Lower Unit seals failing repeatedly

[laxandpb4life]

My 250 Pro Xs has blown three sets of lower unit seals in the last 5 weeks. Any Idea why this could be happening repeatedly? The first two times it was the prop shaft seal, looks like it was the shifting seal this time.

 

[MH Hawker]

Re: Lower Unit seals failing repeatedly

Internal Pressure

 

[Faztbullet]

Re: Lower Unit seals failing repeatedly

Use the HI-Po oil from Merc or others as cheap 80/90 W will aerate and expand. Had several Mercruisers with Gen 2 units do this last year(shift seal) and all had Autozone 80/90W installed by owners...

 

[Dukedog]

Re: Lower Unit seals failing repeatedly

Ya gotta run it low. Drain a coupla ounces out after ya fill it up..................There is a "catch can" type of deal being made that works if your interested. Think its offered (or use ta be) by Lakeland Marine called a "vent kit". Really more of an "expansion chamber" than vent! Might check with Diamond on this too...........

Just somethin' else ya might be interested in. More invasive but cures tha problems pretty much for good. Believe Wayne Taylor makes some billet parts for tha SM. One replaces tha plastic single O-ring driveshaft seal under tha water pump with a four O-ring billet unit and another billet piece that replaces tha shift shaft seal. Heard nothin' but good 'bout these parts..........But ya still gotta run it a tad low on gear oil.

 

[Texasmark]

Re: Lower Unit seals failing repeatedly

Use the HI-Po oil from Merc or others as cheap 80/90 W will aerate and expand. Had several Mercruisers with Gen 2 units do this last year(shift seal) and all had Autozone 80/90W installed by owners...

So that's the why behind don't use regular gear grease. Thanks. I use the QK high perf myself but threads have come and gone where some suggested the only oil we had available 50 years ago. Course 50 years ago you didn't have 300 hp outboards either. Grin

Mark

 

[Dukedog]

Re: Lower Unit seals failing repeatedly

Don't know much 'bout tha Mercruisers stuff like Fb but tha with tha others its tha sporty that's givin' tha problem. Its mainly cause of being "surfaced" per sa as opposed to tha norm. It builds too much heat with tha loads being put on 'em. They do it with ANY gear oil....

 

[Texasmark]

Re: Lower Unit seals failing repeatedly

I think I recall reading about "low foaming" on marine gear oil containers years ago. I guess they have additives that keep it from puffing up like meringue on a lemon pie.

Mark