Where do they find those guys with the clean fingernails? You’ve seen them; they always show up in the technical manuals. And why are their clothes so fresh? And where is the blood? I’ve never seen these people around any boats. Maybe that’s the answer to my questions: They aren’t around any boats.
Consider the photo of a guy gracefully removing the impeller to a raw-water pump while the engine is sitting on a bench. The manual always says something like, Remove the old impeller and put in a new one. Sure. That’s like saying, Just have a baby today. To a guy.
The mere act of setting up the job on my old Perkins 6-354 diesel was carnage. First I sprained my wrist when I reached down into the bilge to close the through-hull valve. Then I shredded my hands on the hose clamps holding all those hoses that had to be removed to even see the pump. Then I got soaked as water gushed all over the place, no matter what I’d done to contain it. Then I had to lie on my side beside the engine on a bountiful assortment of nuts and bolts and pipes and tubes and other objects.
There is some method to the madness here because lying on my side meant I only had one arm and hand free. Obviously, they planned it this way because there was hardly room to get more than a few fingers of one hand into the space where the pump lived.
No problem. There’s a lot you can do with three fingers. You can drop screwdrivers, drop screwdrivers and drop screwdrivers. This is actually a good thing because screwdrivers got me in trouble. The real problems began when I was finally able to hold the screwdriver long enough to start working on those tiny bolts with round heads and straight slots. They held the water pump cover plate in place, which had to come off to get to the impeller. Holding screwdrivers with only three fingers, when prone on my side only a few inches away, meant that I usually rounded out the slots. Occasionally I would get a few bolts loose so that I could drop them in the bilge with the screwdrivers.
But this left the faceplate still on the pump, meaning it was time to get those tiny locking pliers for the rounded-off slots. When I managed to break off the entire bolt head with the pliers, it was time to use a miniature drill. The only person I’ve seen with a drill that small is my dentist. If I could afford him, I wouldn’t be doing this job myself in the first place.
If I did get all the screws loose, all I had to do was pull out the impeller, right? That’s what the book says. And there are some handy tools for that. These tools do work — the manual shows them working in the pretty pictures. But these pictures usually just show a water pump and the impeller-pulling tool, along with those bloodless hands with clean fingernails. All of this is about as realistic as pictures showing you how to change your car’s spark plugs without opening the hood.
You have to get the impeller puller in place in front of the pump. But my old Perkins had a few things in front of, behind, beside, over and under the pump. They included an intercooler, lube oil cooler, transmission oil cooler, air filter, dipstick, oil pan, upside-down oil filter, lube oil hoses, oil-sending unit and assorted fuel lines.
For years, I refused to buy one of these tools because I figured it would take half a day just to get it into the space, if I could at all. But the pretty pictures in the books continuously beckoned. In sheer desperation, I finally investigated. I spent around 30 minutes on my side beside my Perkins (after spending about 30 minutes folding my body into position to fit into the space), holding a miniature tape measure in my three fingers so that I could take measurements. I couldn’t see the numbers on the tape measure because I couldn’t get my face in there. Even if I could get my face in there, my bifocals were on the bottom of my eyeglass lenses, not the top. Needless to say, I couldn’t extend the tape measure with my three fingers without dropping it into the bilge.
I concluded that I didn’t have a clue as to whether that impeller puller would fit into, much less work in, that space. But seeing the bloodstains from the last job, I was sure as hell going to try it, so I bought one.
After wedging back into the war zone and fiddling for 15 more minutes, I got the tool into place, and it worked. The impeller slid out like a … well, never mind. But they don’t make a tool for getting the impeller back in, at least not one that I’ve seen. This isn’t an easy job. The books say to grip it firmly and, with a rotating motion in the same direction that the pump shaft turns, slide it in, knuckles be jammed and damned.
I asked an “official” technician about all this, and he answered: Oh, just remove the entire assembly from the engine. I won’t even begin to describe what you had to do in order to remove the entire assembly from the engine. Or what you had to remove from that engine to get to the entire assembly so that you could remove it. Things really got exciting when I had to do this in a hurry, when the engine stopped pumping while we were in an inlet with a squall line coming.
If you’re one of the lucky people who has a raw-water pump with an impeller that’s easy to change, count your blessings — and your fingers. And I’ve joined you. A few years ago, I got a new 200-hp Yanmar that seems to be remarkably lacking in homicidal intent. The pump is easy to remove and put on a bench, where the impeller is easy to remove.
But now I’m selling the boat … and I’m wondering why.
I think I know. If you have a boat you can’t complain about, nobody believes you have one.
* * *
Just so you can complain a little less, here are some things I’ve learned over the years about changing an impeller. These won’t keep you completely out of trouble, but they’ll keep you out of the deepest of it … maybe.
1. Disconnect the engine’s battery and close the engine through-hulls.
2. Many people pry out old impellers with two flat-blade screwdrivers. Some of the best mechanics do this, but the technique can easily damage the pump lip, against which the cover plate is supposed to snugly seal. This not only can result in leaks, but it also can create deformities inside the pump, which can wear out the impeller much faster than normal. I’ve also found that water-pump pliers seldom work well and can mar the inner pump surface. An impeller-pulling tool is worth the money.
3. It’s best to change your impeller at least once a year, whether it seems to need it or not. If the blades break off, they will be washed against or into the tubes downstream, which can obstruct water flow and impair cooling.
4. Once the impeller is removed, check inside the pump for signs of corrosion, electrolysis and wear. Have a spare wear plate on hand in case the old one is significantly worn and has to be replaced. This is the little plate that forms a “hump” on the inside wall of the pump, against which the blades flex. Sometimes these are easily replaced by just removing a screw. (They also can be part of the pump body, in which case you may need a new pump.) Compare the size of the pump plate against the new one to see if the old one is badly worn. Some pumps have wear plates in the back end that should be examined for scoring.
5. I prefer to put a tiny amount of water-pump grease on each side of the cover plate gasket. (The gasket should be a part of the impeller kit.) This helps to hold the gasket in place as I’m fitting the cover plate, and it helps to seal it. If air leaks in around this gasket, the pump may not work properly. When I have to do this job again, the grease is easier to clean off than silicone sealants.
6. Before you put the new impeller into the pump, spread the lubricant liberally around the walls inside the pump and on the shaft. This will help you get the impeller into the pump and provide lubrication when the pump picks up water after you’ve resealed it and started the engine. Many people say using grease in the pump body can damage the impeller. They say to use glycerin or dishwashing soap. I’ve never had water-pump grease damage an impeller, but that’s what “many” say. The grease on the shaft will help prevent the impeller from seizing when it’s time to remove it.
7. When you put the new impeller into the pump, don’t put lubricant on the impeller, and do clean all grease thoroughly from your hands. This will help you grip the impeller, depress the blades and turn it into the pump. Use a clean rag to help you hold the impeller if it has gotten greasy.
8. Apply an anti-seizing product such as Permatex Anti-Seize 133K on the cover plate screw threads before reassembly. This should make them easier to remove next time.
9. If you can’t depress the blades sufficiently with your hands to get them into the pump, try this. Get a quality hose clamp that doesn’t have perforations and has rounded edges to avoid cutting the blades. Fit it around the impeller and begin tightening. You’ll have to find an area on the impeller that’s close enough to its center to depress the blades sufficiently, yet far enough from the middle so that the impeller can be pushed into the pump and onto the shaft. As you tighten, make sure the blades deflect in the correct direction. Don’t overtighten, and take care not to damage the blades. They will be extended enough so that you’ll still have to push, but it should be easier. When the impeller is mated with the shaft and won’t pop out, loosen the hose clamp and slide it off the impeller. Sometimes tapping the impeller the rest of the way in with a rubber mallet helps.
10. Before starting the engine, open the raw-water through-hull valves that you closed prior to the job. If the engine or pump is below the waterline (and there is no higher loop between the through-hull and the pump), let it sit for a few minutes so that seawater will find its way to the pump. This will help provide a well-lubed startup and reduce the chances of damaging the blades from dry running.
This article originally appeared in the March 2017 issue.