1999 Johnson 115 V4 Lower Unit Seal Replacement

[Captain Jeff]

Hello All,

The dreaded milky gear oil came out when I changed the lower unit oil on my 1999 115. I have been changing the oil twice a year. When I did the water pump 2 years ago the shift rod seal looked a little questionable but there is no telling exactly where it is leaking from. I plan on getting the entire lower unit seal kit as well as doing a complete water pump rebuild while I have everything apart.

My question: is this going to be a major project doing the prop shaft seal and o ring on the bearing carrier? Will I have to align and shim the gears / pinion gear or what? Also would it be worthwhile to replace the main bearings while I am at it?

Thanks in advance

 

[ob]

Re: 1999 Johnson 115 V4 Lower Unit Seal Replacement

I'd first make sure that your leak is not simply the fill and vent screw seal washers that are the culprit.As for the bearing carrier removal,it won't require any shimming or alignment of lower unit gears.

 

[Captain Jeff]

Re: 1999 Johnson 115 V4 Lower Unit Seal Replacement

Thanks ob. The fill and vent screw washers look good and I keep them very tight but I will have another look at them. How can I check further? I have heard of people pressurizing the lower unit with compressed air?

 

[ob]

Re: 1999 Johnson 115 V4 Lower Unit Seal Replacement

I know some guys that have used a common bicycle pump with a stem fitting with schrader valve adapted to the vent screw hole and pressured the lower unit up with the lower unit submerged in a tub.Drain the gear oil first.The water line needs to be over the vent hole level.Also don't want to over pressure during the test.10 psi is sufficient.This test will only expose a leaky drain plug seal or propshaft carrier seals and/or "o" ring where the carrier seats to the lower unit housing via bubbles rising from vat.Otherwise ,if it won't retain 10 psi it may indicate an internal leak of the shift rod or propshaft seals.The right way to have it done is to perform a pressure and vacuum test however.

How did you determine that the shift rod seal "o" rings was borderline?Did you remove the shift rod flange on last waterpump service?If so,was the shift rod flange cover gasket disturbed?Is there any sign of emulsified gear oil in or around the area of the propshaft seals with the prop removed? Many times if one of the propshaft seals or carrier o rings are bad and allow water intrusion when submerged,they will also weep gear oil when not in use.

 

[mankato]

Re: 1999 Johnson 115 V4 Lower Unit Seal Replacement

I bought a MityVac brand vacuum/pressure combo hand pump off Ebay when I was in the market for a replacement lower unit for my Evinrude 120 V-4. There's one on Ebay right now that's dirt cheap - the description is "Mityvac Silverline Vac/Pressure Combo Pump and Cooling". When my gearcase is empty, I can vacuum test it and then when I've filled it with lube, I can pressure test it (10psi). I just use the fitting & line from my Lubrimatic filler pump. You leave the pump pressurized overnight to make sure that you don't have even the slightest slow leaking seal. Now I pressure test my lower unit about every third or fourth time I use the boat, since it only takes a few minutes to check it. Then I can also use it for applying vacuum to vacuum lines for diagnosing other engine problems on my car, trucks, etc.

 

[Captain Jeff]

Re: 1999 Johnson 115 V4 Lower Unit Seal Replacement

Thanks guys. The shift rod seemed like it moved laterally slightly and the area seemed a little "crusty" but that was probably the trapped algae particles. I did not remove the shift rod flange cover and the gasket looks good from the outside. No sign of oil near the prop shaft seals.

The pressure / vacuum test sounds like a plan.

 

[mudd_mickey]

Re: 1999 Johnson 115 V4 Lower Unit Seal Replacement

I wouldn't call it an easy project but I also wouldn't pay someone to do it. There are a lot of parts in there so make sure you have a repair manual, take your time, and be patient. You'll likely need a bearing/crank puller to get the lower bearing carrier out and if it's really stuck you might need some heat as in a torch to heat up the outside of the lower unit. You'll also need 10" to 15" bolts to attach to the bearing and work with your puller. I'd suggest either buying a nice puller or renting one but take your lower unit with you so you can match a puller up to it. Not all pullers are the same and it's this little crap that makes these jobs a pain in the @$$.