Tag Archives: Yanmar 3GM30

Crispy, Hard and Smoking. pt.2

Launching a boat is a process couched in optimism. The annual ritual of unwrapping, polishing, swapping fluids and slapping on bottom paint leads to a triumphal splash that marks the beginning of another sailing season.

This year I was somewhat organized but left starting the motor until the last minute. I wasn’t too concerned as my Yanmar 3GM30 has always fired up easily. This year, it was already in the water when it finally started…. but I’m getting ahead of the story.
Tortuga was already sitting by the crane when I arrived an hour ahead of my scheduled launch time. Uli was unusually efficient that morning and the crew were itching to launch. So much for a leisurely pre-splash inspection. I grabbed a pail of lake water and scrambled onboard to start the motor while the slings were being fitted. It seemed that the battery was weak as the cranking rpm was low and the motor wasn’t catching. Strange… Complicating the starting process was the crane’s diesel motor was idling six feet from my head. I think roaring is a more apt description as I couldn’t hear the engine cranking and was relying on the tachometer to see if the engine was actually turning over. This really threw me as the batteries should be, and were, fully charged by the solar panels. This was confirmed by the voltage showing. I’ve never started the engine deaf, relying solely on the tach, so I wasn’t sure how fast it usually spins on startup.

Rather than delay the launch any longer, I gave the go-ahead to splash. I figured this would give me time to charge the batteries and figure out what was going on. I set the charge controller to equalize to get a deep charge. I let it sit for an hour. I finally got the engine to start and immediately there was a smoke coming from the engine! A quick shutdown and inspection revealed that the alt was seized?! Now I’m completely confused as the alt was fine at haulout and recently rebuilt! The boat is dry and the water fresh so corrosion shouldn’t be a factor. I loosened the belt and then loosened the alternator pivot bolt – this freed up the alt.

In a flash, all my confusion vanished and all the sensory feedback made sense. The alt mounting arms have 1.5mm of play on the engine mount, I must have tightened up the alt and that warped the housing enough to pinch the rotor. Luckily releasing the pressure released the pinch and no real damage was done.

I shimmed the gap with a washer (will have to get the proper diameter) and replaced the belt with a new Gates AX 37 TRI-POWER, keeping the old lightly toasted belt as a backup.
I hope I haven’t over-stressed the poor starter motor, I am actually surprised and impressed that I was able to start with a seized alt, not something that I want to repeat.

 

Lessons learned

  • I should have started the engine at least the day before in the quiet of the yard. Being in a rush and feeling pressured to meet the yard schedule isn’t the best path to clear thinking.
  • I should have stopped cranking and inspected the engine, although catching a seized alt is hard to notice, stopping and thinking might have led to my remembering that in the fall I adjusted the belts and must have tightened the alt mount with more vigor than previously.
  • I should trust what I know. I knew the batteries were charged, I could see the voltage was high and the starter battery cable was warm to the touch. This should have registered in my brain that the cranking loads were high and something was amiss.