Undersized Strainer? - SailNet Community
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post #1 of 10 Old 12-09-2012 Thread Starter
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Undersized Strainer?

I brought my Perko sea water engine intake strainer home for the winter to clean up and rebuild. Before I get too far into doing that, I noticed that it's a 1/2" pipe thread model while my 2GM20F's raw water pump intake is 5/8". This setup has presumably been in place for 8 years with no known adverse effects on the engine. Is there any reason for me at this point to upgrade it to larger model or should I just look at is as ain't broke/don't fix things?

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post #2 of 10 Old 12-10-2012
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Re: Undersized Strainer?

Is the hose from the stop ****/ thru hull to the strainer also 1/2 inch or is it 5/8 also?

Is their reduction barb for the 5/8 hose from the water strainer to the pump? or is it just a threaded NPT or not threadded 1/2 inch fitting with a 5/8 inch hose on it clamped tight?

What is the size of the hose from the pump to the engine?

I bet the strainer was added on after the OE. If it was me I would have it all the same size? Check out Bcons, Ill bet they have the correct size laying aorund in that back room/


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post #3 of 10 Old 12-10-2012
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Re: Undersized Strainer?

I have a 1/2 inch thru-hull/strainer/et cetera on my 2gm20 (raw-water cooled) and it seems to move plenty of water. These little engines don't need a whole lot of cooling water flow to keep them happy. If you have never had any problems with overheating don't sweat it.

Never forget them. Do something to prevent it from happening again.
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post #4 of 10 Old 12-10-2012
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Re: Undersized Strainer?

I have a 1/2 inch intake on my Yanmar 3gm30 and even when motoring in the very warm water in the Brazilian summer, it delivers enough water to keep the engine cool. If you've been using your strainer with no problems, I can't see why you'd need to change it.

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post #5 of 10 Old 12-10-2012
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Re: Undersized Strainer?

Your Lip30 probably has the typical Oberdorfer raw water pump that supplies 3-4 gallons per min. at 2000-2500 engine rpm.
Such ~approx. 30hp marine engines whether raw cooled or FW/Hx cooled are designed around this 3-4 gallons per minute flow ..... OUT THE EXHAUST when at YOUR 'customary' max. rpm (not 'wide open throttle' rpm)

AND ....

..... With a bucket (of known volume - gallons) and a stop watch, etc. simply validate/check if you are getting ~3-4 gallons per minute (.75 - 1 gallons / 15 seconds, etc.) into the bucket at the 'exhaust overboard' outlet .... while the engine is spinning at YOUR customary max. cruise rpm.

If yes, all is OK 'as is',
If not, change the pump 'impeller', then check again, and if still not ----- change to a strainer with larger 'nozzles', change out ALL that 1/2"ě hose to larger while youre 'at it'.

The correct 'service design' size ě is: the internal diameter of the hose that is between between the raw water pump and the inlet to the exhaust manifold .... use this diameter as your 'guide' for all hose, etc. diameter in the entire raw water 'loop'.

1/2"ě nozzles at 3-4 gallon per min. flow will have about 4 times the 'pressure drop' (and less flow) than 5/8"ě nozzles. 1/2"ě would be 'marginal' for such an installation, the stopwatch and bucket will verify with a 'clean' / unfouled strainer .... but you do need 'reserve capacity' for operating when that strainer becomes partly fouled.

;-)
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Last edited by RichH; 12-10-2012 at 03:30 PM.
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post #6 of 10 Old 12-10-2012 Thread Starter
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Re: Undersized Strainer?

The thru-hull is 3/4" with a 3/4" hose attached. The elbow going into the strainer steps it down from 3/4" to 1/2" by way of a bunch of fittings screwed together. The outlet of the strainer has a 1/2" barb with a 5/8ö hose clamped down on it going to the raw water pump (it was badly corroded and I plan to replace it). 5/8 is the correct size for the RW pump.

I have a feeling the strainer is a remnant from when the boat had a smaller raw water cooled engine and didn't get changed out when the PO repowered.

I may try the test Rich suggests in the spring or I may just upgrade to a 3/4" strainer now while I have everything out and apart. Thanks for the suggestions all.

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Re: Undersized Strainer?

Check out Bacons,,,no sense in a new one.


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post #8 of 10 Old 12-11-2012
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Re: Undersized Strainer?

Bacons doesn't typically have engine related parts do they? Worth a check I guess. I'm using a Groco Groco ARG-S Series Raw Water Strainer with the new engine, I didn't find them that pricey all things considered.
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post #9 of 10 Old 12-11-2012
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Re: Undersized Strainer?

The easiest way to break something is to touch it.

You can quote me on that.

Lessons learned are opportunities earned.
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Re: Undersized Strainer?

Quote:
Originally Posted by chucklesR View Post
The easiest way to break something is to touch it.

You can quote me on that.
You said to quote you!
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