J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Weird one

Hi all,
This one is strange, however I've noticed it twice now. After sailing in somewhat stronger weather, say 15k winds and about 3-5 waves, I noticed that when engaging the engine after dropping the sales, the engine didn't pump water. The first time this happened, we were beating into the wind until we rounded the Island, I engaged the engine prior to dropping the sails and didn't see it pumping water, I shut it off and decided to sail into the channel and subsequent harbour which were both flat calm and very sheltered, this took about another 10 minutes or so. I decided to try the engine again before dropping anchor and pulling apart the cooling system and the engine started pumping as per normal. About 5 days later I did the return trip, downwind but with same size seas, so a bit rolly, the engine was pumping very well before going under sail, however when I got to the mouth of the bay where I keep her moored, and engaged the engine, it wasn't pumping water again, nor did it for the 150 yards to get to my mooring (Pressed for time and went slowly as I didn't have time to trouble shoot given how close the mooring was). I suspect that if I go out to the boat this weekend and start her up, the engine will pump water again. So I"m wondering if anyone else had seen this and if it's some sort of reverse suction occurring when sailing in a bit of a chop? Very strange. The impeller was replaced about 5 months ago so still some life left I would imagine.....

Any thoughts?

The engine intake is on the stbd side so there is a chance you may have had the suction out of the water. This occurred on Rhapsody while motor sailing and I know others have experienced similar.

Nope, she was pumping water for about 1/2 an hour on the return trip, taking the chop broadside without issue and then it was downwind with the engine off for about 2.5 hours. Once in the bay when I restarted the engine and dropped the sails, the hull was on 0 degrees so the intake was in plenty of water, I would also imagine that the intake never came out of the water on the downward leg either.

Then you may have either a worn impeller, or a vacuum leak. Try these steps
1. Clean out the strainer and change the cover gasket. This is a common air leak source if the cover is not mated securely to the gasket.
2. Check that all hose connections are securely fastened and clamped. Make sure the hoses have not hardened with age
3. Make sure the impeller on the water pump is good and the case on the pump that the impeller mates against is not scored. It is a good idea to replace the impeller every couple of years.

Do NOT, under any circumstances, Reverse the rotation if any rubber impeller. The blades will come off! ( Fourty years in small boat repair )

Bob is 100% correct on the reverse rotation.

If you have a problem getting it in the housing, use soap and water or a non-petroleum grease made for that purpose. When you pull the old impeller out, look at the way the vanes are oriented and install the new impeller the same way.

Thanks Gents, I'm heading back out to her tomorrow and will go over everything you suggested, as well as post my findings here. Really appreciate this forum and it's members.

Oh following up on this, sorry for the delay. After taking apart the water pump, it was indeed the impeller. One of the blades had broken off so was now covering up the exhaust hole.