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2000 BF40AY: changing impeller and servicing lower unit for first time...

T

texasAUtiger

Member
in a recent thread I discussed successfully replacing the fuel pump. Thanks for the help.

When it rains, it pours so as soon as I get back on the lake to test the new fuel pump, I get an overheat alarm. I get back home and investigate for clogs, I find nothing. No tell tale stream. I check the water intake down by the prop and behind the little screens is a small handful of rubber bits. So, despite the dealer having put a new impeller on just 19-20 months ago, it seems my impeller is shot. I could take it back to the dealer, but I want to be more self-sufficient. Hopefully with you guys helping me, I can do this myself.

Looking here:

https://www.boats.net/catalog/honda...0/bf40ay-lra-vin-bays-3200001-to-bays-3209999

and more specifically, here:

https://www.boats.net/catalog/honda...00001-to-bays-3209999/water-pump-impeller-kit

I'll get the parts listed there.

Is there anything else I need to grab in order to properly service the lower unit while it's off? Any other routine maintenance to do while the lower unit is off? Anything in particular to be sure to do or not do in order not to screw something up?

Thanks!
 
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It's straight forward. I have a 115 but I imagine the process is the same. Get the kit with the impeller, woodruff key and seals. You probably do not need a new pump housing unless you see tons of wear/scarring inside the pump housing, just look at the metal.

Make sure you put the impeller back in the same "pattern" as it came out - imagine a starfish, the legs all face a certain direction. I use the shaft to help guide the impeller back in the housing. Use grease on all mating surfaces to seal the lower unit back to the main body when you attach it. I had a speedo pickup tube that is zip tied to the lower unit - cut the zip tie. Get a new zip tie.

Make sure you pull it straight out, do not bend, do not twist. The shaft to the lower unit will have an alignment key - flat surface - that mates back together. You have to try to rotate it so you should not be out of alignment, but pay attention either way.

If your in tight quarters to get the bolts off the lower unit, do yourself a favor and get a wratcheting wrench (not a socket). Mine are 10mm.

Also never discount the power of weed trimmer line passed in the tell tale outlet to clear clogs... you will be suprised. Common issue on Hondas.
 
Do I need to replace any of the seals/O-rings from the shift rod when I do this? I didn't know if pulling things apart to get to the impeller would compromise any seals, etc. anywhere else other than around the water pump.

I want to make sure I order everything the I might need the first time.
 
Normal routine is just the gasket on the impeller housing itself - it comes with the kit you are buying. There are other seals but unless you see water in your gear oil you are OK.

Check your lower unit gear oil after a few trips. No cloudy oil = no water in, and you are OK.
 
If your impeller which is less than 2 years old is shot, you need to replace the Housing, Seals and Impeller. Then you will have a worry free mind on the topic. It isn't much money for the housing. Here is a video, its a yamaha, but its a universal process for the most part.

https://youtu.be/IqNk4P94wOs
 
eneusiis said:
If your impeller which is less than 2 years old is shot, you need to replace the Housing, Seals and Impeller. Then you will have a worry free mind on the topic. It isn't much money for the housing. Here is a video, its a yamaha, but its a universal process for the most part.

https://youtu.be/IqNk4P94wOs
Click to expand...

Thank you, I will add those to my parts order.

When servicing the lower unit are there any parts that need to be changed out like seals or screws or anything?
 
texasAUtiger said:
Thank you, I will add those to my parts order.

When servicing the lower unit are there any parts that need to be changed out like seals or screws or anything?
Click to expand...

I always carry extra lower unit nylon washers. I change them on the fill and breather plug holes each season to ensure they are not my weak point. They are cheap.

Other things to check on the lower unit are:

- Pull your prop off each season at minimum to inspect for fishing line behind the prop
- The minute you find water in your lower unit oil, locate the leak and change the seal. It will be one of the few areas such as the fill/breather hole nylon washers, prop seal, impeller housing seal on the prop shaft or the seal on the shift shaft.

That is the jist of it.
 
My parts arrived today so I got started on changing the impeller, my first time doing it.

I got the bolt under the trim tab and 3 of the 4 side bolts off the lower unit with no problem. But one of them is stuck. I've used a hammer to gently tap and even went to hitting pretty good (medium). Sprayed it down with WD40. Doesn't budge. I could get a cheater bar, but I'm afraid forcing it any more than I have will break it.

Ideas on what I should try? I can get some penetrating oil and let it sit on it overnight. If I use heat, I assume I just apply it to the head of the bolt. Is it okay to do so? I don't want to damage any of the surrounding lower unit.

Thanks for your suggestions.
 
A little heat did the trick!

LOL, it took me 45 minutes to get that one bolt off and maybe 30 to do the entire rest of the project! I replaced the impeller, liner, housing, seals, everything the manual recommended. It was simple. I encourage others to give it a try.

It took a little fidgeting to get the lower unit lined up and back on (working by myself, so you can't see and the lower unit is a little awkward to handle), but it's on. I ran out of daylight so I'll reattach the shift rod and tighten everything up tomorrow. I'm a little hesitant to put her back on the muffs, but this time I'll tape up the underside water intake and use muffs plus a small barrel of water.

Fingers crossed!
 
I tightened everything back up this morning and used anti-seize lubricant on the bolts to make the job easier next time. Taped the bottom water inlet and put muffs on the side. Fired her up and the tell tale was very strong. Woo hoo!

I did have to play with adjusting the nut on the shift rod to get it to shift smoothly without grinding, but no big deal. I took it to the lake this evening to test it under a load and everything worked just fine. I thought the telltale weakened a little so while on the water I detached the little black rubber hose that goes from the engine to the where water exits the tell tale and revved the motor to blow out any debris. Put those back on and the tell tale was consistently strong.

It's nice for things to work out. ;-)

I'll change he engine oil and lower unit gear oil later this week.

Again, anyone who is thinking of tackling this yourself, do it. Saves a lot of time waiting on it to be serviced at a shop as well as some money.

Thanks again for the help!
 
Nice job, pretty easy stuff if you put your mind to it. Dangar Marine on Youtube has a ton of videos on the BF40. I bought a 1998 BF40 a few years ago, and for peace of mind, I did a top to bottom rebuild of the engine to ensure it was tip top. I used his videos like a bible. If you search on here for BF40 or by my username "eneusiis" you will find many posts for potential future reference for yourself.

Good luck!
 
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