Yanmar 3YM30 overheating

[RichardS]

I've only run my 3YM30s at full peed on an couple of occasions but have never had an overheating problem. however perhaps I didn't run them for long enough.

I did notice that when I changed the coolant both crankcase drains were totally blocked with crud and the engines were only five years old and had been properly maintained. This suggests that they might be probe to coolant circulation problems unless plenty of prodding and flushing is undertaken.

Richard

 

[Beneteau381]

Thanks to everyone for suggestions.

Yes, with clean hull and clean prop (ie as now not long relaunched) I can achieve 3400 rpm at genuine 7.8 knots, but the engine will overheat in 5-10 minutes. Used to be it would only overheat occasionally, now it does it every time it is driven fairly hard.

No tee into inlet piping, and inlet deep underwater, pipe to Vetus strainer, then to engine.

There is a calorifier, on a fairly long pipe run. Does ALL the engine cooling freshwater go though this - I don't think so but am not an engineer? Worth trying a bypass pipe.

Have you taken out the heat exchanger stack? The outside of it being coated can cause just as much of a prob as the inside.

 

[Joljaz]

Thanks Everyone for some great new ideas! I don't know if my exchanger was ever replaced (guessing not). My eng. is #0744. I assume Yanmar is done with warranting them, or it would be tough to get them to fix for free. I have noticed on several occasions especially when running the brief 3400 that steam was coming from the exhaust port, I assumed it was outside air/humidity related. The water in the strainer at 2600 looks to be only 2-3" above the bottom, it's possible the occasional air bubble gets through. I like the idea about the hose from the ball valve to the strainer collapsing under suction, I'll replace it. Next time out I'll get a feel on that exhaust elbow too.

 

[Beneteau381]

Thanks Everyone for some great new ideas! I don't know if my exchanger was ever replaced (guessing not). My eng. is #0744. I assume Yanmar is done with warranting them, or it would be tough to get them to fix for free. I have noticed on several occasions especially when running the brief 3400 that steam was coming from the exhaust port, I assumed it was outside air/humidity related. The water in the strainer at 2600 looks to be only 2-3" above the bottom, it's possible the occasional air bubble gets through. I like the idea about the hose from the ball valve to the strainer collapsing under suction, I'll replace it. Next time out I'll get a feel on that exhaust elbow too.

the strainer should be full, sounds like you are sucking air through the seals on the top? My Vetus has a big O ring but also important is a little O ring under the wing nut

 

[Channel Sailor]

At low revs my strainer is usually full or a small air bubble in the top. At high speed I don’t recall it dropping to 2 inches above the bottom

 

[Joljaz]

the strainer should be full, sounds like you are sucking air through the seals on the top? My Vetus has a big O ring but also important is a little O ring under the wing nut

Thanks! I don't have a nut on top, I cracked the lid 2 years ago so the lid and O ring should be in good shape, but another thing I can check.
This is the type of strainer I have. The water shoots up and hits the lid, then falls to the 2-3" level making a lot of bubbles in the water. It's hard to tell if bubbles are getting sucked into the impeller. Wouldn't it be nice if the cover on the water pump was clear?

 

[Beneteau381]

Thanks! I don't have a nut on top, I cracked the lid 2 years ago so the lid and O ring should be in good shape, but another thing I can check.
View attachment 94581This is the type of strainer I have. The water shoots up and hits the lid, then falls to the 2-3" level making a lot of bubbles in the water. It's hard to tell if bubbles are getting sucked into the impeller. Wouldn't it be nice if the cover on the water pump was clear?
View attachment 94581

Ah subtly different from mine. I cleared mine the other day and when i slackened the top I could hear air going in and then the level dropped. So, does yours empty when the engine is stopped? If so, air may be getting in

 

[achwilan3]

Thanks Everyone for some great new ideas! I don't know if my exchanger was ever replaced (guessing not). My eng. is #0744. I assume Yanmar is done with warranting them, or it would be tough to get them to fix for free. I have noticed on several occasions especially when running the brief 3400 that steam was coming from the exhaust port, I assumed it was outside air/humidity related. The water in the strainer at 2600 looks to be only 2-3" above the bottom, it's possible the occasional air bubble gets through. I like the idea about the hose from the ball valve to the strainer collapsing under suction, I'll replace it. Next time out I'll get a feel on that exhaust elbow too.

Engines before #05566 experienced overheating problems, due to undersized heat exchanger. With some loud shouting, I got mine (engine #5421) replaced under warranty by the new one. But I must mention some resistance from Yanmar dealers... No problems since that time. Water level in the strainer is prone to variations related to lid air-tightness. You could use a bit of grease.

 

[Joljaz]

Engines before #05566 experienced overheating problems, due to undersized heat exchanger. With some loud shouting, I got mine (engine #5421) replaced under warranty by the new one. But I must mention some resistance from Yanmar dealers... No problems since that time. Water level in the strainer is prone to variations related to lid air-tightness. You could use a bit of grease.

Thanks. I assume it would be like pulling teeth, I'll try a few things before I contact them. How old was the engine when they did the work? Hours?

 

[Halo]

The strainer should hold the water in itself. If it drains back at all when you switch off the engine then the o ring is not sealing properly. Mine needs to be coated in Vaseline and very tight to achieve this.
If it is not sealed properly you will be drawing air into the system and may not be priming properly either.

 

[179580]

Chap at boatyard had same trouble with 3 cyl Yanmar. After a lot of various engineers failure to resolve it was finally cured by restricting flow through the calorifier. Some how the cooling water was making a preferential flow.

 

[achwilan3]

Thanks. I assume it would be like pulling teeth, I'll try a few things before I contact them. How old was the engine when they did the work? Hours?

Boat 2006; heat exchanger replaced 2009 (330h) as engine bilge blower was working continuously during previous seasons. I got information about this problem on US forums, as european dealers were kind of mute...

 

[Joljaz]

Thanks everyone for some great ideas. The hose from the through hull looks good, seems solid and has a wire in it hopefully to prevent collapse. I closed the through hull valve, coated the O ring with silicone grease and filled the strainer to the top with water. Water now stays about a 1/2" from top. It may be a while before my next long motoring journey, but a short trip of 30 min. produced no problem with 3-4 min. at full power. Although I replaced the coolant 2 years ago, It tested at only 10 below! this was surprising since it's "Long Life" coolant (is 2 years a long life?) Replacing coolant as soon as I get a Temp. gauge installed. Between these 2 fixes, I'm hoping problems are solved. If not, I'll take apart the exchanger for inspection and cleaning and add a valve to close off the calorifier on long motoring trips.

 

[KAM]

I don't have an overheating problem that I know about but I've been struggling with the wretched 3ym30 water pump for the last 10 years. I polish the cover plate every season. It's always been difficult to get it to prime at the start of the season and now seems to have got worse with a new impeller. Top surface of my inlet strainer is 700 mm above the intake so I'm probably expecting it to pump water up 500mm. The strainer doesn't hold water between runs. I don't see how it can be expected to given the crude nature of the plastic to O ring seal and rubber hoses with jubilee clips. Anyone know what the spec is on the pump. What sort of head can it pump. Maybe the strainer needs to be closer to the waterline.

 

[garymalmgren]

I'm probably expecting it to pump water up 500mm.
Anyone know what the spec is on the pump.

A marine engine raw water ( not fresh) circulation pump is positive displacement.
That means the water leaving the pump will positively push the water in front of it.
500 mm of a quite low head and any impeller driven positive displacement pump should handle this.
UNLESS, there is a restriction on the inlet (inlet strainer, inlet cock, inlet hose, inlet raw water filter, filter to pump hose.)
or on the outlet side ( everything from the pump outlet to the exhaust water )

I've been struggling with the wretched 3ym30 water pump for the last 10 years.
.The strainer doesn't hold water between runs.

I have used the term strainer for the grill that is fitted to the hull on the inlet of the engine raw water and filter for the unit between the cock and the pump.

Time to buy yourself a new raw water filter
No flow rate is given, but at that price I would give it a try.
US $14.95 25% OFF|SF SWF002 Cleaner Strainer Accessories Marine Intake Sea Water Filter Kayak Durable Replacement Mini Engine Cooling Raw Liquid|Marine Pump| - AliExpress


Gary

 

[KAM]

Ok so the Johnson spec for the pump says it can" lift up to as much as 3 metres dry" which means nothing particularly as they dont quote a speed. Maybe it needs more revs to get it primed. I'd be worried about reducing the life of the impeller by revving it too often dry. How long and at what revs do people run their engine at on start up before deciding theres no cooling water flow.

 

[Halo]

The strainer should stay full. If it does not then it is probably the root cause of your problem. You should try - New o ring , thick with Vaseline all round and tightened with a tool such as a forceps type device or one of those jar openers for old people.
If the water goes down 10mm or so then it’s the inlet side totally draining and leaving the delivery side full.

 

[Halo]

The vetus strainer has a lot to answer for

 

[Joljaz]

Update... A bright flashlight behind the hose from the strainer to the impeller shows air bubbles headed for the exchanger. The Water level in the strainer continues To fall. All through hull intakes on the boat have this plastic T fitted in, none of my friends know what it is for, I think a likely culprit. Anyone why it’s there?

 

[achwilan3]

Update... A bright flashlight behind the hose from the strainer to the impeller shows air bubbles headed for the exchanger. The Water level in the strainer continues To fall. All through hull intakes on the boat have this plastic T fitted in, none of my friends know what it is for, I think a likely culprit. Anyone why it’s there?View attachment 97658

Strange thing... I don't have it fitted on my Yanmar