Do these screws go all the way through?

[The Continuum]

Hey everyone. I went to test the bilge pumps in a boat I just got, and neither of them worked (died from old age). I am about to install two new ones, but I have a question about the screws into the bottom of the bilge floor. I have not removed the old pump bottoms just yet. I’m a bit nervous that the when I unscrew them, water will start shooting in at me!

My question is about the hull. Is it a single layer of fiberglass, or is a double layer with a hollow space in between? In other words, do those screws go all the way through, or only part way into the fiberglass.

On my 1997 290 Sundancer, do you think that the hull is like picture #1? Or is it like #2?

The exact location is between the two engines, almost all the way back at the transom wall. The two pumps are screwed down between two raised shelves that the engines are mounted to.

Thanks for any advice!

 

[Southpaw II]

Picture 1. Just use the same length screws when you go back with the new pumps.

 

[Lazy Daze]

I'm not sure on the hull structure. But, I am positive that water will not "shoot up" at you.

However, you may be able to get new pumps that are a direct replacement - meaning they can be installed into the old brackets/bottoms (if they are of that style of design).

If you put it new bottoms - using different holes - be sure to fill the old holes with silicone.

 

[tobnpr]

Easy way to tell if you're dealing with a "false bottom". Your hull has a "V" shape. If the pumps are mounted to a flat-horizontal surface, it's not the hull bottom.

I have never seen a boat builder put self tapping screws into the bottom of a hull- for anything. Not something you'd ever want to do.

Seacocks, etc. that are mounted directly to the hull bottom have epoxied or glassed-in wood backing blocks for the screws.

Be sure to use a good sealant on the screws.

 

[The Continuum]

Thanks for the info. Lots to learn!

Luckily, I found replacement pumps (Rule 1000’s). The new pump tops could snap into the existing bottoms, so I did not have to remove and install new screws.

-Seth

 

[fwebster]

The answer is neither of your sketches. The construction is as tobnpr says for a horizontal surface and in some cases Sea Ray laminates a wood block into the hull for mounting components. Always dry the area well with a shop vac then just replace the existing screws in the same holes using 3M 5200 and there is no risk of perforating the hull bottom.

 

[The Continuum]

Makes sense. Thank you!