R25 Through Hull Strainer

[chrispangaro]

Hello

I have a 2008 R25 and it has a through hull with strainer. In warm Australian waters this furs up with marine growth too readily and reduces flow to the engine excessively. I would like to get rid of the strainer that is attached to or part of the through hull. However, the boat lives permanently in the water, i have no trailer, and its lifted about once every eighteen months and only for two days then for antifouling/anodes.

Can anyone tell me whether the external strainer is integral with the through hull or a separate screw on plate that attaches to the external of the through hull? Not that keen with limited time and assistance to completely remove and replace the through hull if its integral. Alternative plan i had was to simply cut/grind off the grating of the strainer so its open - that way i can also work antifouling up into it. Thoughts on this course of action welcome!

Thanks

Chris

 

[Matty]

I cannot imagine cutting it to remove the protective strainer would be good given what could happen if you suck something in.
I did look to see there are several youtube videos on how to replace. Several while boat is in the water. If you watch a few you just might see the one in you have in your vessel. Seems to me you would want to be on a sand bar if things go wrong.
Anybody nearby that has a boatlift that can let you use it?
Good luck!

P.s. not sure what your tides are like but might be able to have a low tide help you. Still scares me a bit.

 

[captstu]

Our R25 had an integral thru Hull strainer.

We removed it and replaced the thru Hull, valve and sea chest with a setup that removed the strainer, valve and elbow.

It is all documented with lots of photos on the boat’s web site. Look around

Shearwater-sailing.com




Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[TexasEye]

Can the strainer be "Backwashed" with a HP Water Hose? And would this improve the flow?

 

[dclagett]

The clam shell strainer is part of the thru hull. The strainer is held in place by the nut on the thru hull inside the boat and 2 screws into the hull on the outside of the boat. This is a job for the boat being out of the water.

One thing you might try is to get a stiff pole with adjustable length and extra stiff bristle brush attached to the pole. I have been able to clean my thru hulls from the swim platform using this arrangement. With the engine hatch up you can measure the distance and angle to the thru hull from the swim platform. You will be able to feel the thru hulls as the brush moves over them.

In my album I have pictures of my solution to your problem. I am sure there are many other solutions others may suggest.

 

[Salty7]

Rather than grind the entire strainer off you might consider cutting every other slat out of it. This will make it easier to clean, produce more raw water flow yet still able to do some straining. The only other option is to replace it with one with a removable screen. It isn't the best design and it is marginal in terms of volume of water able to pass through it even when clean in it's original form. If you decide to replace it I would go at least one size up.

 

[captstu]

Before I removed the strainer and replaced it with a proper through hole, I went under the boat with a screwdriver and snorkel and was able to easily bend and break all of the strainer fins.

That was not enough to cure the overheating problem on our 4BY2.

You can clearly see why removing the fins does little good. Visit the Boats website.

Shearwater-sailing.com

Look at the photographs, you will see that the transition from the fin area to the threaded inlet section is too small to admit enough water to cool the engine once build up of marine growth takes place. This transition area also effectively stops you from cleaning the through hole by reaching down from the top.

This through hole is a poor design and is destined to fail in areas of high growth.


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[chrispangaro]

Thanks for the feedback all. Will certainly cut off the screen bars on the thru hull but given your useful pics Stu may have to plan on complete removal and replacement with a conventional thru hull. Poor design indeed. In current heatwave conditions here marine growth is extreme and in less than a week weed is growing sufficient to cover the inlet. So regular snorkel under to give it a scrape out but its not a workable solution long term.

Thanks again

Chris

 

[captstu]

When I changed the thru hull to a "proper" design, the temperature dropped from overheat alarm to 198 degrees at WOT.

Proper, to me, means a straight-thru design with no elbow. On the Shearwater, the thru-hull has the valve directly above and the strainer directly above that - with the water line, at rest, being about 1/4" above the lip of the strainer. When the cap is removed and the strainer basket removed, you can see directly down the strainer, thru the open valve, and thru the thru-hull out into the water. I carry a threaded 1/4" rod that can be inserted thru the open strainer down the "stack" and out into the water below - removing 100% of the growth and crap should the engine heat.

If you look at the photos, I also added a flow switch and an exhaust overheat sensor to detect low flow from a failed/failing impeller.

It makes no sense to omit these safety features in a boat like ours - impellers fail for no apparent reason, age, crap, whatever - why not detect and prevent further damage.