I kept putting this project off because my engine was running ok and of course I kept hearing, 'If it ain't broke don't fix it,' but I never really felt comfortable that my engine would keep running when I needed it the most. So in December of 2006 between races I pulled out my tools and decided to see what was going on inside. It turns out that because of a botched rebuild two owners ago it really was time to rebuild.
The original plan was to just replace the head gasket as it was leaking a bit of oil and while the head was off I would get the valves done. The compression in cylinders 2 and 3 were about 15% low and there was a little extra blow-by in the crank case. After the machine shop discovered the head was in very questionable shape and had been crack repaired (not a good idea for marine use) I decided to replace the head.
Though the valve seats weren't in the best shape they probably didn't account for all of the compression loss and since I was invested in a new head I decided to really jump in and drop the oil pan, pull the pistons, and replace the rings & connecting rod bearings. Good thing that I did because, as it turned out, pistons 2 & 3 had their connecting rod caps mixed and their bearings were in bad shape... nearing end of life. I replaced the pitted piston, and installed all new rod bearings (top & bottom), wrist pins, and rings.
Fortunately the Universal/Westerbeke M25-XP is a repackaged tractor engine, the Kubota D950, so I could get most of the parts from a tractor supply for less than 1/3 of the price. Here are some photos that tell a bit of the story... or, if you've ever wondered what the inside of your engine looks like, here you go.
Started with low compression in cylinders 2 & 3
Valve Cover, Rocker Arms & Manifold Removed
Head Off, Trouble in Cylinder 2
Pitting in the Head and had been Crack Repaired on Exhaust Valve Seat
Pistons 1 & 3 looked OK
How far will this go?
Misc parts removed
Leaking Sea Water Pump
Salt Dripping on Engine from Leaking Pump
Piston Parts (replaced 2,3,7,9)
Cut Away View
Mixed Rod Caps on Pistons 2 & 3. Whoever rebuilt this before was lucky it ran at all.
Connecting Rod Bearing Damage, Needed Replacing
Rod #1 Bearing was better
Cylinder Liners Look Good
Crank Looks Ok
Crank Looks Good
Carl Stirtz Machine Shop, Oakland CA
Carl Stirtz Machine Shop
New Head (note cap on pre-chamber)
Rebuilt Sea Water Pump
Ready for the Pistons
Pistons Going Back in with Correct Rod Caps
First Coat of ($30/can Westerbeke) Paint
Head Gasket in Place
Head Back On
18 Bolts on the Oil Pan
Just enough room to install the pan
Injectors & Valves Ready to Go
Sea Water Pump going back on with Globe Run-Dry Impellor
Back Together & Ready to Run
Compression tests show it's back to the factory spec, 450psi!