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Old 10-21-2012, 02:04 PM
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JimN JimN is offline
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Originally Posted by Sierra Tango II View Post
Quite honestly i idled for about 40 minutes or so, as it was a beautiful morning, I was enjoying my coffee and it was the last time it was going to be in the water. I just bought the boat about a month ago and put about ten hours on it. I had it checked at the Mastercraft dealer and it checked out fine, including the impeller. I do know about the impeller and asked at the time that it was cecked out if it should be replaced, however the service manager said that because it was the end of the season not to worry about it, but to just keep an eye on the temp gauge for any sudden fluctuation, but replace it when I winterized it. I did not know that the boat was not meant to idle long. What damage occurs with excessive idle time? We actually use it for more than just skiing and probably 2 of the ten hours have been at idle while driving around the lake watching the sunset. I removed everything thus far but have not cranked it over. I was going to change the oil, and tranny fluid, fog it and then crank it over as the last thing that I did. I pulled the entire drain plug out on the block, as I am aware how the passages get clogged with debris. Am I to worry about the pieces of impeller that may or may not be in the block, or are the passages large enough so that the flow will not be restricted?
If it's a beautiful morning, why would you NOT take it out on the water? That speeds up the process and, well,...

If the service manager saw a damaged impeller and DIDN'T replace it, I'd be pretty PO'd. It was already out- what better time to do this? If you have three missing vanes, it can't cool the engine at idle, period. If ANY vanes were missing when the shop looked at it, I would have a serious problem and if they didn't document everything, they'd be on my S-list.

Look at it this way- the choices were to A) replace a bad impeller and you probably wouldn't have had this problem (assuming the oil cooler and raw water hoses are all clear of any obstructions) or B) leave it and let you have this problem. A costs a little but B could be expensive if the exhaust hoses are soft, the flappers and flanges are blistered and the engine cooks. If these aren't at least inspected, you're asking for trouble.

Yes, worry about the missing vanes. Never assume they're not going to cause a problem.

Look, I'm not trying to be the voice of doom and gloom but these are different from car engines because they have a raw water impeller that's not metal and can be damaged and they have rubber exhaust hoses and flappers & plastic exhaust flanges that can be melted by hot exhaust gases. If any water was going through the engine and exhaust, it's possible that they weren't damaged badly because you were only at idle but they still need to be checked and the dealer should have instructed you on what to do WRT long idle times (basically, "don't"). The oil cooler should be checked- if you find weeds and other debris, that's a likely cause for this problem.

Last edited by JimN; 10-21-2012 at 02:12 PM.
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