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Did The Engine Just Blow Up?

February 25, 2016

Having rounded the northern end of St. Martin, we had nice wind for close reach to St. Barths where we headed for Gustavia harbor to check in.  Note that Cayuga's Yanmar diesel hasn't missed a beat since I fixed a clogged fuel tank pickup tube in mid-ocean in November.  And, to make sure that wouldn't happen again, we got a tank cleaning after arriving in the BVIs.  However, lack of fuel isn't the only thing that can disrupt mechanical propulsion.  

 

We were slowly maneuvering back and forth in the harbor at around 1800-2000 RPM when suddenly -- Clonk! Boom! Bang! -- a nasty racket. I jerked the throttle back to idle and the sounds stopped.  My immediate reaction was imagining a thrown connecting rod in the engine: Yikes$!$!$! But playing around a bit with throttle and gear shift made me think otherwise.  And the clonks and bangs were somewhat random, not very rhythmic, so that also pointed to something other than the internals of the engine.  Experimenting, we discovered we were able to make a couple of knots at around 1,200 RPM without loud noises, so we crept out a half mile into the larger bay, dropped anchor, and shut down the engine.  After getting things squared away, I started the engine again but shifting the transmission into gear had no effect -- there was apparently no connection between the engine and the prop. The only remaining value of the the engine was to charge batteries, but until I understood more, I was afraid to run it and risk the possibility of collateral damage.

 

Opening the engine room, there were no parts laying around or oil covering everything, so that was a good start. However, there was a coating of tiny ferrous particles in the vicinity of the flywheel -- enough to coat the bilge plus a few larger bits of metal laying directly below an opening in the bottom of the flywheel housing.  Also, the transmission oil was clean and at the correct level, so that was a tentative relief. I had previously noticed a little of that fine metal dust, but thought it was just part of the normal wear process of the engine/transmission interface -- it's similar to a pressure plate in vehicle's clutch assembly. Studying the Yanmar books we have on board helped me conclude that the likely culprit was the "damper plate" -- a dinner-plate size device that's bolted to the flywheel and has a splined hole into which fits the input shaft for the transmission.

The tentative diagnosis was that the plate had partially disintegrated, and that the sudden onset of clanking noise occurred when some of the larger pieces broke loose and were getting tossed about inside the flywheel case. At that point, I was comfortable with starting the engine again.  I ran it up to maybe 1,500-1,800 RPM and it ran fine, but I could hear a rubbing/scraping noise that appeared to come from the flywheel area, and I saw an occasional spark through the holes in the flywheel housing -- the same type of spark that comes from a bench grinder!  So, it was quickly obvious that the best option was sail back to St. Martin -- actually to Sint Maarten, the Dutch side -- where there are many options for repair assistance, including a factory-authorized Yanmar dealer with good reviews.  

 

Since it would be a downwind course, we set up the whisker pole.  I weighed anchor and, while Rhoda turned us downwind, I unfurled the jib and off we went through all the boats anchored and moored at St. Barths.  Since we had thought out the maneuver in advance, it only created a minor pucker factor for us, but there were expressions of concern from the crew of a couple of boats that we passed in close quarters on the way out. Once clear of the anchorage and on our way, we hoisted the main and had a nice downwind run to St. Maarten. Arriving in Simpson Bay (Red Star on the map below) we turned into the north anchorage where we furled the jib used the main to tack back and forth a few times until we spotted a sufficient slot between two boats on the leeward end of the anchorage.  We scooted into our spot, turned upwind, dropped the main, stopped where we wanted, dropped the anchor, and had enough wind to push us back and set the anchor.  Who needs an engine?!?    

 

We assumed the repair would take at least a week and we were overdue for a marina stay, so I found a marina with great amenities (Yellow Star, below). They had one slip available at a great price, so we reserved it for two weeks - check it out.

When I told Guy Ciletti, the marina manager, that we were without propulsion, he offered to bring his 14-ft boat out, lash it to Cayuga's hip, and act as a tug to get us to the marina.  My plan had been to use that same setup with our own dinghy, but Guy had 100 HP compared to our 15 HP, so accepting his offer was a no-brainer.  All went well as we passed through one of two drawbridges at 11:30 am (Red Circle, above).  We timed our course to arrive at the next drawbridge for its scheduled opening at noon (Red "NOT" sign, above). We started circling when the bridge didn't open on schedule, and then the bridge tender announced on the radio that he had lost power and had no idea when the bridge would open again.  Really?  Guy said that had never happened before, so it must have been our bad-luck cloud. So we dropped anchor and Guy went on to his other afternoon commitments.  However, the power company showed up and electricity was back on at the bridge in time for it's scheduled 3:30 opening, Guy returned, and we joined forces again to continue on to the marina. 

I was initially afraid that the boat would have to be hauled in order to separate the prop shaft from the transmission in order to pull it and get to the damaged part.  CAYUGA's engine is installed "backwards", with a V-drive transmission and prop shaft running through the transmission and aft under the engine.  But my diesel expert in Annapolis explained by phone that I could pull it apart with the prop shaft in place.   

 

By the time we settled in there, I had gathered enough information to have the confidence to tackle the repair myself.  I'll spare you the blow-by-blow -- suffice to say that the dis-assembly was a long day's work. The damper plate was a mess -- see the old and new damper plates in the next photo. Good thing it's generally made of soft metal or it could have broken flywheel gear teeth.  Since I started the engine a few times since the catastrophic failure and didn't notice any problems, I assumed the teeth were still intact. The Yanmar dealer in the far eastern end of the lagoon didn't have either a new or used damper plate in stock, but he told me to check with the Volvo dealer on the French side because some Volvo installations use the same part.  So I took my old plate to the Volvo guys (who only spoke French) and they all shook their heads, "Non".  After communicating that the Yanmar guy said that it was a part used by both manufacturers, they looked more closely and began to nod "Oui".  One guy disappeared into the back and returned with a used plate that exactly matched mine and was in excellent condition.  The manager looked on his computer and said, "cash or credit card?", and I said, "Depends on how much..."  He said, "New is $500".  "Non, non", says I, with my best shocked face mask.  "The new Yanmar part is available on the Internet for $200, and the Yanmar dealer here can get one for me for around $300."  All true. I offered my opinion that a good used part should cost no more that half the new price and offered $150 cash. He accepted.

At that point, we're only three days into the repair process and, as they say in the Haynes car repair manuals, "...re-fitting is simply the reversal of removal...".  So I figured one more day would see it all back together again.  But I hadn't counted on the difficulty of positioning a 40-lb transmission in a confined space such that the shaft splines were perfectly aligned and would engage.  I solved that problem with a spider web of line to support the transmission, and with Rhoda turning the engine crankshaft back and forth with a wrench, the splines/transmission/engine finally struck the sweet spot of alignment and slipped together. Putting everything else back together, cleaning the bilge and tools, and doing an engine oil change for good measure wound up taking a couple of days.  But it's done now and a test at the dock indicates that all is well.  In the end, it really could have been a whole lot worse, and have happened in a much less convenient location.

 

With this little adventure behind us, I can add my voice to the chorus of cruising sailors who claim that the real definition of cruising is "...doing boat maintenance in exotic places...".  

 

Our next destination is Antigua, so maybe there we'll get to patch a hole in the dinghy, sew a ripped sail, or something else equally exciting...  However, until then, we're making the most of this unplanned diversion, taking time off from repairs and professional work for walks on the beach, laying by the pool, and some good food and drink. And making friends with other folks in the marina.  

 

 

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