M25 Rear main seal leak or...

[Thecatalinaproject]

Hey All,

Just got a free Catalina 30 (I know, I know: nothing more expensive than a free boat!) The boat had a couple of feet of water in it when I got to it. The water did not reach the air intake fortunately, and the oil was clean.

When I got the boat running, however, I noticed a significant amount of a substance most similar to pottery clay oozing out of the bell housing hole on the side.

I hoisted the engine, pulled the transmission, the bell housing the damper and the fly wheel and cleaned an insane amount of the nastiest goop you've ever see out of there but I can't tell where it came from. Rear transmission seal seems to be good. Rear main seal looks like possibly a small leak. After cleanup, the wettest area I can see is seemingly around the bottom of the plate that is around the rear main seal.

I'm wondering if the gasket of the plate that holds the crank in place could be to blame? I don't see any info on that being a regular cause of a leak of this proportion.

I'm temped to replace: the rear main seal, the oil pan gasket and the valve cover gasket just to be certain i've dealt with the issue while I have it pulled apart, but if it's just rear main seal that would be nice!

Any guidance is appreciated!

 

[kloudie1]

Welcome to the forum! I am not very familiar with that engine but your picture shows a leaky rear main seal for sure.
But whi.e you are messing around with it, not much extra effort is needed to do the other two gaskets and be done .
Again, Welcome and enjoy the new toy!

 

[Hayden Watson]

Given you have it out, a rear main seal would be prudent. Have you checked the fluid in the gearbox. They often fill with water with partially submerged even when the engine does not. The gearbox uses Dextron ATF.

 

[Thecatalinaproject]

Welcome to the forum! I am not very familiar with that engine but your picture shows a leaky rear main seal for sure.
But whi.e you are messing around with it, not much extra effort is needed to do the other two gaskets and be done .
Again, Welcome and enjoy the new toy!

Appreciate you taking a look. Will definitely just go ahead and swap them out!

 

[Thecatalinaproject]

Given you have it out, a rear main seal would be prudent. Have you checked the fluid in the gearbox. They often fill with water with partially submerged even when the engine does not. The gearbox uses Dextron ATF.

It definitely took on water and I pumped the sludge out of it, and flushed it multiple times. The rear seal on the gear box looks like there is a little space between the spline and the seal, but nothing is leaking out. I might as well do that one as well and be done with it!

 

[Hayden Watson]

It definitely took on water and I pumped the sludge out of it, and flushed it multiple times. The rear seal on the gear box looks like there is a little space between the spline and the seal, but nothing is leaking out. I might as well do that one as well and be done with it!

Do you have access to the full shop manuals for the Universal M25 and the Hurth HBW-50? If not, let me know and I can hook you up with a link.

 

[Hayden Watson]

It definitely took on water and I pumped the sludge out of it, and flushed it multiple times. The rear seal on the gear box looks like there is a little space between the spline and the seal, but nothing is leaking out. I might as well do that one as well and be done with it!

A good mixture for cleaning out the sludge from the gearbox is a 50/50 mix of ATF and acetone. Since the box is out of the boat. you pour some in, shake it around, hand turn the input shaft in forward and reverse and dump it out. Reince and repeat until what comes out, looks like what went in. Then fill and drain several times with straight ATF to get all of the acetone out.