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Water in lower unit after changing water pump BF50

G

greyg8r

New member
Hello,

I changed the water pump 8 months ago and have used the engine approximately monthly during that time. The water out of the telltale was getting weak so I checked the impeller and it had sheared off the vanes (without running dry).

Bought a new water pump and installed it and it pumps water great, but there is oil on the surface of the tub that I run it in and water is getting into lower unit.

What is most likely cause?

Thanks in advance.

Richard
 
Factory impeller or after market.----Motor needs a seal kit to keep water out.----Seals do wear after millions of turns of the shafts.
 
It was a factory impeller from a local dealer but it was dusty and I got the feeling it had been sitting around awhile. What seal kit?
 
There are numerous seals and O-rings on the shafts to keep oil in and water out.----Your dealer can order the kit or put the parts together so you have everything you need.
 
You don't say what year or if it's a BFA or BFD model so I just randomly selected the 2006 BFD as an example.

I agree with you that the impeller you initially purchased was likely old and brittle.

I included the link below because boats.net sells genuine Honda parts
for much lower prices than the dealers. The link is of the entire pump kit rather than just the impeller and includes everything you will need to completely RENEW your pump. Putting a new impeller in a worn liner and deformed or damaged housing will NOT give you 100% pump efficiency.

https://www.boats.net/catalog/honda...-lrta-2006/impeller-pump-kit-water-hose-joint

Racerone is probably correct about your gear case seals leaking but you might also get some light oiling of the tank water from the exhaust. Especially when the engine is cold.

Also, water is pumped through the exhaust manifold and then into the extension case. So seeing water exiting the case could be normal.
 
Thanks racerone and jgmo.

Update: I installed the water pump without installing the SEAL, WATER (17X30X7) 91251-ZV5-003 that separates the water pump from the lower unit. This has made a big difference, but the lower unit is still a little milky. Possibly, there is still water in the LU that is difficult to remove. But, I don't know if I installed the two seals correctly. I installed them so that the "open" sides meet. Is this correct? Thanks
 
It's my opinion that the lower of the two seals, the one utilized to keep oil from exiting the case, should be installed so that the "open" or "hollow" portion faces the case.

I think that, technically, the other seal should have the "cup" or hollow portion facing up.

This would mean that "my way" is exactly opposite to how you described that you installed them.

How critical is it to get them in properly??...I don't really know. The pressures involved are very low as is the vacuum that the lower one has to resist. So, it's conceivable that they could keep the unit sealed even if incorrectly positioned.

But, when dealing with the gear case and leaking, there are five other seals that have to be considered in addition to the mainshaft seal:

The shift shaft seal
The prop shaft seal
The prop shaft holder seal
And the drain and fill plug seals.

Any one or all can leak.
And, each one, excepting the top mainshaft seal must hold a slight vacuum during the gear case cool down. If not, water could enter the case even if oil doesn't leak out.

That's why it's important that, if you do the work, you need to be able to test that the unit is actually sealed. This typically only requires that you have a hand pump type vacuum pump and a modified fill/drain screw or equivalent to act as a pressure test port adapter. This would be a minimum. Of course, having an air compressor and low pressure regulator is helpful in pressurizing the unit. It's much easier than using the hand vac pump even though it will do the job.

This is the ONLY way to be absolutely sure that you "got it" after replacing seals. It's also the best way to determine which seal or seals are the cause of the problem.
 
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Most of the time, they go back to back like Jimmy says....however, these particular seals in the 50, both go the same way....the smooth side will be up as you put them in. The open sides go down.

Mike
 
Thanks Jimmy and Mike. I put the seals in as Jimmy described (and I saw some other online pics that were oriented the same way), tried it out and there was minimal milky appearance which I think is from the residual water. But, I am going to drop the lower unit and re-install them as Mike described.

I didn't (haven't) pressure tested the lower unit because it was fine before I replaced the water pump so the only logical leaks would be from the two water seals, the o-ring or the screw gaskets. If it gets milky after I reinstall the seals, I will pressure test it then.

Thanks again Guys! This 2000 Honda BF50 has had its share of things wrong with it but it is in good shape now and it was cheap.

Richard
 
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