Mystery block

[bananaboater]

I have a block of synthetic material (inboard) through which the screws that attach my speed sensor protrude. I cannot determine if it is some sort of insulating material or just an unnecessary spacer. Anybody have any clue?

Thanks, Albert

 

[arks]

Re: Mystery block

Looks like a phenolic block.
Here's a description:
Phenolics, hard and dense plastics, are produced by the application of heat and pressure to layers of cotton fabric. When heat and pressure are applied to the layers, a chemical reaction transforms the layers into a solid mass. These materials are extremely versatile because of their unusual combination of properties. They are lightweight, dense, structurally strong, resistant to moisture, and will not soften appreciably under the application of heat. Its high impact strength is great for mechanical applications such as gears, pulleys, insulators, washers and rollers.

 

[bananaboater]

Re: Mystery block

That's it.

Now do I need to keep it? I am about to redo the unit and am curious if it is critical to the function.

Albert

 

[legoman67]

Re: Mystery block

its probably plugging some form of hole, looks like there is sealer around it, maybe the PO changed the pito pickup and had to take care of a hole.... looks overkill though...

 

[erikgreen]

Re: Mystery block

My guess would be that it's a backing plate, basically a strong way to attach those bolts and prevent them from pulling through or cracking the transom.

Probably that type of plastic was used because it was waterproof material. It may cover a hole or help seal against water coming in around the bolts, or not.

Definitely something added by a previous owner, not the factory. Remove and replace at will.

Erik

 

[bananaboater]

Re: Mystery block

Thanks, you have confirmed my suspicion, re not critical, but did not come up with the fact it might be covering up big hole.

Albert

 

[system-f]

Re: Mystery block

You can replace it with Derlin if it is not already Delrin. We have tons in our machine shop and the marine uses are endless. Some people use them to bring their swim platform up higher for when their boat is filled with ballast.

 

[mkast]

Re: Mystery block

Thanks, you have confirmed my suspicion, re not critical, but did not come up with the fact it might be covering up big hole.

If the speedometer sensor was mounted without the block, over time, the mounting holes through the hull would be cracked or enlarged. It's not covering up a big hole.
Standard mounting for distribution of stress.

 

[bananaboater]

Re: Mystery block

I've got some 1/2 inch teflon I will use.

 

[ezmobee]

Re: Mystery block

My bet is it's covering like 12 holes from previous sensor/transducer/etc mountings

 

[bananaboater]

Re: Mystery block

Got around to removing the block, no problem and just 2 holes.

Next question is how does this speedometer work? It has an air line that feeds a long thin cylinder inside the boat. I know they are not very accurate but I would like to keep it and hope it works.

One big ? Is this supposed to spring out of way if it hits something? It looks like it may have a spring loaded system inside the external mount. If so how do I help it get back it's function?

Thanks, Albert

 

[Fisherball]

Re: Mystery block

It's called a pitot tube. It works by vacuum. As the tube goes through the water, it sucks air from the tube. How much determines how fast the speedo reads. They are inaccurate unless the water is completely still. If you are moving with a 5 mph current they'll be 5 mph off. They are also used on airplanes. As long as the plastic tubing has no holes there isn't much to break or wear out. Your speedo itself may not work. Check the hose for leaks or cracks b/4 you replace your speedo. The pitot is an inexpensive item.