This list is a fabulous resource for problems of that sort. Thank you Stu!
From: CnC-List [mailto:[email protected]] On Behalf Of Josh Muckley via CnC-List Sent: Thursday, December 06, 2018 3:45 PM To: C&C List Cc: Josh Muckley Subject: Re: Stus-List Yanmar 3HM35F repairing oil leaks 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]<mailto:[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]<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
