Honda BF50A lower unit

Albertfishing

Recruit
Joined
Nov 28, 2015
Messages
4
Made a transmission oil change today and found the old oil became milky, also a sign of overheat at the upper part of the lower unit. What is the problem? Thanks
 

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hondam

Petty Officer 1st Class
Joined
Nov 21, 2013
Messages
213
The oil is milky because a lower unit seal is leaking. The shift rod boot is usually the problem with those, they need to be changed periodically and is very easy to change.

Some degree of that discoloring is normal, The midsection gets warm running down the lake and the mineral deposits in the water have a tendency to build up on the Honda paint

If it is overheating you may have melted the water pump housingand/or impeller most likely because you didnt cover the secondary water intake when running on the flush muffs. There is a plastic screen on the bottom side of the cavitation plate above the prop that you need to cover with a piece of duct tape when running on the muffs because if you dont all the water being pushed in the primary intake will just run out the secondary intake without actually entering the pump. When you melt the upper housing 9 times out of 10 you partially melt the lower housing that holds the drive shaft seals. I would replace the housing and seals too as well while your at it if its the case.

These are both very common issues i see with these motors, the are no big deal to fix as soon as your aware of it.
 
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Albertfishing

Recruit
Joined
Nov 28, 2015
Messages
4
Thank you hondam for your prompt response. I will be looking at the Shop Manual in order to better understand the details in your reply.

Early this spring, the engine hit a rock pile and the stainless prop was badly damaged. Does this have any thing to do with problems mentioned above?
 

hondam

Petty Officer 1st Class
Joined
Nov 21, 2013
Messages
213
Depends... Did you replace it or have it fixed immediately? If the lower unit survived the initial impact continuing to use a damaged prop especially a SS one can ruin a lower unit. If you hit it hard enough you could have bent the prop shaft too so spin the prop and make sure it doesnt look bent. But hitting something on its own usually do not cause the issues you have described its neglecting the repair that could potentially cause an issue.

Also there is a big difference between how Aluminum and SS get damaged when they are hit. Aluminum tears up fast, gets mangles and often tears off chunks. SS blades are much thinner and stronger then the aluminum and tend to bend way before any parts of the prop get tore off. This bending does not always happen at the tip so with the naked eye the prop may just look like it has some minor dings and a slight bend to the tip but when the prop shop puts the prop in the tool they use to form the blades called a pitch block it could be WAY off. So its important to have a SS prop checked after any significant impact reguardless of what it looks like, most prop shops that i know wont charge for just checking it.
 

Albertfishing

Recruit
Joined
Nov 28, 2015
Messages
4
Thanks hondam again!

Yes I replaced the bad prop right away. The max. speed of my boat didn't really drop after so I would assume that the prop shaft is still in good shape.

Now the lower unit is off...

There is no obvious sign of melt nor damage / distorted part found. but I will order a water pump kit to replace anyway.

I will also replace the shift rod boot as handam suggested. Is this shift rod boot also call "Grommet, shift rod" as part #12 in the link below?

http://www.iboats.com/Impeller-Housing/dm/cart_id.359872151--session_id.058116692--view_id.1326781

Surprised to find the end nipple was missing( part #17 in http://www.iboats.com/Extension-Case/dm/cart_id.359872151--session_id.104004769--view_id.1326784). What is the function of this end nipple? Just wonder if I need to buy a new one and put on.
 
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