Mike, I remember helping you with your engine. I was hoping you would chime in. Thanks.
Josh On Thu, Dec 6, 2018, 2:38 PM Hoyt, Mike via CnC-List <[email protected] wrote: > Hi Josh > > > > Those pictures look way to familiar! > > > > In Spring 2016 our 3GM30F failed to start caused by a bend and jamming of > the Governor Flyweight Assembly. This is the device that is moves the > governor as the engine races or stops racing due to prop coming closer to > surface or digging back in. It took about 10 days before we finally > diagnosed the problem and I believe you and I spoke and corresponded quite > a bit at the time (thank you!) I hope that when you replaced the timing > cover that you used something like Loctite on the retaining nut for the > flyweight if you had removed it. On Persistence it was this nut that had > come off over time which caused our problem. > > > > When we finally had the Governor Flyweight Assembly repaired and while we > were waiting for the new timing gasket to arrive (projected wait time of > over two weeks) we decided to reassemble using the hi temp gasket material > available in a tube to test the engine and ensure the problem was > resolved. We planned to then use the new gasket when it arrived. I do not > believe there was any less residue than shown in your photos. Also rather > than risking tinkering with the timing we re-used the existing shims when > reinstalling the HP pump (which we had refurbished while it was out). > There were no leaks and the timing seemed as good as before. In the end we > cancelled the order for the timing gasket and left it as it was and it has > worked very well ever since. > > > > Our 3GM30F at WOT is approx. 3400 RPM and we cruise at 2800RPM. Despite > refurbing all three injectors and the HP pump we still have a puff of black > smoke when starting a very cold engine. My mechanic calls that “Old Yanmar > smoke” > > > > Mike > > Persistence > > Halifax< NS > > > > > > > > *From:* CnC-List [mailto:[email protected]] *On Behalf Of *Josh > Muckley via CnC-List > *Sent:* Thursday, December 06, 2018 2:49 PM > *To:* C&C List > *Cc:* Josh Muckley > *Subject:* Stus-List Yanmar 3HM35F repairing oil leaks > > > > I've been living with oil leaks from around the HP fuel pump and the > timing cover for as long as I've owned the boat (~6.5 years). I finally > had a window of time to make fixing the problem a priority. Everything > went smoothly and the engine is back together and works. I came away with > some observations and questions though. To start here are some > pictures/video of the cover before reinstalling. > > > > https://drive.google.com/folderview?id=1gNX3pjZrcabZ2LUE6rKQAm_M1jVfweR7 > > > > I didn't have power tools available and some tight tolerances on the > engine block only allowed me to get the gasket seating area as clean as you > see it in the pictures. No large or thick chunks and most of the remnants > were feathered in. Anybody have experience getting a seal with this much > residue? > > > > The old gasket was pretty clearly a paper type which had hardened. The > new gasket was a lead/babit/graphite material. Smooth and > semi-reflective. My only hesitation was weather or not to use a sealant. > And the lingering question of, "Why did the OEM change the material?" What > are the benefits of a graphite gasket? RTV sealant or not? I ended up > using just enough RTV sealant on both sides to provide a light smooth coat. > > > > The ignition timing is set by the shims between the HP pump and the timing > cover. There is a timing procedure which I did not perform. Instead, I > simply replaced the shims that were there with new ones of the same > thickness. Anything that messes up that thickness will change the timing > so the use of a THIN sealant is required. Remnants of sealant and damage > to the shims made measuring the thickness of each shim tricky. I tried to > measure a combined thickness of the stack of old shims and compare it to > the thickness of the stack of new shims, because of the combined effects of > damage and sealant, the old stack measured about 50% thicker than the new. > I measured and remeasured and I am extremely confident that I selected the > exact same number and thickness of replacement shims as was installed by > the OEM. I can't recall the source but Blue Locktite is evidently the > recommend sealant. I realize that Locktite makes a number of different > products in various colors, not just thread locker. There was an > associated product number which I was also unable to recall. Instead of > loosing sleep I just used the blue threadlocker which I had laying around. > A light wet coat on both sides of each shim. > > > > While I was in the project I found one of the studs for the HP pump came > out. The nut was seized mid-thread and it appeared that the stud may have > been bottoming out in the timing cover, not providing the required pressure > to that corner of the HP pump. Also contributing to the oil leak. > > > > So the moment of truth arrived and the engine started without a hitch. I > immediately noticed that it seemed to idle a little faster. I let it run > in gear at about 2k rpm for about 2 hours before having confidence to leave > the dock. No oddities except slightly higher idle rpm. While running > around on the water I tried full throttle/rpm to see if there was "more > power". Throttle felt smooth and responsive. It seemed like a higher rpm > was achievable. Typically, with a dirty prop and bottom 2800 or 3000 rpm > is the most I would get before black smoke would develop. This time I got > to about 3400 rpm with no black smoke and more throttle. This all seemed > very positive. If I pushed the throttle just a tad further the engine > would immediately lose significant power and blow black smoke. I realize > that the tachs on these engines are notoriously inaccurate. Mine measures > about 10% low. Without getting the laser tach out I would guess that my > real instantaneous (and momentary) rpm peeked at 3750. The OEM > instantaneous rating is 3600. Thoughts? Is my experience normal for an > engine which exceeds its max RPM or is this more representative of an > engine with too much timing advance? > > > > *Some final thoughts*. > > -I think the mechanic who worked on the engine for the PO during my > purchase caused/failed to fix 3 things. First, in removing the HP pump he > broke the seal and never re-sealed it. Second, he probably > deformed/damaged the shims. Third, he failed to identify/correct the > seized nut on the stud. All of these combined to cause the primary oil > leak. They probably also contributed to a decrease in engine timing. > > -In years past I had made half attempts to fix the leak. This was > punctuated by failing to successfully remove hp pump. As a result no > sealant was able to be applied and the shims where likely to have been > further damaged. I too failed to recognize/correct the seize nut on the > stud. My efforts probably exasperated the existing problems. > > -As I recall, I have had to set the pitch on my max prop lower than that > recommended by the OEM (based on the engine/power and boat/Hull > combination). > > -I now believe that the combined effects have "lifted" the HP pump about > 50% higher than set by the factory causing the timing to be retarded. As a > result the engine has been chronicly under performing. Over the years I've > tweeked other engine and boat parameters around the reduced power (raised > idle speed, lowered prop pitch) and simply accepted it as normal. > > -In the spring, I'll disassemble the prop to compare current settings with > OEM suggested settings. Regardless of the findings I'll probably increase > the pitch 1 step = 2° ~= 200rpm reduction. > > > > Oh yeah, almost forgot. So far, no leaks. > > > > Josh Muckley > > S/V Sea Hawk > > 1989 C&C 37+ > > Solomons, 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
