Checking/changing impeller BF75D

Hi, I about to do my first own service on my BF75D. When I look at the service schedule it says to "check" the impeller every year. Any idea how this should be checked? Is it open up the pump and actually looking at the impeller? What would you suggest I look for on the impeller?

Ones I open up the pump I have to replace the oring right?

Fact ----The impeller is a very important part , more important than most folks realize!!-----But it depends on the area you boat in, and temperature of the seawater.----Clean water or lots of sand such as on party sandbar !----If you can do the work yourself a new impeller every 2 years is cheap.------A water pressure gauge and a temperature gauge are also very good options and easy to install.----But you must know how to monitor these gauges.------Cold water is harder on a flexing rubber part than warm water.-----Operating a boat is not the same as pushing a button in a modern vehicle and roaring out of the garage !!

Right right, Im aware it is a critical part. I probably run about 100h every year, clean but a bit cold water. Is it stupid and cheap to change the impeller every three years and not do any deep inspection between this?

First, I wouldn't do this annually. Not unless you were putting a terrific amount of time on the motor every year. I think most of us could get away doing this every 3rd year - assuming we started with a new impeller. So replace the impeller when you get the motor so you know where you are at (unless purchased new), then service/have a look at 3 years. This would be on the safe side. I think some, putting a limited amount of hours on annually, might get away with 5 years. That's pushing it though - and ONLY if you know how old your impeller really is.

You would be looking for any apparent cracks in the black rubber material, or signs of unusual wear.

I would replace the o-ring.

I would use never seize on the bolts during reassembly.

I think replacing the thermostat at about the same time intervals is a good plan as well.

If you are going to pull the lower to check the pump you might as well replace it.... Never use antiseize bellow the water line... Perfect seal or water proof grease on the hardware.

Change the pump every two years... Unless you dragged the engine through the sand or mud....Then sooner.

If you pull the gearcase for "inspection" it makes no sense not to replace the impeller and oring. as Chris has already said.

I just want to add to this discussion that the REAL inspection occurs when you examine the metal cup that the impeller sits in and the plastic housing that the cup sits in. The impeller, the cup and the housing together are what comprise the water pump as a WHOLE.

What most owners don't realize is that the impeller and cup begin eating at each other and incurring wear the moment you first put the pump in service. As a result, you can never achieve a 100% pump repair by placing a new impeller into a used cup.
It's very much like putting new brake pads on a worn rotor on your car. The new pads will IMMEDIATELY wear into the shape of the old rotor. Your outboard water pump acts very much the same way and you need to keep that in mind when inspecting the cup. While it's perfectly reasonable that a new impeller can be expected to work fairly well in an old, SMOOTH cup, I wouldn't recommend it with a cup that has ridges or gouges in it.

Also to consider is the plastic housing that the cup sits in. The pump will tend to operate at a high temperature at startup prior to gaining it's fluid prime. This can take a toll on the plastic housing over time and cause it to distort. If the distortion is severe enough, the metal cup will no longer be held stationary in the housing as when new. This movement will increasingly get worse and ruin pump efficiency.

So, you see, there's more to "inspection" than just the impeller.
I also suggest that you look VERY CLOSELY at the drive key. I guarantee that you'll find wear there too.

For these reasons it is wise to consider the complete pump kit that is available as well as a new drive key if you see wear that makes you look twice.
As already said, the water pump is just too important to the outboard as well as your safety out there on the water.

Good luck

Won't disagree that if you're pulling it you might as well go ahead and do whatever the pump needs.

I think the bigger question might be how often it needs to be "removed for inspection". As mentioned a lot is going to depend on how much, where and how it's used. Every other season should cover most of us, but some may be able to double that.... Not that I'm going to recommend they do that. -Al

Ok so summing up. Open up the pump every two years, replace impeller and key from standard kit. If there is wear on the cup, replace it as well. Sounds about right?

rasmuss said:

Ok so summing up. Open up the pump every two years, replace impeller and key from standard kit. If there is wear on the cup, replace it as well. Sounds about right?

Click to expand...

Remove the lower every two years and replace the complete pump along with the thermostat and you will not have any issues. This is the way it is done for trouble free boating.

The complete pump housing and all is inexpensive.