Yup. The exhaust elbow would be my first guess, especially if you have not cleaned it in 700 engine hours. Impeller would be my second guess.
You are looking at the right symptom, insufficient water flow. But you are looking at the intake side of the water flow. With Yanmars the problem is more commonly on the exit side. My friend, who is a diesel engine mechanic that helped me diagnose a similar problem on a 2GMF13 about a month ago, says he runs a small rod through the small elbow where water gets injected into the exhaust elbow every 50 hours or at least once a year on the Yanmar in his J/30. According to him dislodging the carbon buildup is routine maintenance, and if not done leads to the water passage being plugged. Rick Brass Washington, NC From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Jerome Tauber via CnC-List Sent: Monday, May 04, 2015 9:48 PM To: Tom Buscaglia; cnc-list@cnc-list.com Subject: Re: Stus-List Overheating as high RPM only Exhaust elbow. Check for clogging. Yanmar recommends replacement every 7 or do years. If clogged engine will overheat at high rpm. Jerry J&J. Sent from my iPhone On May 4, 2015, at 9:19 PM, Tom Buscaglia via CnC-List <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> > wrote: We did a run last weekend to a local harbor for the weekend. Wind was fluky and it was a short trip so we were motoring. Alera has a Yanmar 3HM35 with around 700 original hours and was running fine at our usual cruising RPM of 26-2800 on the tach. The hot alarm went off and I let her cool down and then ran at a lower ROM (1800 or so) and no more alarms. When I got to our destination, I cleaned out the raw water trap as it was pretty crapped up. On the way back the alarm went off again but this time all I had to do was throttle back to around 2200 and it was fine. Much less steam/smoke that on the way out. Today I checked the fan belt on the pump and it was a little loose so I tightened that. I'll be getting her hauled next week for a pressure wash, prop grease and zinc replacement, and will check the intake then. Aside from the intake, belt and crap trap, anything else I should check? Tom B Tom Buscaglia SV Alera 1990 C&C 37+/40 Vashon Island WA (206) 463-9200 www.sv-alera.com <http://www.sv-alera.com/> _______________________________________________ Email address: CnC-List@cnc-list.com <mailto:CnC-List@cnc-list.com> To change your list preferences, including unsubscribing -- go to the bottom of page at: http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com
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