intake strainer (1st time poster)

[ybrad]

Greetings all, first time posting here-


Recently I acquired a 1980 37’Cutter; good bones, but a definite project boat. On the hard currently and plan to have the basics done to splash her in the next month or two. Long slow process after that with the vessel eventually out on a mooring.
Many questions to follow.

Great site, what a resource! Thanks in advance for input.

o The raw water intake hull strainer for engine cooling (Yanmar 3QM30H) is oriented with the slit openings facing forward, hence it is a scoop. Raw water pump impeller resistance as the means to prevent drowning the engine while under sail (engine not running) or remembering to close the seacock (much less open it) seems lame, but this configuration appears to have made it so far.
Should the strainer be reversed/modified so the intake side faces aft (so as not to back-flood the engine)?

 

[Rich Stidger]

I have always understood that the scoop should face aft so as not to pressurize the engine. However, if the pump has a good impeller, I would be very surprised to have water get past it with the pressure from sailing. A street-pressure garden hose would be quite a different matter.

I think you are OK. Others will chime in if I am wrong.

 

[Jeff]

ybrad,
I suspect if you turn the exterior strainer around a vacuum of sorts
could be created. It may impeed the circulation somewhat. I new
impellar each year is a good idea though. Leave well enough alone
and move to the next project on your list.

Jeff

 

[kloudie1]

Quick note, mine has been slits forward since before I owned the boat, 17 years now. I will change to slits aft if I have to pull it for any reason. I understand slits aft reduces fouling in the fresh water intake.

 

[Guest]

Engine through hull

Based on the opinions thus far, I would contact Hunter Marine Customer Service and ask them for their recommendation. I'm trying to remember how ours is oriented, but alas my memory fails me, although I think our louvers are vertical, so orientation matters little.

At your hull speed I doubt whether high or low water pressure at the intake has any meaningful effect. The primary purpose of the louvers is to help keep eel grass, fish and other substances from entering or blocking the cooling system.

Terry Cox

 

[ybrad]

Thanks for the inputs. Unless a convincing reason surfaces between now and splash, as-is is what will be. Plenty to do on the project list.

 

[Paul F]

Sea water strainer

If your boat does not have a sea water strainer between the intake and the raw water pump you might consider adding one. It provides a way to filter the water going into the engine cooling system. If you add one don't over strain/filter the water as my first strainer did. The alge blooms in the summer time plugged the unit. After going to a larger gage strainer the problem has not reappeared.