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Old 17-11-2019, 06:14   #1
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Yanmar 3YM30AE with SD25 raw water flow issue

Hello,

one of my engines with only 450 hours recently started to produce "white smoke" when revving under load over 2,000 RPM.

What did I do to troubleshoot:

1) I changed the impeller, even if the old one looked totally fine.

2) I cleaned the raw water strainer filter

3) I checked the impeller belt tension and it looked fine.

4) I cleaned the Sail Drive inlets.

5) The coolant level is fine.

6) I changed engine oil and filter, the color was fine.

7) I opened the heat exchanger cap, sucked up some coolant with a syringe, filled up a small bottle, the color was fine.

8) I started the engine looking into the heat exchanger filling hole to see if there were bubbles, there were not.

9) I compared the running temps measuring them on top of the heat exchanger with a gun, and here are the numbers:

Port (problematic engine)

At 1,500 RPM temp 147F
At 2,000 RPM temp 153F

Starboard (good engine)

At 1,500 RPM temp 149F
At 2,000 RPM temp 153F

I measure the water coming out of the exhaust while at idle, and both engines were delivering the same quantity and no white smoke was coming out of the port engine. I thought the problem was solved but, when underway at 2,000RPM the problem reappeared.

9) I then measured the quantity of raw water coming out of the exhaust while underway:

Port (problematic engine)

At 1,500RPM 2 minutes 14 seconds to fill a bucket

Starboard (good engine)

At 1,500RPM 53 seconds to fill the same bucket

Port (problematic engine)

At 2,000RPM 1 minute 37 seconds to fill the bucket

Starboard (good engine)

At 2,000RPM 33 seconds to fill the same bucket


It seems like the problem is not enough raw water in the system. Could it be an occlusion in the heat exchanger?

What can I do to check it and clean it? I read somewhere that sucking a bucket of vinegars in the raw water system and letting it stay overnight would help cleaning it.


Has anybody done that? Any other suggestion?
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Old 17-11-2019, 07:31   #2
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Re: Yanmar 3YM30AE with SD25 raw water flow issue

Could be buildup in the exhaust elbow.
I'm going through something similar, that and small pinhole leaks in my exhaust hose. In the process of changing it all out.
With that low of hours, your hose should be fine, but Could be worth checking that all clamps are tight down your hose lengths too.
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Old 17-11-2019, 08:56   #3
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Re: Yanmar 3YM30AE with SD25 raw water flow issue

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Originally Posted by chris mac View Post
Could be buildup in the exhaust elbow.
I'm going through something similar, that and small pinhole leaks in my exhaust hose. In the process of changing it all out.
With that low of hours, your hose should be fine, but Could be worth checking that all clamps are tight down your hose lengths too.


Thanks Chris! I forgot to mention that my bilge is totally dry.
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Old 17-11-2019, 12:42   #4
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Re: Yanmar 3YM30AE with SD25 raw water flow issue

I'm envious! Mine is slowly getting better
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Old 17-11-2019, 13:17   #5
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Re: Yanmar 3YM30AE with SD25 raw water flow issue

Good comprehensive descrition of your engine symptoms B4A.
Except it sounds like steam & not white smoke although I see u put that in inverted commers. Certainly your difference in flow rates points to the problem.
Check the thru hull is clear first off before you acid flush the heat exchanger. You can find a vid on youtube of how to flush raw water system or there will be a thread on CF. Use google custom search.
Problem may well get worse if you don't find the cause soon as if the raw water gets too hot in the heat exchanger the buildup will accelerate.
Post back what you find
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Old 17-11-2019, 14:56   #6
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Yanmar 3YM30AE with SD25 raw water flow issue

I would definitely pull the heat ex stack and check for blockages, then move onto the exhaust elbow.
Good news is your engine isnít overheating, but you do have I believe a water flow problem that needs resolving.

Have you ever had an impeller fail before?
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Old 17-11-2019, 15:20   #7
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Re: Yanmar 3YM30AE with SD25 raw water flow issue

You have two engines so you can swap components if necessary see if the fault transposes to the other engine. Maybe the raw water pump is the easiest to start with.
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Old 17-11-2019, 15:34   #8
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Re: Yanmar 3YM30AE with SD25 raw water flow issue

Quote:
Originally Posted by Compass790 View Post
Good comprehensive descrition of your engine symptoms B4A.
Except it sounds like steam & not white smoke although I see u put that in inverted commers. Certainly your difference in flow rates points to the problem.
Check the thru hull is clear first off before you acid flush the heat exchanger. You can find a vid on youtube of how to flush raw water system or there will be a thread on CF. Use google custom search.
Problem may well get worse if you don't find the cause soon as if the raw water gets too hot in the heat exchanger the buildup will accelerate.
Post back what you find
Compass, you are right on the money.

After a lot of sleepless nights thinking about the problem, I had the genius idea: It is something to do with the quantity of raw water. I new I cleaned the three lateral raw water inlet on the SD25 sail drive really well. Let's test them.

According to the Useless Owner's Manaul, there is only 1 inlet on a SD25 sail drive:



Let's see if this plugged, regardless that I thought I cleaned really well. I stuck my SUP pump into the sail drive inlet at the raw water filter:



While my wife was pumping, I dived and checked where the bubbles were coming from.

To my surprise, there was a very thin stream of bubbles coming from the back of the sail drive. Right here:



I stuck a long thin screw driver in it, and there was a lot of growth coming out.

That, was the problem!

Compass was right on the money. At high RPM, the quantity of water sucked by the inlets shown in the Useless Sail Drive Manual was just not enough. The white smoke was just vaporized water. There was an undocumented second "secret inlet" on the sail drive. If I didn't pump air from above, I would have never found it out.

Anyways, after cleaning the long (more than 10 inches) channel in the back of the sail drive, I tested again the quantity of the water from the port exhaust at 2,000 RPM and it was 1 bucket in 33 seconds. Just like the one on the starboard.

Problem solved.

The Yanmar guy I spoke to describing the problem said it was a blown head gasket. Replacing a head gasket is a lot of $$$.

I am so happy I was able to trouble shoot the issue.

Shame on Yanmar for not documenting this "secret" raw water inlet.

All is good what ends good. Hope this can serve well other SD25 owners.
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Old 17-11-2019, 15:58   #9
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Re: Yanmar 3YM30AE with SD25 raw water flow issue

Excellent troubleshooting B4A, well done.

It seems at times that "replacing the head gasket" is the standard response to every engine problem
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Old 17-11-2019, 21:51   #10
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Re: Yanmar 3YM30AE with SD25 raw water flow issue

Thanks for posting your trouble shooting with the diagram. I always like to know the outcome. Good you got it sorted any way. It amazes me what clogs the water intakes, we have had oysters growing in there & on the 2hp outboard it can get clogged with the eggs & little jellys that are thick in the water in summer as it has very narrow water galleries.
The moment it starts steaming you know it's time to take action.
Another good thing to do is have a strainer after the raw water pump to catch impeller blades before they get into your heat exchanger or block if raw water -cooled.
Lucky you ignored the Yanmar "tech" & got a cheap fix.
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Old 18-11-2019, 12:05   #11
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Re: Yanmar 3YM30AE with SD25 raw water flow issue

Quote:
Originally Posted by B4A View Post
Hello,

one of my engines with only 450 hours recently started to produce "white smoke" when revving under load over 2,000 RPM.

What did I do to troubleshoot:

1) I changed the impeller, even if the old one looked totally fine.

2) I cleaned the raw water strainer filter

3) I checked the impeller belt tension and it looked fine.

4) I cleaned the Sail Drive inlets.

5) The coolant level is fine.

6) I changed engine oil and filter, the color was fine.

7) I opened the heat exchanger cap, sucked up some coolant with a syringe, filled up a small bottle, the color was fine.

8) I started the engine looking into the heat exchanger filling hole to see if there were bubbles, there were not.

9) I compared the running temps measuring them on top of the heat exchanger with a gun, and here are the numbers:

Port (problematic engine)

At 1,500 RPM temp 147F
At 2,000 RPM temp 153F

Starboard (good engine)

At 1,500 RPM temp 149F
At 2,000 RPM temp 153F

I measure the water coming out of the exhaust while at idle, and both engines were delivering the same quantity and no white smoke was coming out of the port engine. I thought the problem was solved but, when underway at 2,000RPM the problem reappeared.

9) I then measured the quantity of raw water coming out of the exhaust while underway:

Port (problematic engine)

At 1,500RPM 2 minutes 14 seconds to fill a bucket

Starboard (good engine)

At 1,500RPM 53 seconds to fill the same bucket

Port (problematic engine)

At 2,000RPM 1 minute 37 seconds to fill the bucket

Starboard (good engine)

At 2,000RPM 33 seconds to fill the same bucket


It seems like the problem is not enough raw water in the system. Could it be an occlusion in the heat exchanger?

What can I do to check it and clean it? I read somewhere that sucking a bucket of vinegars in the raw water system and letting it stay overnight would help cleaning it.


Has anybody done that? Any other suggestion?
Since you changed raw water impeller I would definitely look at your heat exchanger raw water galleries.
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Old 18-11-2019, 13:55   #12
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Re: Yanmar 3YM30AE with SD25 raw water flow issue

I have Sd20 sail drives on my L40 and they ONLY suck water through the bottom hole. None al all though the sides. You need to keep it clean and be careful when you beach your boat as mud can go inside and this creates a mess in the pumps (and obviously) wear in the pump.
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Old 20-11-2019, 01:06   #13
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Re: Yanmar 3YM30AE with SD25 raw water flow issue

In my experience, white smoke is either unburned fuel, oil getting into the air intake, or a new pope has been chosen.
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Old 20-11-2019, 10:52   #14
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Re: Yanmar 3YM30AE with SD25 raw water flow issue

Quote:
Originally Posted by Mike Banks View Post
In my experience, white smoke is either unburned fuel, oil getting into the air intake, or a new pope has been chosen.
I would agree with you. The white smoke and reduced raw water, on one engine, would seem to be two issues?
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Old 20-11-2019, 17:04   #15
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Re: Yanmar 3YM30AE with SD25 raw water flow issue

Quote:
Originally Posted by Cadence View Post
I would agree with you. The white smoke and reduced raw water, on one engine, would seem to be two issues?

I think the OP mistakenly described steam as "white smoke" as he said cleaning out his raw water intake pathway fixed his problem.
Hopefully he posts back if that is not the case.
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