to everyone for your insights and explanations.  

Jonathon

[Jonathon Truwit]

looks like video is a picture.