New Project

Since the end of last year the motor has been harder and harder to start.  I chased a fuel air leak for a couple of months and once that was solved I came to the conclusion that we were suffering from low compression making a cold start difficult.  The Yanmar 1GM10 is not a complicated diesel  motor but I have no familiarity with it.  So with lots of research and talking to people I decided to try to fix the low compression my self.  Low compression comes from a leaking valve, bad head gasket or blow by in the cylinder.  Usually the later but I tried the valves and head first.  I removed the cylinder head, did a valve job and re installed with a new gasket.  The valves were tight and there was no leakage from the top end.  However, there was a lot more blow by in the bottom end.  Conclusion: Engine needs to be pulled from boat and rebuilt.

Front

Right Side

Having gained confidence from the head job, I decided I can do this rebuild my self.  However, pulling the motor out of the boat for a couple of months was advised against in case I have to move the boat out of the marina during a hurricane.  And the cessation of any sailing activity over the summer lead me to pursue another route.  I located an old used motor, age and condition unknown.  I negotiated a price and picked up a summer project this past weekend.  I will document the rebuild here with lots of picture and my inevitable mistakes for the world to see.  Or at least me and the 3 followers of this blog.

Left Side

Rear

 These pictures were taken after pressure washing and initial cleanup.  I then began tearing apart all the hoses, wires, etc to see what we had.  The starter was cracked and shot, needing replacement.  The alternator was frozen, needs replacement.  The motor will turn over by hand which indicates low compression.  Thermostat frozen, internal zinc, gone.  Transmission seems to engage in forward and reverse.  I soaked the transmission coupling  and was able to separate the old shaft.  Everything was coming off nicely until It came time to remove the transmission.  The eight bolts came out fine and the bell housing separated from the engine.  It will not come any further.  My manual says it should slide right off.  The input shaft should come out of the clutch plate splines with out any tricks.  I can not budge it.  There is evidence of rust (sever) on the fly wheel and clutch plate.  The shaft seems to be frozen in rust.  I am currently applying pressure and soaking in penetrate to see if it will give..

Carbon build up on exhaust mixing outlet

Underside of cylinder head showing valves

In the mean time I have removed the head.  Valves are as to be expected and piston looks OK.  I will try to use a micrometer to get bore gauges and see what condition he cylinder wall is in and if it needs honing or a re-bore. Once I get the transmission off I can asses the extent of the shafts and if I need new bearings etc. Included with the motor was also the control panel and associated wiring harness and the lift wet muffler.