Kevin, Fill the fuel tank with 6 to 10 gallons of fresh fuel, try it out, and get back to us. Check your racor filter for air. Low fuel/air in the line/water in the line can all cause rough operation. These Yanmars have a lot of backlash in the engine and when you get rough operations the clutch plate springs can bang. If you have a loose/broken/soft engine mount it can allow the engine to bang around pretty good too.
Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Sat, May 26, 2018, 2:30 PM Kevin Paxton via CnC-List < cnc-list@cnc-list.com> wrote: > Hey Everyone, > > Well we were lucky enough to be able to take out our 34 this past > Wednesday for the Blue Angels show in Annapolis. On our way back our Yanmar > 3GMF would occasionally make a knocking sound. I'm hoping you guys might > know what could have caused it. > > When it happened: > * We were about to enter into the mouth of the Magothy and I was taking > down the main. My wife had the helm and yelled up saying that something > didn't sound right with the engine. She throttled down and when I got back > everything sounded ok. She said that it sounded like it was going to die. > Like it was running out of fuel. > * We kept it running slowly for a bit without issue. Then I tried to speed > us up again. After about 5-10 mins it started making the noise again. To me > it sounded like a loud knocking or banging sound. I immediately reduced > power again and it immediately went away. > > Conditions: > * At the time it started occurring we had about 1/8 of a tank of fuel. > * Heavy, choppy waves for a large portion of our trip due to lots of power > boats. However, at the time it occurred, seas were calm. > * At start up after we sailed for a bit the prop had trouble opening and I > had to reduce power a couple of times to get it to open. > > Observations: > * I didn't see anything incorrect or worrysome during operation. > * No leaking oil, fuel, or water. > * Racor water separator doesn't show any water in the bowl. A little gunk > in the bottom but not much. > * When power was reduced, everything sounded normal and operated normal. > > Thoughts/Questions: > * Could low fuel/dirty fuel/water in fuel make this happen? > * Could this be more of a vibration from the prop not opening properly? If > that's the case, could it be indicative of something in the strut or > cutlass bearing? We have in the past had A LOT of problems with the prop > not opening. > * I did notice that during operation on the way back that occasionally the > undulation of the waves caused some stress. I'm assuming just because of > stresses on the prop. > > Today I filled up the tank and started it up in the slip. It started > immediately and didn't sound like anything was wrong. I brought the > throttle up and down and everything sounds absolutely fine. So I'm at a bit > of a loss as to what to check/do. I do know that I still need to change the > oil and I am planning on changing the fuel filters as well. > > I did notice that I am able to see the notch in the prop shaft where it > meets the gearbox. There does not seem to be anything on the shaft that > would indicate that it shifted at all though. Is this normal? > > Would love some help from some of the yanmar experts on here please. > > Kevin Paxton > '82 34 #473 > Japhys Spirit > Cornfield Creek, Pasadena, MD > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > >
_______________________________________________ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
