Blower fan going, going, ...

[Tony Benoit]

Hello,

When I got my '89 Mk I, the PO had disconnected the blower fan.  I had always assumed that it was dead.  But I am trying to reduce the oil smell aboard, so I found the old wires and jumped them to 12 volts.  The fan roared to life.

I just spent the evening rewiring the fan.  (And I did a lovely job if I do say so myself--A DPDT switch in the instrument panel lets me run it either off the ignition circuit with the key on or off the house circuit with the key off.)  I ran the fan to burn in the installation.  Both circuits worked fine.  After a momentary surge of about 5.5 Amps, the fan drew 3.7 A.  But after about 20 minutes the blower motor started making a lot of noise, as if the bearings were going.  (And current draw was creeping up--4.1 A.)  My guess now is that when the fan heats up the bearings go wonky, and that's why the PO disconnected it. 

Has anyone replaced that fan?  Any suggestions for a source?

Thanks,

Tony

[Stu Jackson]

Tony, WM usually has a pretty good "catalog" of just about everything made for boats, so I check their catalog out first and then comparison shop (usually elsewhere).  Pretty standard "blower" or engine compartment fans, and are usually ignition protected because the fan motor can also be used in gasoline engine compartments. Since you just rewired it, you should know exactly what it looks like.

[Tony Benoit]

Hi,

I followed Stu's advice and started with WM.  After reviewing that catalog I went to Defender and bought a Rule Model 140 that has low current draw and moves a lot of air.  After I performed some lazarette gymnastics I managed to install it. 

The fan runs great, but boy is it noisy!

Has anyone found a quieter blower motor or some way to keep this one quieter?

Thanks,

Tony

[Tony Benoit]

More on the new blower motor:

If I unscrew the fan from the wooden plate underneath the coaming and let it hang from the vent hose, there is very little noise, just the whoosh of air.  So, it appears that most of the noise is being transmitted through the fan housing into the hull.

I put some neoprene washers under the mounting feet of the fan, and that helped, but it is still pretty noisy.  The vibration might be being transmitted through the mounting screws.  I might try isolating the screws using rubber grommets, but I would need to drill out the holes in the fan. 

What would seem necessary is an intermediate plate between the fan and the boat.  I could bolt (or wire tie) the fan to the plate and screw the plate to the boat.  I am trying to think of a material that would be hard enough to support the fan, but soft enough to damp the vibration.  Note that the fan is fairly light.

I could wire tie the fan to the heavy reinforced hose that runs from the deck plate to the fuel tank.  No doubt that would be a simple and effective short-term solution.  But I would worry about the possibility of shaking loose the fuel hose in the long run.

Any thoughts?

Thanks,

Tony
Helen C/#903
Std/Wing

[Ken Juul]

I don't like the wire/spot tie idea either.  You might want to try a "sandwich" the motor between rubber washers to isolate the vibrations.  I think the thicker the washer the better.  Will probably need a steel washer between the nut and the rubber one to prevent it from pulling through.