Missing 3.7L Alpha One Gen 1 Water Shutter Valve

[GarySequim]

I pulled my boat out to run it in the driveway for the first time this year. It started fine and water was exiting the stern drive as it should. And then a giant white cloud blew out of the exhaust, unaccompanied by water. Steam, I hope. I quickly shut it down and pushed the boat back into the garage.

I pulled the stern drive apart and found that the nearly new water pump and impeller were still fine and there was no debris in the water passages. I then pulled the exhaust elbow and found no water shutter valve, only the metal rod that used to hold it.

Sooo ... I rented a fancy bore scope and checked the exhaust from inside and outside the boat. I could find no trace of the missing shutter valve. I hope this means a previous owner took out any pieces and forgot to install a new shutter. But, I wonder if the pieces somehow got forced up the exhaust into the manifold? This seems unlikely; I just hate to put everything back together and find I missed something.

My next step is to trace the flow of sea water to see if I can find a blockage. It seems like the boat's problem should be the missing shutter valve, but it couldn't have disintegrated in a few seconds when I fired up the motor in the driveway.

Ideas for how to further troubleshoot this will be gladly accepted. Should you ever need help with a 105 series Alfa Romeo, I can help. Otherwise, I'm pretty much useless. Oh, not entirely useless. I've attached a copy of the sterndrive repair manual I put together for my own use, as all the others are disorganized or leave out stuff that's important for amateurs like me.

 

[dubs283]

When you split the drive did you remove the drive from the bellhousing and split, or leave the upper attached and just drop the gear case?
Asking because the shutter/flapper could be stuck in the exhaust bellows or the exhaust passage between the bell housing and upper portion of the drive

 

[nola mike]

I pulled my boat out to run it in the driveway for the first time this year. It started fine and water was exiting the stern drive as it should. And then a giant white cloud blew out of the exhaust, unaccompanied by water. Steam, I hope. I quickly shut it down and pushed the boat back into the garage.

I pulled the stern drive apart and found that the nearly new water pump and impeller were still fine and there was no debris in the water passages. I then pulled the exhaust elbow and found no water shutter valve, only the metal rod that used to hold it.

Sooo ... I rented a fancy bore scope and checked the exhaust from inside and outside the boat. I could find no trace of the missing shutter valve. I hope this means a previous owner took out any pieces and forgot to install a new shutter. But, I wonder if the pieces somehow got forced up the exhaust into the manifold? This seems unlikely; I just hate to put everything back together and find I missed something.

My next step is to trace the flow of sea water to see if I can find a blockage. It seems like the boat's problem should be the missing shutter valve, but it couldn't have disintegrated in a few seconds when I fired up the motor in the driveway.

Ideas for how to further troubleshoot this will be gladly accepted. Should you ever need help with a 105 series Alfa Romeo, I can help. Otherwise, I'm pretty much useless. Oh, not entirely useless. I've attached a copy of the sterndrive repair manual I put together for my own use, as all the others are disorganized or leave out stuff that's important for amateurs like me.

Don't know if your overheat is the cause or effect of your shutters burning up. Love the guide, I'm going to save it. Saw you put part numbers in some places, as well as torques. I'd love to have a list of common torque values that I can never remember (outdrive, prop, steering pin nut, etc) in one place in the beginning. I always mean to write it down, but am covered in grease when I need to do it...

 

[Bondo]

Ayuh,.... Welcome Aboard,..... Likely places to find shutter debris is, at the bottom of the down pipe, in the exhaust passage in the lower unit, inside the prop, 'n I've seen 'em shot right out through the prop,....