Impellers

[Tireless]

I saw a discussion on the Trent Severn Waterway Forum, here in Ontario, where someone stated that you must be sure to install your impeller properly. They went on to say that impellers do NOT self correct if they are put into the housing with the blades in the wrong direction. The author advised that if your marine tech tells you they do self correct, it's time to find a new tech.

I have always been told that impellers do self correct and I have been advised this by marine tech's over the years.

What are your views on this and I am interested to hear what forum members have to say about it.

It is the proper time for a discussion like this, as you all known, many of us will be replacing our impellers in the next short while.

Greg

[Viper]

I like installing them in the correct position to begin with but even OEMs tell you that it doesn't matter. On that note, I've never ever pulled one out that was facing the wrong way and I've replaced a lot of them. So I guess that means every one that installed them originally set them in the right direction to begin with? Probably not. Nothing wrong with going the extra mile and setting it in the right direction at the beginning.

[g36]

I always worried about putting them in the right direction to until I did it wrong several years ago on one engine of my trojan . I had just got it so I had someone crank it over from the fly bridge and then I realized my mistake. Opening it up they had already flipped over to the correct rotation, ever since I still try to do it the right way but figured if I did it wrong they would self correct. If in doubt try it for yourself. I bet you'll see they flip over the right way too.

[tomschauer]

If you take a complete new pump housing and impeller, from an inboard or stern drive, on your bench, install the new impeller with the vanes installed in the opposite rotation, one full revolution and they are in the correct position. Maybe if the impeller is old stock and somewhat brittle it may be a problem, otherwise no issue.

[Cooler]

Although it is possible they will self correct, I had an experience on a Volvo where I installed backwards, and the impeller completely failed right away. There was literally almost nothing left to the vanes on the cam, and a bunch of rubber clogging up the screens going into the cooling line. Engine overheated on first cruise from dock. Since then, I make sure they go in the same way they came out. er

[Viper]

Cooler, that was most likely a bad or old impeller, or it wasn't lubricated enough before installation. A bad pump cam will cause the same failure.

[dskasner]

Placing the impeller with the fins pointing in the wrong direction will self correct. If you find one that has failed it was because the impeller was beyond its service limit. I.E. old impeller. Rubber over time will dry out and fail. Buy only fresh impellers. Do not store them for years expecting them to be ok when you decide to put them in. Be carefull of cheap internet or garage sale impellers that are inexpensive. You buy thinking they are good. Nice packaging, must be fresh, and they are far from it. Those are the ones that fail very quickly after install. The rubber fins compress just about to the hub they are attached to. Alot of flexing per revolution. Lube Lube Lube during installation. I use a silicone based product. Slides in real easy. Leave key out. Rotate a few degress to align keyway after fully inserting. Install key. Fins will flop into correct position.

Sit down
Drink Beer

[Midnightsun]

It is always a good idea to keep spare impellers on board. Remove the impeller from the box and smear it down with 100% silicone grease. https://www.ebay.ca/itm/Silicone-Grease ... 1674699592 This will stop the drying out of rubber and extend the life substantially. No question it is still as good as new 5 years down the road when you need it. Also make sure it is put back in the box and kept away from sunlight. A dark temperature controlled environment such as a cubby hole in the cabin is a great place to store them.

I also use this on all o-rings such as fuel filler, sea strainer, water fill. Just really great stuff for rubber in general.

[bud37]

I try to change impellers immediately before they will be used, never put new ones in then leave them unused for a long time in the pump. The other is to rotate the pump impeller during the lay up when you can ,it generalizes the fin set....at least rotate the impeller a week or so before spring start up, that way it won't be stuck....lot's of dish soap on instal, even if you don't get it in just right they will flip and you can see the soap bubbles out the exhaust.

Some folk used to remove their impellers at lay up then put them back in the spring or when the boat went back in. I only ever did that once.

I agree about trying to buy new fresh stock if at all possible.

[Viper]

Source of the post..... rotate the pump impeller during the lay up.......

I do that all the time throughout winter bud. I bump the motors over periodically including the generator. I don't just do that for the impellers though, I don't like any moving part of an engine remaining in the same spot for long.

Source of the post....Some folk used to remove their impellers at lay up then put them back in the spring or when the boat went back in......

That used to be a common practice but more and more techs determined that you do more damage removing and installing than just leaving them in. Given that you should be replacing them every couple of years anyway to be safe, what's the point of removing them just for lay up. Some owners still do it though. That's like customers asking me to check their impellers and replace if needed. My reply is always...I don't check impellers, I replace them. If I'm going to get in there and open the pump, I'm replacing the impeller! Same goes for spark plugs, what's the point of paying the labour to have someone remove and install the same plug! I get asked all the time to just check them though....not happening.