Water in lower unit

[cam1399]

I have a Mercury black max 150. I’m getting water in my lower unit. I have changed impeller gaskets and prop seal. Where else can be leaking into lower unit? Thanks

 

[Chris1956]

Mine leaked twice thru the shift rod seal. The obvious other place is the driveshaft seal in the waterpump base.

If you have one of those gearlube pumps, you can use the fitting and plastic tube to test the gearcase for leaks. Drop the gearcase, drain the gear lube, screw in the tube and use a bicycle pump to pressurize the gearcase. Use some soapy water to find the leak, if it is not obvious.

The shift rod seal screws into the gearcase. A punch can unscrew it. I made a spanner out of a 3/4" black pipe coupler to tighten the replacement seal.

If the driveshaft seal is leaking, buy a new waterpump base and seal, and install it with the correct oring. Clean the driveshaft with sandpaper before installing the new water pump base.

 

[Chris1956]

Here is the seal for the shift shaft

77631A2 Shift Shaft Bushing Assembly - Mercury Marine | Crowley Marine

Find Shift Shaft Bushing Assembly - 77631A2 here. Offering discount prices on OEM Mercury Marine parts for over 50 years.

www.crowleymarine.com

 

[Scott Danforth]

pick one.

• crack in case
• bearing carrier to case seals
• shift shaft seal
• pinion seals
• prop shaft seals

do a pressure test to find out

 

[Texasmark]

pick one.

• crack in case
• bearing carrier to case seals
• shift shaft seal
• pinion seals
• prop shaft seals

do a pressure test to find out

Plus seals on screws removed when changing LU lube as a potential culprit. If soapy water doesn't show anything, get a tub of water and with the LU pressurized as stated..like 10 PSI, submerge the LU and put it in different positions while submerged. Some seals are bi-directional....lip one way to keep water out and lip the other way to keep oil in......prop shaft for sure has this pair.

 

[Chris1956]

To add to what Mark said, If you cannot find the leak, rotate the driveshaft and shift shaft with the pressurized gearcase under water. If the driveshaft bearing is worn or the shift shaft bushing is worn, they can leak as they are turned.