Do I need to replace ALL seals on LU?

I've got water in my lower unit. I've checked to make sure it wasn't just the fill & vent plug seals. Local parts guy seem to suggest that I need only to replace the seals on the prop end as they may have been damaged by fishing line or some other such object. Does this sound kosher? Can I change that set of seals without removing the LU? I've had the LU off before to change the impeller, but I stopped short of changing the seals at the time because all those gizmos on exploded diagram looked intimidating. <br />Should I dig into it anyway?

Re: Do I need to replace ALL seals on LU?

Hi, <br /><br />why not pressure test it to find out where the leak is?? then take it from there. For example it could easily be a bad seal in the water pump base... <br /><br />Brent

Re: Do I need to replace ALL seals on LU?

Thanks BF,<br />Sounds like a great idea. How do I do this? Is there special equipment required? Can I do it with a bicycle pump and some sort of special vent plug (if so, any idea where I can get one)? How do you detect where the leak comes from, soapy water? I assume this means removing the LU, correct?<br />Thanks for the help.<br />-Joe

Re: Do I need to replace ALL seals on LU?

joew, You didn't say what your motor is.Generally,if it is more than 2 or 3 years old,replace all the seals,gaskets,and o rings.They are all old.<br /> If the job intimidates you,pull the lower unit and take it to a shop.You'll save a least a portion of the bill.<br /> If you decide to do the work yourself,get the Factory manual.<br />DHP

Re: Do I need to replace ALL seals on LU?

Joew, Two of the seals on the lower unit are easy to replace. These are the waterpump base o ring and the waterpump base driveshaft seal. I would replace these (and the waterpump impeller and gaskets) and see what happens. I still have the original prop seals in from my 1977 Merc., but have replaced the other two several times.

Re: Do I need to replace ALL seals on LU?

Hi again,<br /><br />To pressure test you take the LU off (that's the first step for whatever you do), as you guessed, find a way to replace either the vent or drain plug with something that will hold air. If you have one of those little pumps for pumping oil into the LU, you can borrow the end that screws into the fill plug to use (with the length of tubing), or in a pinch I've used a small rubber stopper and run fine stiff tubing through a hole I drilled through the stopper. Then use something (I use a syringe, but bike pump would also work) to pump air into the LU. DON'T OVER DO IT. A shop will usually pressure test with 10 psi I think. If you use more, you could blow out otherwise good seals. T-ing on a pressure guage to your pump/syringe line is helpful, especially later to confirm that the unit is holding pressure well. Since you know you have a leak, yours won't hold pressure so if you have a guage attached, you'll see the pressure run down right away. Then keep your tubing/pump contraption attached and submerge the LU in water... I've used a bathtub if motor is small and wifey is not watching, or a little "kiddie pool" for my 150 hp (big cav plate). Once underwater, give a pump or two of air and see where the bubbles come from. Fix leaky spot (sometimes find something surprising - see below) and then pressure test again. Now the LU should hold 5-10 psi. This is where you need to be careful not to overpressurize and where a having a pressure gauge in your tubing "contraption" is needed... leaving a foot or two of tubing length between the LU and the pump/pressure gauge is helpful, since you don't want to submerge those with the LU.<br /><br />Just this week doing a pressure test kept me from pulling seals that are fine on motor that is new-to-me... turned out it was a weird leak from a screw hole that looks to have been drilled all the way through when it should've been blind. <br /><br />Anyway... good luck!<br /><br />Brent

Re: Do I need to replace ALL seals on LU?

when looking at this (long) it seems like a big job.. but once you've made up the tubing/pressure gauge contraption, the part that takes the longest is filling the bathtub! (and fixing the leak).<br /><br />Keep the contraption someplace... someday you'll use it again<br /><br />B

Re: Do I need to replace ALL seals on LU?

BF gave you good workabke advice. I have been just through the whole process, using much of the same type of "equipment" -- and they work. You may want to put a piece of heavy carpet in the tub to protect the finish and your good standing with your mate. It's a hassle, but what else can a person do, unless you have the $$$ to go to a shop. When you drop the lower unit, it's usually best to do it in neutral, and reinstall it in the same. Put a heavy cushion under the LU, because it may drop really fast.

Re: Do I need to replace ALL seals on LU?

pressure testing will test the o rings and half the seals. both shafts have 2 seals-one keeps oil in and the other keeps water out. a vacuum test will be needed to do a thorough job. this is done the same way as the pressure test-except using a vacuum pump.

Re: Do I need to replace ALL seals on LU?

True enough and pressure testing will also test the gaskets. In most cases, it will reveal the source of the problem.