jb weld leaking oil

[dueynetsell]

hey guys,
I am a college student with very little knowledge of boat engines, but with so little funds i have to pretty much do everything my self... so last winter my lower unit cracked due to water being in it (lesson learned), so i applied jb weld to the crack which holds just fine when i am only idling( which i am doing most of the time), but when i run it on plane for any length of time, a little bit of gear lube leaks through the jb weld...

Is this likely because i did not apply the jb weld as well as i should have?
or could it be that for some reason my lower unit is getting way too hot than it should be?

also what would be the best way to remove the jb weld if i need to do it again or finally get it welded?

 

[kfa4303]

Re: jb weld leaking oil

Hi dueynetsell. I'm a student too, so I feel your pain. What is the model, year of your motor? Any pics? Your gears shouldn't be getting too hot assuming it's holding the proper amount of oil. However, if oil can get out, water can get in, which is what could really damage your gears. I guess there are a couple things you could try. Starting with the simplest (cheapest) thing first. You could try to put just a bit more JB weld over the leaking bit and hope for the best. You could cut out/remove the old JB and get it properly welded, but I think you might be best served by trying to get a new/donor LU from another motor. It would probably cost the same as haveing it professionally welded and you would get all the extra bits that come in the donor LU. Check c-list, ebay, and local repair shops. You might be surprised how little you can get a new LU for. Good luck. Keep us posted.

 

[1946Zephyr]

Re: jb weld leaking oil

What model and year of motor are you working on? Some motors, it is worth the money to replace the lower unit, if it's in that bad of shape.

 

[carholme]

Re: jb weld leaking oil

Whatever way you choose to go, the probability is that the crack was not cleaned well originally and still retained some oil. In my experience, the only sure way to JBWeld is to flush the crack thoroughly with laquer thinners as well as the surrounding area on the outside and the inside. Fill the crack with JBWeld and tap it back to as close an original position as possible, then really use pressure on your spatula to try and force more JB into the crack.
Then on both the inside and outside lay up a nice covering of the area and smooth it down.

Any residual oil that may have been left in the crack is a channel and it will find it's way out.

Gerry

 

[fishrdan]

Re: jb weld leaking oil

the only sure way to JBWeld is to flush the crack thoroughly with laquer thinners as well as the surrounding area on the outside and the inside. Fill the crack with JBWeld and tap it back to as close an original position as possible, then really use pressure on your spatula to try and force more JB into the crack.

^^^ Yup

 

[DargelJohn]

Re: jb weld leaking oil

All good advice. Something else you might consider is using Bondo (body filler). You could clean off a larger area and put on a thicker layer.

 

[dueynetsell]

Re: jb weld leaking oil

thanks everyone for the responses, actually the 2nd time i've applied the jb weld with the same result, however that by no means means that it was applied as well as it should have been. The motor is a 1989 evinrude 175 hp...
I guess my biggest question is why does it only leak through after running it WOT?

 

[DargelJohn]

Re: jb weld leaking oil

Depending on how large the crack is and the position, at WOT, it is probably flexing the casing and breaking the JB Weld.

 

[5150abf]

Re: jb weld leaking oil

I ran jb on a lower for a few years and never had a problem so I think yu may not have prepped it well enough, you have to get it really clean and scuff the crap out of it, I used a file to get it really scuffed up, maybe try one more time and maybe open the crack abit to get more of a seal, just V it out a little, maybe 1/8'' adn use laquer thinner as carholme suggested.

No Bondo, it absorbs water and has no strength.

 

[dazk14]

Re: jb weld leaking oil

+2 no Bondo, it also doesn't stick like epoxy.

You need the prepped area to have as much tooth/scratches as possible. It must be PERFECTLY clean. Acetone also works well.

Spend the $15 bucks and get a 2oz container of grey (not white) Marine-Tex. This adheres better than JB and is the choice of cracked engine blocks all over the world.

Mix the entire amount, so you ensure a perfect ratio.

You may want to post a pic when you get it prepped and the guys here will tell you if it's got enough tooth.

 

[fishrdan]

Re: jb weld leaking oil

I guess my biggest question is why does it only leak through after running it WOT?

Depending on how large the crack is and the position, at WOT, it is probably flexing the casing and breaking the JB Weld.

Or, when the gear lube (and air pocket) heats up, it expands. The weak JB weld job isn't holding the pressure.

 

[Mas]

Re: jb weld leaking oil

How much would welding it cost??

Mas

 

[phoodieman]

Re: jb weld leaking oil

Or, when the gear lube (and air pocket) heats up, it expands. The weak JB weld job isn't holding the pressure.

I had a large (3 inch) crack that I had welded up. The welder heated the skeg up with a torch and poured isopropyl over it several times. (Why it didn't catch on fire I don't know). I watched him tig weld it and I could still see the gear oil purge out as he was welding. He did a good job, but I had two pin holes left after he welded. I drilled out the pin holes and pushed JB weld up and into the inside and let it mushroom out. Even after that when I had the motor stored in the down position I would have drops of gear oil coming off the bottom of the skeg and after two or three hours of running I would have water in the gear oil. (Very little though, just enough to know I had water coming in). The last time I had the LU apart I cleaned the inside of the skeg thoroughly and put a bead of JB over the entire area of where the weld had penetrated into the inside. I have ran the motor seven or eight hours on three separate trips checking the oil after the run each time and I am glad to say I have good clear gear oil now.

phoodieman

 

[boobie]

Re: jb weld leaking oil

I'll still vote for the gray Marine Tex. The trick is to have everything good and clean and dry and the surface roughed up. I've used Marine Tex for yrs and had very good luck with it. Even used it to repair cracked blocks on stern drive mtrs.

 

[Joe Reeves]

Re: jb weld leaking oil

As a couple members stated above (Dazk & Boobie), go with the "Gray" Marine-Tex, but for what it cost, I suggest that you mix only what you need.

Use Lacquer Thinner or Acetone to thoroughly clean the crack, then apply the Marine-Tex as per the instructions. If the crack is cold, heat it up slightly (Not Hot) to a point whereas it is warm.