Custom Engine Cooling Modifications: Backup Seawater Pump

[vertigo]

Hi, All.
This week I decided to explore the maintenance readiness of the seawater pump on my newly-acquired 2012 R-29s Yanmar 6BY2-260 engine. Engine coolant temperatures have been entirely normal on trips since we acquired the boat in November, but I have no information whether the original owner ever replaced the impeller, or how long it's been since the last replacement, so investigation was in order.

With my trusty assistant/chief engineer at wrench, we found that the factory-original pump was dripping from the front housing, indicating a failed mechanical seal. After much grunting and foul language from the chief engineer, the pump was out and on the bench for closer inspection to find that the impeller in all likelihood had never before been removed, and that the mechanical seal likely had failed a few hundred hours ago.

My initial inclination was to obtain an OEM replacement pump for installation, and to rebuild the failed pump for a spare when the new pump inevitably fails on a trip. But after watching the extreme discomfort of the chief engineer as he worked that pump off the engine, it became obvious to me that a combination of my size 2XL hands, the protective coating on my rock-hard abs, and my general distaste for working with my head lower than my ankles would combine to make it utterly impractical for me to ever plan to replace that pump at sea by myself.

That sobering reality brought me to where I am now, planning to engineer a redundant backup seawater pump into my engine's cooling system so that when the mechanical pump next fails, I can simply flip a valve and switch and have an electrical pump delivering seawater to my engine's cooling system until I'm safely back at the dock where chief engineer can repair the failed mechanical pump without the threat of emergency, and I can enjoy a cold beer while he works.

My current plan is to plumb ball valves and a tee into the seawater piping to connect a 12v washdown pump with quick connect hardware, and wire the pump so that it runs from a manual switch powered from a relay connected to the oil pressure switch, so that it can only operate while the engine is running (and perhaps with a manual override so that it can run even if the engine has ceased making oil pressure in an extreme emergency). That way I can have instant backup seawater cooling at all times if the main pump fails, and minimize the risk of a temperature-induced propulsion emergency. The cost of keeping spare electric washdown pumps is a tiny fraction of a spare Yanmar seawater pump for these BY-series engines, and if I'm feeling extra paranoid about loss of seawater cooling, I can always hook up two or three spare electric pumps in a standby array. :geek:

So, my question to the group is: have any of you done this sort of custom mod on your own boats? If so, I'd love to hear your thoughts and strategies. Or, have you thought about doing this mod and changed your mind, and if so then why?

 

[vertigo]

On the subject of rebuilding the failing mechanical seawater pump, I learned that the exorbitantly-expensive Yanmar pump is in fact made by Johnson Pumps for Yanmar, and that the parts have both Yanmar and equivalent JP part numbers, the latter being quite a bit easier to source. For example, the mechanical seal is JP part number 0.2247.022, and easily obtained, unlike its Yanmar cross-reference: 120650-42430.

Johnson parts list for the seawater pump (#10-13374) used in the Yanmar BY-series engines:
http://www.depcopump.com/datajohnson.php




Source for ordering Johnson pump parts:
https://www.pumpvendor.com/Johnson_Parts_List.html

At some point I'll try to cross reference the mechanical seals and the bearings back to their original manufacturers since Johnson Pumps likely doesn't produce those as unique items.

 

[BB marine]

Your plan may work if the if the wash down pump is not sharing the same sea strainer as the engine. My strainer is for both engine and wash down pump.

As far as a back up sea water pump, redundancy is always a good idea for safety. The sea water pump designs used in the Yanmar and Volvo are simple and for the most part very dependable. Like any rotating equipment there is wear and required preventative maintenance. The preventative maintenance comes in two forms Visual inspection for leaks, belt condition, and hose condition which should be done on a regular interval. The second is disassembly for inspection and replacement of damaged rotating parts. A minimum replacement should be the rotating element ( impeller) and O-ring. If a Mechanical seal is used and shows signs of leakage replace, or if lip seals are used and show evidence of damage or leak replace, if the internal wear plate or eccentric pump housing are worn its time for a complete pump replacement. The second inspection is recommended by the manufactures every 200hrs or 2 years (Volvo) I believe Yanmar is the same. If this is done the chances of pump failure are minimal but I suppose possible but any failure is possible at any time. Preventative maintenance is the key to reducing failures.

In the event that a pump failure does happen while under way because of a obstruction in the water pick up, bag, running aground ( sand and silt) and damaging the impeller. A back up pump would be great to have on board. It could be has simple as a large bilge pump with a bracket to submerge off the swim platform and run a hose to a connection in the raw water system (After the water pump, it can not be before the water pump). Or a more permanent installation that you described. Or keep a spare impeller on board and make modifications to the boat to ease in the repair of the pump. This was my method, If I have a pump failure ( damaged impeller) I can replace it in 10 minutes. The original boat design before interior modifications it was an hour. Good luck in your project, If having an additional back up pump gives you piece of mind while cruising it is a worth while project.

 

[vertigo]

Your plan may work if the if the wash down pump is not sharing the same sea strainer as the engine. My strainer is for both engine and wash down pump.
...
Or keep a spare impeller on board and make modifications to the boat to ease in the repair of the pump. This was my method, If I have a pump failure ( damaged impeller) I can replace it in 10 minutes. The original boat design before interior modifications it was an hour. Good luck in your project, If having an additional back up pump gives you piece of mind while cruising it is a worth while project.

Excellent points! My wash-down pump has a separate seawater strainer. I'm sure that I could not change that impeller myself in 10 minutes, and that when it fails I probably won't even have the luxury of that much time.

 

[knotflying]

Boat US towing insurance could be an alternative.

 

[vertigo]

Boat US towing insurance could be an alternative.

Perhaps in some locations and situations that would be a viable backup plan, but I would not be willing to rely on it to save my bacon in the many remote and rocky locations of Pacific Northwest waters. For some equipment failures there are simply no viable redundancy strategies, but this one seems readily doable, and not much more trouble than having a spare radio or reserve fuel.

 

[knotflying]

I would have 2 concerns with your idea if there was a pump failure. A) if you plan on pumping water before the impeller the impeller will prevent the water from entering the system. B) there won't be any coordination between how much water is being pumped and engine rpm. This could result in excess water backing into the cylinders via the exhaust valves. Just some thoughts that you may or may not have considered.

 

[BB marine]

Mike you are correct the auxiliary pump would need to be plumbed after the raw water pump housing outlet. The water flow would be more of an issue of not enough flow with a raw water wash down. The raw water pump used on my D3 pumps 1 cuft per minute = to 7.4 gallons per minute @700rpm. A raw water wash down has a max flow of around 5 gallons a minute at 40 psi 1/2" hose. If you were to attach a garden hose 1/2" id to the dock and run it to your strainer At 40psi it would flow 6 gallons per minute given the larger flow source is 100 ft away. Normally the garden hose can not keep up with the raw water pump. At 2000rpm my D3 raw water pump provides 2.7 cuft per minute= to 20 gallons a minute. So your thought of how much water will the auxiliary pump put out is a good Idea to check and match to the raw water pump capacity but most small 12 volt pumps will not provide enough water flow and engine rpm will be = to limp mode at best for proper cooling. At 3200 rpm the D3 pump flows 30 gallons a minute which in the Ranger/ Cutwater design with 1" hose attached to the thru hull it is hard to flow that much It really needs a 1 1/4" hose to be matched up properly to the Raw water pump.

Back in my marine technician days I had a customer that had a boat on a mooring with a damaged impeller. (stern drive) I needed to get the boat from the mooring can to the boat ramp about 5 miles away.( Taunton River MA. to Fall River launch ramp) I installed a 1000 gph bilge pump on a plate and mounted it to the swim platform support bracket at its lowest point. I had to lift the water up 5' to get to the location were I was teeing into the raw water side of cooling at the engine. This reduced my water flow 25% but still enough to be equivalent to the stern drive pump output running at 1000rpm. I was able to get the boat to the ramp without the cost of a tow for my customer. A very simple aux.pump to get a boat home.

 

[vertigo]

Mike you are correct the auxiliary pump would need to be plumbed after the raw water pump housing outlet. The water flow would be more of an issue of not enough flow with a raw water wash down. The raw water pump used on my D3 pumps 1 cuft per minute = to 7.4 gallons per minute @700rpm. A raw water wash down has a max flow of around 5 gallons a minute at 40 psi 1/2" hose. If you were to attach a garden hose 1/2" id to the dock and run it to your strainer At 40psi it would flow 6 gallons per minute given the larger flow source is 100 ft away. Normally the garden hose can not keep up with the raw water pump. At 2000rpm my D3 raw water pump provides 2.7 cuft per minute= to 20 gallons a minute. So your thought of how much water will the auxiliary pump put out is a good Idea to check and match to the raw water pump capacity but most small 12 volt pumps will not provide enough water flow and engine rpm will be = to limp mode at best for proper cooling. At 3200 rpm the D3 pump flows 30 gallons a minute which in the Ranger/ Cutwater design with 1" hose attached to the thru hull it is hard to flow that much It really needs a 1 1/4" hose to be matched up properly to the Raw water pump.

Back in my marine technician days I had a customer that had a boat on a mooring with a damaged impeller. (stern drive) I needed to get the boat from the mooring can to the boat ramp about 5 miles away.( Taunton River MA. to Fall River launch ramp) I installed a 1000 gph bilge pump on a plate and mounted it to the swim platform support bracket at its lowest point. I had to lift the water up 5' to get to the location were I was teeing into the raw water side of cooling at the engine. This reduced my water flow 25% but still enough to be equivalent to the stern drive pump output running at 1000rpm. I was able to get the boat to the ramp without the cost of a tow for my customer. A very simple aux.pump to get a boat home.

Thanks for that detailed consideration, Brian! Getting sufficient backup flow from an electric pump is definitely a challenge, and has me thinking of installing a more robust pump than the standard washdown unit, but even then I may have to consider it at best to be a short-duration emergency pump for a (hopefully-rare) situation where shutting down to change out an impeller is simply not an option.

 

[vertigo]

I would have 2 concerns with your idea if there was a pump failure. A) if you plan on pumping water before the impeller the impeller will prevent the water from entering the system. B) there won't be any coordination between how much water is being pumped and engine rpm. This could result in excess water backing into the cylinders via the exhaust valves. Just some thoughts that you may or may not have considered.

If I do this mod, I'll definitely tie in downstream of the mechanical pump, and will rig the switch so that the backup pump won't run if there's no oil pressure (except by automatically-reset manual override in the case of a simultaneous impeller and oil pressure failure during an in-route emergency. 😱, so that the next key cycle returns that backup pump to dependency on oil pressure. )

 

[vertigo]

Johnson parts list for the seawater pump (#10-13374) used in the Yanmar BY-series engines:
http://www.depcopump.com/datajohnson.php

A complete repair parts kit for this pump is available for $120 on Ebay:
https://www.ebay.com/itm/Major-Repa...KAAAOSwVsRcQLhh:sc:USPSFirstClass!98239!US!-1

The shaft bearings turn out to be standard bearings, #6203-2RS, 17 x 40 x 12mm, which can be purchased online quite commonly from many suppliers. If you want to buy the best, get Timken @ $8.95 each:
https://www.amazon.com/6203-2RSC3-6...mken+17x40&qid=1579835494&s=industrial&sr=1-2

Or, buy a lifetime supply of generic replacement bearings for $14.99:
https://www.amazon.com/dp/B01G7L3BN...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

Perhaps I'll start a series of posts: The Cheapskate's Guide to Yanmar Replacement Parts for Ranger Tugs (unless someone else is already doing that series. :roll: )

 

[knotflying]

What is the cost of the entire replacement assembly?

 

[NorthernFocus]

I considered a similar modification for the same reasons. We also operate around rocky shorelines in remote areas where it is typically too deep to anchor and time required to conduct repairs may not be available much less waiting for a tow. We ultimately opted for auxiliary power since it covers loss of primary power for any reason, not just cooling pump failure. That's a whole separate discussion but I do have a couple of thoughts on the pump scheme.

As BB marine pointed out there's no reason it won't work but likely won't provide enough flow for much above idle speed. Which is still way better than zero.

Regarding the design of such a system, I've been afloat all my life plus spent my career working on system reliability. And the one principle that nearly always holds true is that simple is more reliable. So if it were me I'd avoid all of the protective relays etc and simply valve it in. You'll only use it in an emergency when you're paying attention to what's going on so chances of leaving it running with the engine shut down are minimal. Relying on operator intervention is typically accepted as a valid design philosophy in reliability systems that don't involve potential for immediate threat to human life.

 

[knotflying]

I'll go with Dan's observation, keep it simple. This first started with a drip from the pump. This is definitely not a catastrophic event and can be dealt with once back to port. Granted that there is always something that can stop water flow and make you dead in the water, but there are many other components that can break and have the same results. Alternative propulsion would address any circumstance should it occur and seems to be a simpler solution. I also know of many a boater helped with a tow by a passing fellow boater.

 

[vertigo]

And the one principle that nearly always holds true is that simple is more reliable. So if it were me I'd avoid all of the protective relays etc and simply valve it in. You'll only use it in an emergency when you're paying attention to what's going on so chances of leaving it running with the engine shut down are minimal. Relying on operator intervention is typically accepted as a valid design philosophy in reliability systems that don't involve potential for immediate threat to human life.

That's exactly where my thinking has been leading me. The more I thought about devising relays, switches and bypasses, the more failure scenarios I could imagine that could thwart the value of the equipment in an emergency. I'd love to have a backup source of propulsion, but I can't think of how that would be practical on the R-29. And while it is impractical to plan to carry parts for major engine failures, it still seems simple enough to have at least some backup seawater cooling capability.

I'm leaning now towards a very simple manually-activated high volume washdown pump.

 

[vertigo]

Granted that there is always something that can stop water flow and make you dead in the water, but there are many other components that can break and have the same results.

Quite so, but some failure scenarios are more easily anticipated and insulated against than others.

 

[vertigo]

What is the cost of the entire replacement assembly?

:roll: Not sure. It's the impracticality of rapid replacement (with my big hands and well-appointed abdominal insulation) that motivates me to engineer an emergency standby system for the weakest link.

 

[vertigo]

Johnson parts list for the seawater pump (#10-13374) used in the Yanmar BY-series engines:
http://www.depcopump.com/datajohnson.php

A complete repair parts kit for this pump is available for $120 on Ebay:
https://www.ebay.com/itm/Major-Repa...KAAAOSwVsRcQLhh:sc:USPSFirstClass!98239!US!-1

The shaft bearings turn out to be standard bearings, #6203-2RS, 17 x 40 x 12mm, which can be purchased online quite commonly from many suppliers. If you want to buy the best, get Timken @ $8.95 each:
https://www.amazon.com/6203-2RSC3-6...mken+17x40&qid=1579835494&s=industrial&sr=1-2

Or, buy a lifetime supply of generic replacement bearings for $14.99:
https://www.amazon.com/dp/B01G7L3BN...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

Perhaps I'll start a series of posts: The Cheapskate's Guide to Yanmar Replacement Parts for Ranger Tugs (unless someone else is already doing that series. :roll: )

Here's a link to an inexpensive source for impeller replacement parts for the Yanmar BY series engines:
https://www.amazon.com/gp/product/B01BE ... UTF8&psc=1