Hello John. I haven't talked to you in a few months, glad to see you are finally enjoying Miss Muffet. Well, pretty close to enjoying her. I find it difficult to see the sea cocks as the source of your problem. Are these the original sea cocks? Have you contacted Linissen about the problem? Before hauling Miss Muffet, I would do something to remove the sea cocks from the cooling circuit and see if the engines overheat and the impellers die. Is there another sea cock of sufficient size that you could use to obtain cooling water, so that you could run long enough to take a trip to test the impellers? If the problem still happens, it isn't the thru-hull intake. How did you determine that the bubbles started at the thru-hull? Is it possible that there is a crack in the thru-hull or sea-cock which only sucks in air when the volume of water reaches a certain level (at cruising speeds)? But both sea cocks? Sorry I don't have a definitive answer. Hope at least one idea helps. Good luck. Let us all know what fixes things. Norm

My guess is (and since raw water impellers are the same whether they're on a diesel engine, a gas engine, a generator, a macerator, or an impeller driven electric raw water toilet), something--sand, gravel, debris--has seriously scored the macerator housing and/or bent the macerator shaft. The former would chew up the vanes on an impeller...the latter would cause it to wear unevenly till it can no longer hold a prime...a combination would produce exactly the symptoms described. Rebuilding the pump won't fix it...but replacing the housing and impeller shaft will. Peggie Norman Rose wrote: > > Hello John. I haven't talked to you in a few months, glad to see you are > finally enjoying Miss Muffet. Well, pretty close to enjoying her. > > I find it difficult to see the sea cocks as the source of your problem. Are > these the original sea cocks? Have you contacted Linissen about the > problem? Before hauling Miss Muffet, I would do something to remove the > sea cocks from the cooling circuit and see if the engines overheat and > the impellers die. Is there another sea cock of sufficient size that you > could use to obtain cooling water, so that you could run long enough to > take a trip to test the impellers? If the problem still happens, it isn't the > thru-hull intake. > How did you determine that the bubbles started at the thru-hull? Is it > possible that there is a crack in the thru-hull or sea-cock which only > sucks in air when the volume of water reaches a certain level (at cruising > speeds)? But both sea cocks? > Sorry I don't have a definitive answer. Hope at least one idea helps. Good > luck. Let us all know what fixes things. > Norm