>... and again discovered the coolant tank full and the same oil mix. Am >assuming the head gasket is blown - again. The mechanic has not looked at it >yet. Obviously, something is "wrong."
I'm not convinced a slightly over pitched prop would encourage an otherwise healthy engine to blow its head gasket twice over 5 years. Were there any signs of pitting, cracking, or corrosion on either the block or the head when the gasket was changed in 2010? Back when I owned 1/2 of a 1981 C&C 36 powered with the original Yanmar 3 cylinder engine I had both a failed head gasket, a crack in the cylinder head, and block corrosion related to the head gasket failure. The cracks in the cylinder head where along the side of the combustion chamber. The symptoms included the oil/soot in the coolant, some coolant in the lube oil, and hard starting when cold. We chose to replace the older Yanmar design with a new Yanmar as spare parts were getting harder to find and many of the parts attached to the block (starter, alternator, exhaust etc.) were in poor condition. My recommendation is to have your mechanic look very close at the head and block to make sure then is not an underlying problem that will return regardless of the prop's pitch. Martin Calypso 1971 C&C 43 Seattle -----Original Message----- From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Nauset Beach via CnC-List Sent: Tuesday, July 21, 2015 7:31 AM To: cnc-list@cnc-list.com Cc: Nauset Beach Subject: Stus-List Best Engine>Yanmar 3GM + Prop? John, Mike and any others with a Yanmar 3GM30F What is the make, diameter and pitch of your props, and can you get to the one hour rated RPM of 3600? Back in 2010 I had an engine overheat alarm and discovered the coolant overflow tank was full and had an amount of oily substance mixed in. There was very little coolant left in the engine. The mechanic discovered a blown head gasket was the cause. The head was sent to a shop to be "rebuilt" and a few other parts replaced. Last month [just after Edd's engine woes came to light] I had another overheat alarm, and again discovered the coolant tank full and the same oil mix. Am assuming the head gasket is blown - again. The mechanic has not looked at it yet. Obviously, something is "wrong." The July edition of Cruising World had a timely article about props and stated an over pitched prop puts additional wear on the engine and can lead to cavitation. Nothing new there but started a possible theory. I have not had dark exhaust so did not think the prop was over-pitched, but there is some pitting on the prop blades so maybe there is cavitation and an over loaded engine. Also have excessive vibration so the clues seem to be going in that direction. I rarely take the engine up to 3000 RPM though did have a several hour delivery at 3200 this spring. Have never tried but do not think I could get up to 3600. [Have read the Yanmar tach's are not all that accurate and have not had the RPM's verified independently.] Still this seems to be another indicator the prop may be over pitched. I originally had a Martec folding 16 D x 14 P prop though after the lack of much reverse led to a "near miss" incident I replaced it in 2002 with a Flex-O-Fold with a 16 D x 13 P at the recommendation of Flex o Fold. The reduction is 2.61. Am thinking the increased surface area Flex prop is overloading the engine even though the pitch was decreased by 1" compared to the Martec. Anyone have any thoughts? Thanks, Brian _______________________________________________ Email address: 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
