Time has come to rebuild my Yanmar 3GM30F Raw Water Pump.
The seal was ready to fail, because the circular compression spring was rusted through and the shaft was pitted under the seal lip.
One vane on the impeller was cracked and there wasn’t much water coming out of the exhaust.
The new seal wasn’t expensive at USD 7.70 , nor were the two ball bearnings at USD 4.75 each., but ouch the new shaft was a whopping USD $ 125.00 .
Re-assembly was easy until I read the proceedure from Nigel Calder’s book, which states to use a Teflon Based Waterproof grease to lubricate the new impeller.
I also read the Don Casey Library which says to use Petroleum Jelly.
So my question now is which grease to use ?
The replaced impeller is an original equipment Yanmar impeller and I don’t know what it is made of, does anyone know ?
I expect to use this pump as a replacement “Ready To Go” spare, so it will set on the shelf for a long time, and I don’t want the wrong grease deteriorating that new impeller.
B T W , it is most difficult to find Teflon Based Waterproof Grease, here in Singapore , still haven’t found any locally yet !
Petroleum jelly has been the “standard” fo many years, but the material of impellers has changed from a rubber to a neoprene product.
If the impeller you have is neoprene, it would be better to use teflon based grease. This is a DuPont product, readily available in the YS for about $16.00
The most likely place to find it, in any country, is at a plumber supply warehouse.
So my question now is which grease to use ?
I use Johnson Pump impellers which are nitrile rubber and come
with a little packet of glycerine.
I expect to use this pump as a replacement “Ready
To Go” spare, so it will set on the shelf for a
long time, and I don’t want the wrong grease
deteriorating that new impeller.
Don’t insert the impeller into the pump until you need to use it.
Hi John and Norris , T Y , for your replies . I do have reason to stock a "ready to go " raw water pump for my Yanmar, because I have already been caught out without one ready to install, and that was very near a lee shore, was a reef next to the shipping channel while transiting the Great Berrier reef on the N E shore of Oz .
There was no extra time to insert an impeller then re-install the pump when the wind and current was pushing me ashore on to the reefs there ! I needed a “ready to go” pump, at hand , and since I had that , me and my boat avoided another disaster.
Yes, I do understand what Norris recommends,and it is a good reccommendation , but I don’t have the bucks to stock an extra 3rd pump body with the impeller removed .
Since I don’t have a clue as to what rubber Yanmar uses for it’s impellers, I choose to side on caution and use an impeller lubricant that will not swell and bind the rubber impeller, what ever it is made out of , when it is needed the most, as in an emergency .
Oh my Gosh , Yes , I do have emergencies like this , too ! I have suffered from a heap of them already !
Just a “B T W” , when you purchase a new raw water pump from a Yanmar Parts Dealer, how long has that pump been sitting on the shelf already ? Do they have a shelf life if so how do you as an end user determine that ?
Your approach is very unusual. Most people carry a spare impeller, not a spare pump. It’s cheaper and easier and quicker to swap the impeller. The impeller is the part that breaks or wears out most often.
An impeller deteriorates just sitting in a pump because it is constantly deformed. One in use at least gets the chance to spread the worst deformation between blades. Also, the rubber can start to stick to the housing after a while and then blades can break off on the next start up. been there, done that. And of course, there could be a chemical reaction with the lubricant after a while. In normal use the lube washes off so it’s just pumping salt water.
“according to the internet”, Yanmar impellers are made by Johnson. I don’t know how to identify the material; maybe someone else does. But the easiest way is to buy a new impeller where you do know the material.
As for shelf life, the following documentation says to remove impellers for long term storage.
Jabsco makes both neoprene and nitrile.
Neoprene, or nitrile rubber, is a synthetic compound designed to resist chemicals, and to retain shape in a widely varying change of temperatures.
(The product is used for many purposes, fan belts, wet suits, diapragms in medical systems, etc)
Much of the “lore” about the treatment or storage of impellers relates back to the days of the old rubber impellers, which would rot, distort and tear. Nitrile does not distort or rot, but does sometimes tear, however, this is usually a sign of a deeper problem ithin the water pump.
All manufacturers now use the nitrile material (They didn’t tell us; we just discovered it when the price trebled!)
Consequently, for storage purposes, you actually need to lube the chamber, not the impeller, to prevent rust. I would be inclined to use teflon plumbers’ grease for this.
Just to throw our 2 cents into this discussion: Iduna’s Sabb engine has a diaphragm pump for it’s cooling water. We have spare diaphragms but I don’t think they wear out very often.
Thank You, again, John and Norris for your replies and further information, I find this info v helpful .
When I am at sea I stow my tools away and focus on sailing and navigating, so they really are not available to do mechanical repairs like remove and replace a raw water pump impeller.
Most of my sailing has been single handed, and I have found “Murphy’s Law” to be alive and well, onboard my boat.
Thus I conclude that when I have a ready to go spare pump, or other spare part the existing ones won’t break, sort of an insurance policy for me, but if it does break, my down time is minutes not hours.
Still on the subject of impeller life when stored in the pump, I am v curious as to how the engine manufacturers assemble the pumps. My Yanmar was purchased in 1986 and sat on the shop floor until 1996 (10 years) before installing it in my BCC.
That pump lasted another 6 years and 1800 engine hours before a new impeller was needed . I imagine that quite a few newly manufactured engines sit in storage for long periods before they get installed and used in service, and I haven’t read or heard of installers having impeller problems, just out of the box be it a new box or an old box .
John’s advice to check with plumbing shops is my next quest to find the Teflon Based Waterproof grease. O M G my wife just found this link, that I will try to follow up on : SG Tooling Pte Ltd | SG Tooling