Seaflo Raw Water Strainer - Improvement?

[sveinung]

Our raw water strainer clogged yesterday limiting the flow enough to raise the coolant temperature a bit before we noticed.
Since it's above the waterline with a clear top of was a straight forward inspection and fix, but i was surprised to find just how little debris was needed to limit the flow.
Our old below-waterline filter didn't clog a single time, even when having a lot of debris in the basket.

The seaflo seems to run fairly empty, just with some water covering the inlet and outlet, wouldn't both the flow be better, and filter be a lot less prone to clogging if the filter was full of water?
I can "prime" it by closing the seacock and filling it with water, but i was wondering if i could do this easier by raising the inlet tube inside the strainer a few inches?
That way i could fill it without closing the seacock, and if it ever sucked air, it wouldn't siphon back out.
And more water in strainer means debris will be more spread out and not clog.

Is there a consideration I'm missing? I was going to test this by just putting a piece of flexible tube into the inlet hole to raise it.

Black dots are debris:

[tkeithlu]

I've got two concerns here. The first is why the filter is above the waterline, and the second is why the filter is in the circuit to begin with.

As long as you have this plastic item above the waterline, you have the opportunity to suck air - any small leak will do. I would not entrust my engine's cooling to anything plastic between the seacock and the engine's raw water pump, in any case.

In my boat raw water for all uses comes in from a slotted strainer under the hull. It's there to keep large fish and small SCUBA divers out of the cooling system. Above the seacock is a strainer with a very large number of 1/4 inch or so holes. That keeps small fish and gravel out of the pump. The connection to the pump is 1 1/2" wire reinforced hose with double hose clamps. All the hard stuff is bronze. The whole thing is very robust. It's all below the water line. Your system sounds delicate by comparision.

What about junk in the pump? First off, the through hull is located out of the way of mud and sand. Hard aground, there is still about two feet of keel below the strainer. Second, I carry spare impellers for the raw water pump. After over 1,000 hours and I-hate-to-think how many groundings, I have not yet replaced the impeller. For that matter, neither have I clogged the heat exchanger.

I hope that you will give some serious thought to your cooling system. You don't mention your engine type or size, but even in a quite small engine I would expect a stouter system with better assurance of continuous flow.

[Sailmonkey]

Those plastic strainers are quite common, but if you’re loosing water flow from blocking only the bottom of the basket, it may be the design of the seaflo is flawed, seeing as its a cheap copy of the Vetus strainer.

Also, found this little tidbit on an Amazon listing for a seaflo strainer

[sveinung]

Originally Posted by Sailmonkey

Those plastic strainers are quite common, but if you’re loosing water flow from blocking only the bottom of the basket, it may be the design of the seaflo is flawed, seeing as its a cheap copy of the Vetus strainer.

Also, found this little tidbit on an Amazon listing for a seaflo strainer

Attachment 234095

Interesting, that's exactly what I had in mind! I'll look into Vetus, the seaflo was very cheap, but it seals really well even after a few years. A generic o ring would be the only wear piece.

Yes, I'm not particularly concerned about the safety of this setup. Less hose clamps and failure points under the waterline is good in my book, and better access to inspect and clear is good as well.
Having the motor run warm is also cheaper than lifting the boat off the ocean floor.

[sveinung]

Vetus had a few different models, both seemed better than the Seaflo one I have.
The FTR140 has exactly the design i suggested, where the inlet is raised 3/4 to the top of the chamber or so.

Their other line it's raised slightly, so you get the benefit of using the entire surface area of the basket, instead of just what's above the outlet.

We have some 1500 miles on the Seaflo, so I'd say it's still a good value, just like the design of this better, although 3x the price at $80.

[stormalong]

I would replace it with a Groco ARG series strainer. It has a removable basket strainer and is much better made than the Vetus. It is safe to mount it at or below the water line. Mine is about 6" below the waterline.

There are other things that the strainer is there to catch, like grass and assorted man made debris. My ARG strainer can get a lot of grass in it before flow is restricted. The screen basket allows more water flow than the little holes in plastic strainers.

Yes, it cost more but it will last the life of the boat.

You might also consider audible overheat and/or water flow alarms if you don't have one. A gauge is not enough protection unless you watch it almost continuously. A serious overheat can do a lot of damage to the engine. Running the impeller dry can destroy it, leaving you disabled until you can replace it.

[SV__Grace]

We have two of these made by Vetus just inside our engine room door, a smaller one for the generator and a larger one for the engine.

I appreciate them being above the waterline so I can easily and quickly open them and clean the strainer. I have a slotted wrench mounted next to them to easily remove the caps if needed.

Their location makes it easy for me to do my engine checks- I can check the strainer, bilge, fuel filter bowls and vacuum gauges, etc. quickly and at a glance before embarking and while underway.

I've never had to prime them, even after the boat has been out of the water.

When underway, if we pass through an area with a lot of debris, especially floating seagrass, I check the strainer often while underway, but rarely suck up other stuff unless the engine or generator is running at anchor or in the harbor. Did get a small fish the other day.

[sveinung]

Originally Posted by SV__Grace

We have two of these made by Vetus just inside our engine room door, a smaller one for the generator and a larger one for the engine.

I appreciate them being above the waterline so I can easily and quickly open them and clean the strainer. I have a slotted wrench mounted next to them to easily remove the caps if needed.

Their location makes it easy for me to do my engine checks- I can check the strainer, bilge, fuel filter bowls and vacuum gauges, etc. quickly and at a glance before embarking and while underway.

I've never had to prime them, even after the boat has been out of the water.

When underway, if we pass through an area with a lot of debris, especially floating seagrass, I check the strainer often while underway, but rarely suck up other stuff unless the engine or generator is running at anchor or in the harbor. Did get a small fish the other day.

Nice! I'm excited to test this Vetus one, seems like a better design, hopefully arrives one of the next days!

Originally Posted by stormalong

I would replace it with a Groco ARG series strainer. It has a removable basket strainer and is much better made than the Vetus. It is safe to mount it at or below the water line. Mine is about 6" below the waterline...

The Groco ARG style strainer is exactly what I removed 2 years ago, to get it above waterline.

[SV__Grace]

Originally Posted by sveinung

Nice! I'm excited to test this Vetus one, seems like a better design, hopefully arrives one of the next days!.

Just be sure it's sized for the engine, I can imagine having problems with one that is too small or too big.

My 85 hp engine strainer is 5" diameter and the 5.5 kWh generator is 3" diameter (from it's size I would estimate 20hp).

Hose size might be a clue as well.

[oztayls]

Originally Posted by sveinung

Our raw water strainer clogged yesterday limiting the flow enough to raise the coolant temperature a bit before we noticed.
Since it's above the waterline with a clear top of was a straight forward inspection and fix, but i was surprised to find just how little debris was needed to limit the flow.
Our old below-waterline filter didn't clog a single time, even when having a lot of debris in the basket.

The seaflo seems to run fairly empty, just with some water covering the inlet and outlet, wouldn't both the flow be better, and filter be a lot less prone to clogging if the filter was full of water?
I can "prime" it by closing the seacock and filling it with water, but i was wondering if i could do this easier by raising the inlet tube inside the strainer a few inches?
That way i could fill it without closing the seacock, and if it ever sucked air, it wouldn't siphon back out.
And more water in strainer means debris will be more spread out and not clog.

Is there a consideration I'm missing? I was going to test this by just putting a piece of flexible tube into the inlet hole to raise it.

Black dots are debris:

Looking at the design of the Seaflow strainer, it appears to me that you need to prime it so that the water level is at the top with minimal airspace. That head space is essential for proper operation as the water needs to churn. A bubble of air is all that is needed. I'm sure that if you did that, it would not clog so readily.

I have a Vetus Type 330 in mine, a similar design to the Seaflow, and it is currently below the water line. I must say that this disturbs me a bit, as if a hose on it springs a leak....well, enuff said, it's the stuff of nightmares, even though Vetus say is can be mounted below the waterline. I will be raising it above the waterline shortly and installing new hoses. The best thing to do is close the seacock every time you leave the boat unattended. That is good practice anyway. Then when you open the seacock next time you use the boat, it's a simple matter to check the strainer.