Generator blowing bubbles

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Sep 7, 2022
My generator is blowing bubbles out of the sea water inlet. No exhaust is coming out of the exhaust outlet on the side of the boat.
I recently changed the generator out, because the old one was worn out and did not start. I had been cranking on the old one numerous times, to no avail.
The new generator wants to run, but will not start. Injectors have been bled. Filters changed.
If I have flooded the muffler, how do I get it cleared, so the generator will run? I suspect that excessive back pressure is what is causing it to not run.
Stop everything. You see air coming out the water intake? Who did this installation?
Is the engine rotating backwards? There should be an arrow.
Can you pull the exhaust hose off the elbow, assuming it’s above water level?
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The muffler should have a drain plug or valve. I use a valve closed by exhaust pressure that opens when the engine is stopped.
You may have hydro-locked the engine. Shut off the raw water intake and pull an injector. Look into the cylinder. If there’s water, get help asap.
It seems like the exhaust is blocked
Group reply

Thank you all. I found the problem. I used a big shop vac to simulate exhaust flow. Nothing was passing from the mixer elbow to the outlet on the side of the hull. I broke the exhaust system into sections and tested for flow. I discovered that the aluminum elbow at the inlet to the muffler was clogged with corrosion and salt crystals.
I bought the boat a year ago. It had sat in the slip for over six years. Before that, it was used extensively in salt water.
I cleaned out the elbow, and reassembled the exhaust, after vacuuming out the system. Went through the starting sequence. It fired up and ran like a champ!


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Is this blockage responsible for the failure of the previous genset?
a prudent new genset install should come with all new intake and exhaust systems. IMO
I bought the genset used. The owner had removed it from his sailboat, and had it serviced by Western Branch Diesel.
The old generator was worn out. Almost no compression. And the valves all needed replacing as well. The first layer of metal on the valve faces was worn away.

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