Passive Water Flow In 4.3 Mercruiser

[rcmpvet]

I am using the word "passive" as opposed to when the engine is running and pumping water. Discovered a leak in the bilge area, roughly 2 gallons/24 hours. I have been able to isolate it to the port engine itself as the ingress of water increases to about 1 gallon/hour when engine is running.

My son (mechanic) will be down this weekend with his scope, etc to try and find the exact source however from what I can see when using a camera is that it could just be a gasket, at least I hope that is all.

My question is thus; I do not wish to have to lift the vessel out of the water to do repairs, but if I remove the water intake hose and plug same would I still get some "passive" water intrusion, ie from exhaust area. Recalling my high school physics the intrusion should be minimal if any and can probably be handled by the bilge pumps. I have previously been able to change a thermostat without water coming up through the housing itself.

Thanks in advance, I tried to search for a possible answer but most just address water pump failures, etc.

 

[alldodge]

Don't know your boat and with a 4.3 I'm assuming a Alpha drive. If the water leak is at the transom raw water line, you may not be able to remove it and stay dry. You could remove and plug, but I would leave the fitting on the transom, and just plug the hose attached to it, or lift it high.

The exhaust should not be a problem unless your boat sits really low in the water. If it does sit low in reference to the motor, then you should have exhaust riser extensions. If you have no extensions, then you should be able to remove the exhaust boots going to the Y pipe

 

[Scott Danforth]

it would help if we knew what boat, what vintage, etc

however, the common sources for leaks in a boat with an alpha outdrive

• flappers burned off, and dropped down the y-pipe wearing a hole thru the y-pipe - fix - remove drive, remove motor, replace y-pipe, install motor, align motor, install drive
• bellows leaking - fix - remove drive, replace bellows (and most likely gimbal bearing and u-joints), align motor, install drive
• loose transom shield bolts - fix- remove drive, remove motor, assess as needed, tighten bolts, install motor, align motor, install drive
• failed transom shield gasket - fix- remove drive, remove motor, remove transom shield, replace gasket, install transom shield, install motor, align motor, install drive
• failed/rotted transom - fix- remove drive, remove motor, remove transom shield, rebuild transom-stringers-bulkheads-replace gasket, install transom shield, install motor, align motor, install drive
• bad hose - fix - replace hose.

you will notice that most of those require removing the drive. that requires hauling your boat out.

when was the last bellows service?
when was the last drive annual removal?

 

[rcmpvet]

Maybe I was not clear, the leak is in the engine itself, the water in the bilge was only my first indication that I was monitoring over the past couple of days. When I start the engine and then shut it down I can see the water trickling into the bilge area at the back of the engine, near the mounts. However, the water starts somewhere forward of the exhaust area and above the frost plugs, that is the best I can see with my camera. Both my son and I agree it is somewhere on the engine itself.

Again, my only concern is water still coming into the engine after we drain it and start to remove the manifolds to better see the area. From what AllDodge stated it sounds as if we are relatively safe to do the removal of some parts without having to lift the boat out of the water.

Incidentally, all the work that Scott stated has been done in the past two years and drives are pulled and serviced every winter by myself.

 

[rcmpvet]

Sorry for delay in getting back, computer crashed. My son looked at things today, definitely better eyes than mine. The water leak is in the Oil/Power steering cooler, Part #9935A2, a small pin hole on top. Nothing that can't be fixed on board and in the water, once I get the part.

Again thanks to all.