TM Lower unit keeps blowing out the seal .

[wally 2]

I have a 2008 Pro XS 250 hp with a TM Lower Unit . I've had the lower unit seal come out three times . My first mechanic said I have a worn hub or a bad prop thats making vibration and caused it to work out . My hub was loose inside the prop so I replaced the strips on the hub and then she fit tight . Three short trips in the water it worked out again . Had to take it to a different mechanic . He checked out the shaft all the measurements said everything looks good . Said if it happens again it's probably because my exhaust . Its somewhat plugged going down through my lower unit causing pressure . Said he would have to take the head off to get at it . Well sure enough it worked right back out . To make sure my prop was ok I sent it to Mark . He called me said it's was good balance been blueprinted in the past. There shouldn't have been any vibration from it . Great service from Mark and my prop is on its way back in less than a week . Taking it in next week to the second mechanic thinks it is my exhaust . Has anyone else ever had this problem ?

[wally 2]

I have a 2008 Pro XS 250 hp with a TM Lower Unit . I've had the lower unit seal come out three times . My first mechanic said I have a worn hub or a bad prop thats making vibration and caused it to work out . My hub was loose inside the prop so I replaced the strips on the hub and then she fit tight . Three short trips in the water it worked out again . Had to take it to a different mechanic . He checked out the shaft all the measurements said everything looks good . Said if it happens again it's probably because my exhaust . Its somewhat plugged going down through my lower unit causing pressure . Said he would have to take the head off to get at it . Well sure enough it worked right back out . To make sure my prop was ok I sent it to Mark . He called me said it's was good balance been blueprinted in the past. There shouldn't have been any vibration from it . Great service from Mark and my prop is on its way back in less than a week . Taking it in next week to the second mechanic thinks it is my exhaust . Has anyone else ever had this problem ?

And I am sure I have the correct oil in the lower unit

[wally 2]

Serial number is 1B547643

[Bryanmc57]

Are you overfilling the lower when you change the fluid? I believe with the TM lowers you fill them until the oil just reaches the threads in the vent plug, then allow 1-2 ounces to drain out while putting the drain plug in.

[DewRonInc]

I used a billet carrier on output shaft, propshaft, it has been flawless

[DewRonInc]

U can pull lower and look, that don’t sound like the issue myself.. I use Mercury racing gear lube, different and very good lower lube

[lpugh]

I have a 2008 Pro XS 250 hp with a TM Lower Unit . I've had the lower unit seal come out three times . My first mechanic said I have a worn hub or a bad prop thats making vibration and caused it to work out . My hub was loose inside the prop so I replaced the strips on the hub and then she fit tight . Three short trips in the water it worked out again . Had to take it to a different mechanic . He checked out the shaft all the measurements said everything looks good . Said if it happens again it's probably because my exhaust . Its somewhat plugged going down through my lower unit causing pressure . Said he would have to take the head off to get at it . Well sure enough it worked right back out . To make sure my prop was ok I sent it to Mark . He called me said it's was good balance been blueprinted in the past. There shouldn't have been any vibration from it . Great service from Mark and my prop is on its way back in less than a week . Taking it in next week to the second mechanic thinks it is my exhaust . Has anyone else ever had this problem ?

When filling the lower unit and the oil just starts creep out the vent hole, stop filling and and wait for the excess to run out, Install the vent plug, remove the fill adaptor and let 2 oz run out before you put drain plug back in.
skipping this step will cause this issue due to lack of room for heat expansion,
I would highly recommend using mercury 85-90 racing gear lube.
Any water contamination in the gear lube will also cause this
I would not let either one of those 2 tech touch it again

[wally 2]

Thanks guys . I didn't know about the overfilling . I've never let 2oz back out of it . I've had the boat four years . I buy the Mercury high performance 90 buy the case and change the oil twice a year . Never had a problem till last fall . My second mechanic got ahold of Mercury and they are the ones that told him about the exhaust . They told him to make sure I am using the right oil . The Mercury high performance 90 like I am . And if it does it again it has to be my exhaust . I've called around to a few mechanic and they have never seen the exhaust be a problem before . I guess I have to trust what Mercury tell's my mechanic . And make sure it's not over filled . Really don't know what else to do .Was hoping to hear from some of the Mercury guys on here . Thanks

[JOE54]

well i wish i knew how many torquemaster gearcases i have repaired , seals must be loctited and oil level must be correct ,, and how many 3.0 engines i have clean idle relief passages in that were completely stopped up solid and ran without a seal failure for years , you get a written money back guarantee that cures it or walk off , early 3.0 engines had a cooling issue that did burn propshaft seals but not pxs or torquemaster engines good luck sir JOE

[wally 2]

Thank you very much Joe ! What type of loctite ?

[JOE54]

red 271 , the good stuff

[EuropeanAM]

Sounds like it's been over-filled to me.

[wally 2]

Thanks everyone I appreciate the advice ! Seals are getting loctited in . Mercury racing oil and she won't have to much oil in her . I make some long runs with her so hopefully she says together .

[DewRonInc]

The Mercury racing oil does not build the pressure, according to merc racing, like other lubes do. Designed for surfacing units that get hotter and then drop in water when u shut down. That will cause water intrusion, rapid cooling. That oil does help with that. I fill my sporty up to the threads, been good for me

[wally 2]

Thanks Dew I will be using it !

[EuropeanAM]

I used a billet carrier on output shaft, propshaft, it has been flawless

^^^^ This probably has more to do with your results than the lube does. Not knocking the Racing lube, but can't say I've seen any significant reduction in seal failures with it.

[lpugh]

^^^^ This probably has more to do with your results than the lube does. Not knocking the Racing lube, but can't say I've seen any significant reduction in seal failures with it.

I do think the racing lube runs a little cooler, I went from three lube changes a year to two, does not turn black as fast and does not have that burnt smell to it. Still evaluating though, I use it in all lower services now.

[blackboat]

red 271 , the good stuff

Joe, is that the same stuff Mercury labels "7" in a squeeze tube in the parts diagrams?

[DewRonInc]

^^^^ This probably has more to do with your results than the lube does. Not knocking the Racing lube, but can't say I've seen any significant reduction in seal failures with it.

yeah don it probably does make a big differance

[wally 2]

It's nuts ! That with all the TM lower units that are out there . And most guys change their own lower unit oil . That you can't find a video on YouTube of anyone that is doing it right . Or really any info about it . The mechanic working on my boat now . Said you should keep your lower unit at a 20 degree angle when you fill it . That gives you that 2oz space . Good to know