1991 200 HP trxrp lower unit leak test

[Fjbango]

I got water inside the lower unit and see no damage in the seals or any crack in the lower unit. Before replacing everything I would like to make a pressure leak test.
My YAMAHA SERVICE MANUAL states in page 6-44 the lower unit leakage test is done by applying air pressure for 10 secs and check that it holds. The specified test pressure, and I quote, is:

"1.0 kgf/sq.cm, 2.2 PSI, 1.020 bar"

BUT if you check on any unit conversions table:

1 kgf/sq. cm = 14.2233433 PSI = 0.980665 bar

So the pressure value is different in all three units used.

The following thread http://forums.iboats.com/showthread.php?t=140158
has a posting from Rodbolt stating "..the older v4 and v6 units only tested to 2.2 pounds.the newer jumped to the 14.2. "

2.2 is what shows my "older" service manual; 14.2 is the actual equivalence of 1 kgf/sq.cm

Does that means that Yamaha corrected the conversion in the newer manuals ??
what should be the test pressure?

Any help will be appreciated

Frank Bango
MIami FL.

 

[Fjbango]

Re: 1991 200 HP trxrp lower unit leak test

No Ideas ??? C'mon guys!
I was searching the manual looking for any phone number or email address, hoping I can ask the editors but nope, none!.

I guess I will use the 1 Kgf/sq.cm = 14.2 psi. It is an old motor. If it holds anything more that 10 psi I will take it back to sea and recheck the oil after my first trip.

Any comment will be welcomed! Please!

Frank

 

[david_r]

Re: 1991 200 HP trxrp lower unit leak test

sorry i cant answer you question about the 3 measurements...... and i can see your dilemma in wanting to make sure it holds enough pressure so when things get moving and the lube heats up and expands that it doesnt leak.


when you change the lube do you change the o-ring/gaskets every time?

did you remove the prop to make sure you didnt have any fishing line wrapped around the prop shaft?

are there any visible signs of leakage?

i would not go over the 2.2 as listed in the manual..... take the lu off and get a trash can/barrel and put a little air in the lu then hold it under water to see if any bubbles come up.... it shouldnt take a whole lot of pressure for air to bubble out of a leak.

from what i have read a pressure test is mostly done after new seals have been installed....... but i could be mistaken.....

now if you do not replace the gaskets or have a doubt about how tight the drain/fill screws were i would just replace those gaskets refill the lube and go for a ride then check it after a trip or 2..... you wont lose much oil by only removing the lower screw to check for water, and its best if it has set for a while so the water can settle.. or if it has a milky color you can tell it has water in it.

 

[Fjbango]

Re: 1991 200 HP trxrp lower unit leak test

Thanks David for your input.

The idea of doing the pressure test before replacing any seal is it identify if there are any leaks through the seals or if there is any "crack" in the lower unit.
If the unit is cracked the repair takes a different turn. I plan to repeat the pressure test AFTER the seals are replaced too.

I can't see any crack but I can't see any bad seal either, so I am not sure where the water in the LU came from.

I removed the propeller and there was no fishing lines coiled around the seal and the seal there do not seems to be damaged.

The water I found was totally separated from the oil in the LU, I mean I start draining the LU and only water came out (about 3/4 cup) and then start to pour out the oil. I saved everything and put it in a bottle and then put a strong magnet suspended in the oil to see if I can get some metallic particles but no, there are no chunks of metal not even small powder like particles.

I have the impression like the water came inside the LU either short before turning the engine off or even later during I was washing the engine w/ the hose.

I guess the best way to bring it back to life is to thorough check for cracks, if not any, then replace all seals, gaskets and o-rings and take it to the sea and check what happens.

Thanks

 

[Fjbango]

Re: 1991 200 HP trxrp lower unit leak test

completed the pressure test today witout replacing ANY old part (o-rings, seals etc.).

I was able to presuurize up to 6 psi before it strated to leak.

I think I will take this as good, will replace the seals and o-rings and tale the engine to the water, see what happens.

Thanks dDavid for your input

FRank