Locating small seawater leak on Yanmar 4JH2E

Oct 26, 2010
1,883
Hunter 40.5 Beaufort, SC
As you can see I have an obvious seawater leak somewhere on the starboard side of my Yanmar 4JH2E. It appears to be a drip of some sort. I'm away from the boat but will investigate when I get back. I found this when I was changing the oil this fall. Is anyone aware of the possilbe location of the leak on this side of the engine? I"m thinking it might be the "vent" tube from my PSS dripless shaft seal? Do most people have a bottle of some sort at the end of the vent tube?
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Jan 11, 2014
11,321
Sabre 362 113 Fair Haven, NY
On my 3JH2E I found similar corrosion. It is right below the vent for the PSS shaft seal. When the boat is pushed hard astern water can back up through the vent and into the engine compartment.

Either in a post or on his site, @Maine Sail had a solution where the water ran into a bottle. There needs to be an air break above the waterline to prevent siphoning.
 
Sep 26, 2008
546
Hunter 340 0 Wickford, RI
On my 340, the PSS Vent tube runs up to the back of the engine compartment. I installed a 1 pint plastic bottle, much like the overflow type for a car radiator or our over flow bottles for our engine antifreeze.
Like Dave stated....in “reverse” water will flow up an out of that tube and right into the compartment. The bottle handles this problem nicely.
I’ll take a photo and post it here later this week when I go back to the boat to show you.
 
Sep 25, 2008
957
Macgregor & Island Packet VENTURE 25 & IP-38 NORTH EAST, MD
I would think that part of the engine would be pretty far away from the PSS seal. Why would the vent be way up there? The only sea water at the front is the raw water pump, but its on the other side of the engine. Where does your raw water line run? Maybe there is a small pin hole in the line, and sprays when the engine is running?
 
Jan 11, 2014
11,321
Sabre 362 113 Fair Haven, NY
I would think that part of the engine would be pretty far away from the PSS seal. Why would the vent be way up there? The only sea water at the front is the raw water pump, but its on the other side of the engine. Where does your raw water line run? Maybe there is a small pin hole in the line, and sprays when the engine is running?
The vent for a PSS seal has to end above the waterline for obvious reasons. The nearest direct run to a place that is always above the waterline in most installations is somewhere in the engine compartment.
 
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Sep 26, 2008
546
Hunter 340 0 Wickford, RI
Dave,s right. It has to be above the waterline and it's really not that far away and works well there.
I agree, can't tell from your photo but is most likely the cause.
I should add, I have never seen more than few tablespoons of water in the bottle, but it doesn't take much water to start causing rust. Your boat probably backs up a lot better than mine too, so you may get more water in the line than I do. If you go in reverse longer and farther than I do.

I couldn't back my boat in a straight line for more than 10 feet under the calmest of conditions, on a bet. I have a three blade prop, but the propwalk is terrible on my 340.
I'll post photos later this weekend for you to see. You can test it though by temporarily taping a plastic glass in there at the end of the line and go in reverse and see what you get.
 
Jan 11, 2014
11,321
Sabre 362 113 Fair Haven, NY
Dave,s right. It has to be above the waterline and it's really not that far away and works well there.
I agree, can't tell from your photo but is most likely the cause.
I should add, I have never seen more than few tablespoons of water in the bottle, but it doesn't take much water to start causing rust. Your boat probably backs up a lot better than mine too, so you may get more water in the line than I do. If you go in reverse longer and farther than I do.

I couldn't back my boat in a straight line for more than 10 feet under the calmest of conditions, on a bet. I have a three blade prop, but the propwalk is terrible on my 340.
I'll post photos later this weekend for you to see. You can test it though by temporarily taping a plastic glass in there at the end of the line and go in reverse and see what you get.
Disclaimer: I have not observed this, so it is a bit speculative.

As the boat is docked or brought up to a mooring, it is not unusual to give the motor a burst in reverse, that burst drives the water up into the seal and up the vent hose and out. Since it is a very short burst only a little water comes out, the engine is shut down and the water does its job on the motor. That would explain only have a few tablespoons of water show up in the bottle and since the lower part of the engine is relatively cool, it does not evaporate immediately on contact.
 
Sep 26, 2008
546
Hunter 340 0 Wickford, RI
smokey73,
Here are some pictures of my PSS Vent line and overflow bottle. The pictures are a little dark at the PSS itself but you can see how the vent line follows the Fuel Line into the engine compartment. I held the bottle on with 2 zip ties screwed into the back firewall, then pull them very tight.
I drilled the cap a little smaller than the hose, to securely hold the hose in the bottle. So any vibration wouldn't let it come loose. The bottle never fills so weight isn't really an issue. It's a pretty simple setup, avoids a major rust problem down the road and works well.
Hope this helps you design one for yourself.
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