This is an interesting topic as there are many variables that may affect the condition of the impeller. My Yanmar 3QM30 engine typically accumulates a maximum of 100 hours of operation in a sailing season. On most daily outings, the engine runs approximately 15 minutes at each end of the excursion. I have an hour meter and keep track of oil changes and other maintenance items with a reasonable degree of accuracy. Major servicing of filters, oil change, impeller check, etc. is done at winter layup so the engine sits for 5-6 months with clean oil. I also make sure the cooling system has been well flushed with fresh water before starting the winterization process. The current impeller has seen 7 seasons of use and will remain in place for next season.
The boat operates in relatively cold North Atlantic salt water which is generally clean and results in little accumulation of weeds or anything else in the raw water filter. The engine is raw water cooled and during the just completed teardown and rebuild appeared to us to have little corrosion or build up in the block and head. The cause of the excessive blow-by which precipitated the rebuild remains undetermined, but could not be related to insufficient cooling. The impeller, a crucial component, appears to suffer little annual wear and has never catastrophically failed. Perhaps warmer water, higher levels of silt or chemicals, or significantly greater use may have a greater negative effect on and impeller. I have had a number of outboard motors with varying experiences with impellers, most of the negative ones were related to sand intake and salt deposits that were not flushed out properly before storage. Outboards I have owned in fresh water areas have run for years with no impeller problems. As a last comforting thought: if the impeller fails and the engine cannot be run, sails are a fine backup system. Rich Knowles INDIGO - LF38 Halifax, NS From: CnC-List [mailto:[email protected]] On Behalf Of [email protected] Sent: October 19, 2012 10:27 To: [email protected] Subject: Re: Stus-List Miscellaneous -impeller Spend a few bucks and change the impeller with each annual service, the few dollars that it cost will save you grief & money in the end. A senior Yanmar factory tech told me that after a year of two the rubber blades on the impeller will "set" and will decrease in efficiency due to fatigue in the rubber, the blades may not indicate cracks but you can bet they they have lost some flexibility. The Yanmar guy is a good friend & was not trying to me impellers, just offering good advice.... The choice is yours, but if you want go longer than 2 years you may want buy a Sea Tow package... Jack Fitzgerald HONEY C&C 39 TM Savannah, GA In a message dated 10/19/2012 9:16:36 A.M. Eastern Daylight Time, [email protected] writes: I don't have the experience of Rich but I would also lean in that direction. I've changed mine for the first time this summer after 3 years. The impeller looked in perfect condition (no cracks and blades were as flexible as a new one). I kept the old one as a spare and now feel confident that I will only inspect the impeller every spring. I've been told by a mechanic that if the raw water circuit is winterized using antifreeze (vs. drained), the impeller holds up very well. Since our impeller spends more than half the year in antifreeze, this might explain the durability! I also reasoned that since we sail on a lake with no commercial traffic and never solo there is little risk in case I have to face an impeller break down: I have a spare and tools on board, I know how to swap them. Sébastien Lemieux Merlot X - C&C 30 mk2 1987 Mooney Bay - Lake Champlain On Oct 18, 2012, at 21:28, Rich Knowles wrote: I check mine each season's end when I winterize. If it looks good, it goes back in. I have installed one new one in 15 years and that includes several runs of a few minutes each year without water. They are pretty durable. I check for cracking. Rich Knowles Indigo. LF38 Halifax On 2012-10-18, at 22:04, Martin DeYoung <[email protected]> wrote: ...how often do you guys change the impeller in the raw water pump? I change Calypso's 4-108 raw water impeller at the start of each season then put the lightly used old one in the spares box. It is also my practice to check the impeller prior to setting off on a longer trip where a sudden loss of cooling might be inconvenient. There has been a year or so where I did not change the impeller in the spring and the impeller perform fine with no significant change in appearance. I change the impeller after each time I forget to open the raw water inlet thru hull valve and allowed the engine to run without cooling water for more than a few minutes. Martin Calypso 1970 C&C 43 Seattle -----Original Message----- From: CnC-List [mailto:[email protected]] On Behalf Of Robert Abbott Sent: Thursday, October 18, 2012 5:24 PM To: [email protected] Subject: Stus-List Miscellaneous Because of excessive mussel growth on my prop and prop shaft the past several seasons, this past Spring I tried something new, namely applying "lanolin" to them....boat was hauled this week and I can report that the lanolin was not very effective.....there were approx. 3 dozen mussels attached to the prop and the prop shaft was covered as well. On another note, applied Micron 66 antifouling paint to the boat this past Spring (have been using Micron CSC for over 12 years).....absolutely no growth of any kind....and specifically no 'slime' which is common with the CSC.....the bottom looks like it did when it was painted in the Spring and I only applied a very light coat of the '66' (actually diluted it approx. 10%)....it is incredible antifouling paint.....only regret is that it is not sold in Canada. And, after 7 sailing seasons, I decided to check the air filter on the Yanmar 2GMF.....took the cover off to discover there was no 'actual filter' in the metal casing...ooops! There will be by next Spring. Lastly, how often do you guys changedthe impeller in the raw water pump? Not what the specs recommend but actually how often.....every year, 2 years, 5 years, 10 years? Bob Abbott AZURA C&C 32 - 84 Halifax, N.S. _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com <http://www.cncphotoalbum.com/> [email protected] _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com [email protected] _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com [email protected] = _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com [email protected]
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