Impeller Woes

[RoyS]

Have a 40 year old Yanmar 2QM15. Sometime in the past a P.O. converted this salt water cooled engine to fresh water with the addition of a second pump and a heat exchanger in a kit sold by Sendur. I now have two largely inaccessible water pumps belt driven on my engine. I change the impellers every two years despite the accessibility issue. Problems this year are as follows:
1. Cannot find gaskets for added pump. Exact same size as original pump with different hole pattern.
2. This year found both impellers damaged after two seasons use. One was missing a fin and both had torn cracked fins.
3. Purchased an impeller kit from Jabsco that was listed for the original pump. The provided gasket was clearly not for this pump. Every dimension was off.
4. The new

Jabsco impeller was correct in all critical dimensions but the fin thickness was greater than the original. Use or not?
5. As an experiment two years ago tried using a Nitrile impeller for salt water pump and continued using Neoprene for coolant pump. As stated above both impellers were damaged.
Anyway, now what? Is two year 200 total engine hours too much to expect? Never had failures this soon. Has Jabsco given up on quality control? Are the new thicker fins a design improvement or a defect? Use or not use?

 

[Rich Stidger]

As long as the bearings in my pumps (genset & aux) are good, I typically can get 250-300 hours on an impeller. However, since impeller failures are a PITA at best, I change out the impellers at the beginning of a season if I have 150 hours on them. I could have less if I had an impeller failure mid-season, so if the hours are under 100 hours I don't change.
I use Jabsco impellers pretty much exclusively. Although I have had numerous impeller failures, I have never traced a failure to a bad impeller. I have always found a different cause. As for the thicker fins, I have not noticed that dimension changing, and I am not sure I would notice unless the difference was substantial. I don't think I would worry about that dimension being bigger.

 

[Project_Mayhem]

Have you considered cutting out your own gasket? Most automotive stores sell sheets of gasket material

 

[Justin_NSA]

It's a shame that SpeedSeal went out of business. The kit makes it easy to inspect and/or replace impellers. Fortunately I have enough shims to keep mine serviceable in my lifetime.

 

[Blitz]

Ugh, first I heard. I'll probably get five years out of my spares.

 

[MitchM]

o i so love my speed seal. seems to me i need to get creative with form-a-gasket out of a tube if they are out of business selling gaskets... that being said , form a gasket came to my rescue for an on the water emergency replacement of the $$$ yanmar heat exchanger gasket, which tore when i removed the end cap of the ht ex to remove the piece of jabsco impeller that was clogging the tube and causing an engine overheat. .... get a tube from your local auto parts store, you won't be sorry..

 

[TimFromLI]

Be careful making your own gaskets, make sure the material is the right thickness. I tried using material that was too thick once and I couldn't get a prime. On my old Universal m25-xp about the thickness of a dollar bill was just right (actually some people use a dollar bill). Also those missing fins may be plugging the passage ways in your heat exchanger.

 

[jssailem]

some people use a dollar bill

Other than the ink, I would think a dollar bill is an excellent cotton fiber for a water gasket. Great cross weave with just enough crush-ability to seal two smooth metal surfaces.

 

[LeslieTroyer]

Just make sure the gasket material is the same thickness. To thick no suction, to thin or form-a-gasket material it will heat up like crazy and destroy the impeller.

 

[Charles Erwin]

Right. Make your own thin gasket - (thin paper bag or copy paper works fine.) The idea is the gasket is way thin thus to permit the impeller's outside face to come up firm against the cover plate. A very slight skim of rtv will seal any leaks. Even rtv alone can do the trick. Most important be sure both the plate surface and the backside (the surface at the bottom of the impeller bore inside the pump body) are dead flat - no ridges.

Charles

 

[RoyS]

Speedseal?

 

[jssailem]

Speedseal

A once clever solution to the pain of removing the cover of the raw water pump to change the impeller. Now a defunct British company due to the medical disability of the owner and maker of the Speedseal.

Too bad the idea could not be replicated and the solution carried on.

 

[Justin_NSA]

You'd think he could have sold the business. Maybe it just wasn't profitable.

 

[garymalmgren]

A couple of wad punches ( 5mm and 8 mm) a pair of scissors, a block of hardwood, two or three sheets of different thickness gasket material and you will never need to buy (hard to get) engine gaskets again.
Alternative gasket materials (in order of thickness) are copy paper, old chart paper and corn flakes box.
Thickness can be altered by doubling up on gaskets.
A dollar bill might be good material but the size is a bit limiting.
Suitable for water pump. fuel pumps, oil pressure sender. engine anode. thermostat. etc.

It is worrying that two (different types of impeller) failed after two years.
If there were the same I would suspect a bad batch. But in your case I have no answer.
Fit your replacements and keep an eye on the temp gauge?
Make sure your alarm is working if you have one.

Gary

 

[Davidasailor26]

A once clever solution to the pain of removing the cover of the raw water pump to change the impeller. Now a defunct British company due to the medical disability of the owner and maker of the Speedseal.

Too bad the idea could not be replicated and the solution carried on.

The pump on our 3YM30 uses an O-ring instead of a gasket. It doesn't have the thumbscrews of the speedseal, but impeller changes are still pretty painless.

 

[RoyS]

Fit your replacements and keep an eye on the temp gauge?
Make sure your alarm is working if you have one.

Had to chuckle at the suggestion of having a working alarm. I do not hear high frequency sounds very well, particularly with engine noise in the background. Years ago I fitted an electric boat horn to the engine over-temperature sender. The horn is in the cockpit locker under my helm seat. THAT I can hear!

 

[Capt jgw]

Other than the ink, I would think a dollar bill is an excellent cotton fiber for a water gasket. Great cross weave with just enough crush-ability to seal two smooth metal surfaces.

And cheaper than the real gasket. Those paper gaskets are a PITA, damn near impossible to remove without tearing them. If you remove the cover to inspect and decide the impeller's still good, you still need a new gasket. Form-a-Gasket does work. My boats original engine had the cover stuck on with it. I ran it two seasons that way and it didn't leak a drop till I opened it up.

 

[RoyS]

One might ask, how come my car's water pump lasts 100,000 miles and my boat's water pump lasts 150 hours?

 

[Davidasailor26]

One might ask, how come my car's water pump lasts 100,000 miles and my boat's water pump lasts 150 hours?

The pump in a car (and the one on the freshwater side of your engine) operates in a closed loop, and is a centrifugal, not positive displacement style. Because of that the impeller doesn't need to make direct contact with the walls of the pump body, so there is no friction point there to wear out. The raw water pump is better to have self-priming, so that one is positive displacement. Positive displacement pump vanes rub right against the pump body, and flex progressively as they turn. That's a lot more wear and tear on those vanes.

 

[LeslieTroyer]

One might ask, how come my car's water pump lasts 100,000 miles and my boat's water pump lasts 150 hours?

When was the last time you replaced your fresh water pump? In older cars with single skinny fan belts they would last 6-7 years - the newer serpentine belts don’t need as much pressure to keep them tight which greatly improves the life of the front bearing. Our little engines have much higher amps to HP ratio so the load is higher, and high belt tension kills the pump.

I Carry a spare pump - fresh as well as raw + extra impellers and rebuild kit for the raw pump