Shelf life of impellers

[Project_Mayhem]

My boat came with a new raw water impeller in a box. Age is unknown. Does the rubber dry out over time?

Also, does the M25XP have a circulator impeller that needs to be replaced every so often?

 

[Davidasailor26]

Yes, unfortunately it does. I've had inconsistent experience with impellers, probably mostly due to their age after sitting on the shelf for a few years. Yanmar recommends replacement at 1000 hours or 4 years. I replaced one after about 5 years and it still looked fine so I saved it as a spare. The replacement, which had sat on a shelf for 2 years, only lasted another 13 months before losing a vane.

 

[Ralph Johnstone]

Also, does the M25XP have a circulator impeller that needs to be replaced every so often?

Sticking my neck waaaaaay out here but like a Yanmar, I would expect the impellor of the block circulator to be steel due to the toasty temperature of the antifreeze which rubber materials do not like.

 

[Project_Mayhem]

Thank you both.

@Ralph Johnstone I looked it up just after posting and discovered that you are correct

I will replace my raw water impeller AFTER winter layup. I've heard many technicians claim that the pink antifreeze destroys rubber impellers. Does anyone know of a source for impellers that's likely to rotate their inventory frequently?

 

[Ralph Johnstone]

Does the rubber dry out over time?

Same experience as @Davidasailor26 and installed a new Yanmar raw water rubber impellor after 10 years of use. It looked perfect when removed. Coated it with Meguiar's vinyl protector :

............ and sealed it in a zip lock baggy. Still looks great after 16 years and the new installed impellor still looks great is still going strong. I have to wonder if exposure to air (oxygen) is the culprit here.

 

[jssailem]

My boat came with a new raw water impeller in a box. Age is unknown. Does the rubber dry out over time?

From my experiential knowledge. Yes, rubber "dries out". However, these impellers are not made of "pure rubber". They are Polymer composites.

A Google search yielded this https://www.sciencedirect.com/science/article/pii/S2590123024000720. I was interested and it led me down a rabbit hole for 30 minutes.

An AI search provided me with this result in 1.2 seconds.

Material Degradation (Polymers/Composites)​

• Non-metallic impellers(e.g., PTFE, PVDF, polypropylene):
  • UV exposure (if stored near windows) → embrittlement.
  • Hydrolysis (moisture absorption) in humid environments → cracking.
  • Chemical outgassing or plasticizer leaching → dimensional changes.

My knowledge base was confirmed by data.

Finding a store with fresh products will be more difficult.

 

[BarryL]

Hello,

Let's discuss water pumps. You engine has two. One is the 'raw water' pump. This pump sucks up seawater (fresh water if you're in a river or lake, salt water if you're in an ocean, sound, bay, etc.). The other water is the 'coolant' pump. Just like a car or truck has a water pump to circulate coolant through the engine block, your Universal M25 has a water pump to circulate coolant through the engine block). Where the car has a radiator to cool the coolant, the boat has a heat exchanger. The automotive radiator is an 'air to water' heat exchanger, the marine heat exchanger is 'water to water' meaning that the seawater is used to cool the coolant. Note that the seawater and coolant never mix, they are kept separate inside the heat exchanger.

Note that your engine also has a thermostat (just like a car). When the coolant reaches a set temperature, the thermostat opens and allows the coolant to flow through the heat exchanger.

While the coolant pump can wear out and need replacement, that is pretty rare. Mote common is for the thermostat to fail closed. This will cause the engine to overheat. Signs of a bad coolant pump are leaks of coolant (not water) and an overheating engine.

Good luck,
Barry

 

[Richard19068]

Also, does the M25XP have a circulator impeller that needs to be replaced every so often?

@Ralph Johnstone I looked it up just after posting and discovered that you are correct
View attachment 235432

My understanding is a Universal M25XP is a Kubota D850. If that is correct you can get a whole new coolant pump from Kumar Bros for $32.89.

Kubota D850 Water Pump Parts for Sale - 15534-73030

Kumarbrosusa manufacturers and suppliers of kubota D850 watre pump tractor engine parts for sale with oem no. 15534-73030. Water Pump D850 used for kubota engine B1550D, B1550E, B1550HST-D, B1550HST-E, B6200D, B6200E, B6200HST-D, B6200HST-E, KH35 and many more.

www.kumarbrosusa.com

I used a Kumar coolant pump to replace the one on my M18 several years ago and it has worked just fine.

Of course you would want to verify the fit.

 

[StanleyJ]

I had good luck with a Kumar antifreeze pump on my Universal M12 engine. I always pull the impeller out of the freshwater pump and store it for the season rather than let it sit in pink antifreeze all winter.

 

[Dalliance]

Yes, impellers have a limited shelf life. Exposure to air and sunlight ages them quickly. I personally wouldn’t take a chance on an impeller of unknown age.

I’ve been using Jabsco brand from West Marine. Probably not the cheapest but I think a high volume stock turnover. I inspect them every year and replace them every other year. At approximately 80 engine hours per season, they always look like new when I pull them out. The brand new impeller goes in the pump and the two year old impeller goes into a zip lock bag in the nav desk as my emergency spare. To date, I’ve never needed the spare. If I ever do, it would be quickly replaced with a new impeller.

I don’t buy the notion that antifreeze deteriorates impellers or that they need to be pulled out during winter lay up. If antifreeze really deteriorated impellers, wouldn’t it also damage coolant water hoses? I leave my impeller in the pump, pickled in antifreeze over the winter with no problem. Not in the pink stuff though. I use the green -100°F marine antifreeze with lubricants and anti-corrosion additives for engines only. Same for the head. Pink -50°F only in the domestic water system.

 

[sailme88]

The impeller market was flooded a few years ago with "Nothing finah , made in China" impellers. Of course the very attractive price made them a popular acquisition. Everyone from resellers to boat yard stock rooms got some. The specific issue was a bonding problem between the brass hub and the rubber vane assembly. Some would fail shortly after installation, others a bit later into the season and then there were immediate failures. The lack or lessening of raw water discharge was/is a harbinger of failure. Diagnosing before installation came down to inserting needle nose pliers into the hub so that the key way fetches up on the pliers . Turning the vane ( or attempting to turn) would provide immediate feed back as to the viability of the impeller. If installed, the cover plate gets removed, and with the engine stop pulled, an assistant depresses the starter button while you watch the impeller turn. If the hub turns and the vane remains stationary or moves at a different speed.......then it is junk...

 

[Project_Mayhem]

Yes, impellers have a limited shelf life. Exposure to air and sunlight ages them quickly. I personally wouldn’t take a chance on an impeller of unknown age.

I’ve been using Jabsco brand from West Marine. Probably not the cheapest but I think a high volume stock turnover. I inspect them every year and replace them every other year. At approximately 80 engine hours per season, they always look like new when I pull them out. The brand new impeller goes in the pump and the two year old impeller goes into a zip lock bag in the nav desk as my emergency spare. To date, I’ve never needed the spare. If I ever do, it would be quickly replaced with a new impeller.

I don’t buy the notion that antifreeze deteriorates impellers or that they need to be pulled out during winter lay up. If antifreeze really deteriorated impellers, wouldn’t it also damage coolant water hoses? I leave my impeller in the pump, pickled in antifreeze over the winter with no problem. Not in the pink stuff though. I use the green -100°F marine antifreeze with lubricants and anti-corrosion additives for engines only. Same for the head. Pink -50°F only in the domestic water system.

Here's some info regarding antifreeze and material compatibility from Practical Sailor's Technical Editor:
A Marine Winterizing, Antifreeze, and Engine Coolant Primer

 

[Dalliance]

Here's some info regarding antifreeze and material compatibility from Practical Sailor's Technical Editor:
A Marine Winterizing, Antifreeze, and Engine Coolant Primer

Interesting article and a bit perplexing to me as it seems to contradict my personal experience over the last twenty years. I suspect the key is more my regular replacement schedule than which antifreeze product I’m using.

Could I get by with the pink -50°F stuff in my engine instead of the premium green -100°F? Probably. Most winters. But it’s my nature to almost always opt for the premium product for the added peace of mind. I consider it cheap insurance. Maybe I’m falling for an unethical marketing ploy on this one. I don’t know, but speaking of cheap insurance, I’ld hate to have an insurance claim for engine block freeze damage after a record breaking polar vortex and have to admit to my insurer that I used the less protective product. Am I wasting a few bucks every year for peace of mind? Probably… and I’m OK with that.

As for propylene glycol antifreeze stiffening neoprene impellers, I haven’t personally seen it. Inspection/Replacement is part of my regular spring recommissioning routine and the Jabsco impellers have always snapped back to their original shape when removed after two seasons of use and two winters pickled in antifreeze. Again, maybe that‘s my replacement schedule.

I can’t speak to the effect of propylene glycol antifreeze on nylon strainers as all mine are stainless steel because the nylon ones always struck me as something that wouldn’t last long, antifreeze or no antifreeze.

 

[Project_Mayhem]

Interesting article and a bit perplexing to me as it seems to contradict my personal experience over the last twenty years. I suspect the key is more my regular replacement schedule than which antifreeze product I’m using.

Could I get by with the pink -50°F stuff in my engine instead of the premium green -100°F? Probably. Most winters. But it’s my nature to almost always opt for the premium product for the added peace of mind. I consider it cheap insurance. Maybe I’m falling for an unethical marketing ploy on this one. I don’t know, but speaking of cheap insurance, I’ld hate to have an insurance claim for engine block freeze damage after a record breaking polar vortex and have to admit to my insurer that I used the less protective product. Am I wasting a few bucks every year for peace of mind? Probably… and I’m OK with that.

As for propylene glycol antifreeze stiffening neoprene impellers, I haven’t personally seen it. Inspection/Replacement is part of my regular spring recommissioning routine and the Jabsco impellers have always snapped back to their original shape when removed after two seasons of use and two winters pickled in antifreeze. Again, maybe that‘s my replacement schedule.

I can’t speak to the effect of propylene glycol antifreeze on nylon strainers as all mine are stainless steel because the nylon ones always struck me as something that wouldn’t last long, antifreeze or no antifreeze.

Here's another one regarding joker valves. I can confirm that Raritan and Jabsco are interchangeable
Joker Valves for Marine Heads - Practical Sailor

 

[Davidasailor26]

I use the green -100°F marine antifreeze with lubricants and anti-corrosion additives for engines only. Same for the head. Pink -50°F only in the domestic water system.

I use EG for winterizing my engine too, both for the reasons you mentioned and for more compatibility with rubber parts. But I’d suggest one caveat - only do this if you winterize in the water or somewhere that you can be sure to collect all of the antifreeze that discharges from the exhaust. As the article states marine toxicity of EG probably isn’t any worse than PG, but leaving a puddle of EG after winterizing on the hard would be very bad practice and potentially deadly to any passing animals.

 

[Dalliance]

I use EG for winterizing my engine too, both for the reasons you mentioned and for more compatibility with rubber parts. But I’d suggest one caveat - only do this if you winterize in the water or somewhere that you can be sure to collect all of the antifreeze that discharges from the exhaust. As the article states marine toxicity of EG probably isn’t any worse than PG, but leaving a puddle of EG after winterizing on the hard would be very bad practice and potentially deadly to any passing animals.

Good point. I always winterize in the water as soon as we arrive at my winter storage Marina. The engine has been running for at least five or six hours at that point, so I know it’s up to temperature and my antifreeze is actually going through the engine block rather than bypassing it. It’s a five minute job for me with a 3-way valve at the sea strainer and dedicated antifreeze/emergency bilge pump hose.
What brand of EG antifreeze are you using? I’ve been using the West Marine branded PG type with good results, but am willing to switch having seen the Practical Sailor articles now.

 

[Davidasailor26]

Good point. I always winterize in the water as soon as we arrive at my winter storage Marina. The engine has been running for at least five or six hours at that point, so I know it’s up to temperature and my antifreeze is actually going through the engine block rather than bypassing it. It’s a five minute job for me with a 3-way valve at the sea strainer and dedicated antifreeze/emergency bilge pump hose.
What brand of EG antifreeze are you using? I’ve been using the West Marine branded PG type with good results, but am willing to switch having seen the Practical Sailor articles now.

I just use regular EG from auto zone or wherever I happen to be before I winterize. My engine is freshwater cooled so the antifreeze is never in the block, just in the hoses, heat exchanger, and muffler. If it were a raw water cooled engine with the AF in the block I’d be more selective.

 

[Dalliance]

I just use regular EG from auto zone or wherever I happen to be before I winterize. My engine is freshwater cooled so the antifreeze is never in the block, just in the hoses, heat exchanger, and muffler. If it were a raw water cooled engine with the AF in the block I’d be more selective.

Thanks. Mine is raw water cooled.