Engine cooling through hull question

[Eli27]

I am gonna change out the through hull for the engine cooling water. It seems to have a standard through hull. My question, should i put a standard through hull in there or get the fitting with high speed scoop?

The boat is a 1979 Albin 36 with a single leyman 120hp. Now i plan to go super fast with this boat just so ya know lol.

My opinion is to leave it the same. I cant see how Max speed of 11knots can make that much difference. I know the boat wont see 9 but im factoring in some serious current.

Thanks for all responses.
Eli

 

[Comodave]

No need for a scoop at your speed. Put in a proper through hull and seacock. I believe Steve D has an article on his website about that.

 

[Eli27]

No need for a scoop at your speed. Put in a proper through hull and seacock. I believe Steve D has an article on his website about that.

Thats my opinion too. I could see going it going above 15 20 and bouncing above the waves. I can see how you could possibly air lock it too. But 10 knots,,,,, yeah i dont think so.

Thanks
Eli

 

[Comodave]

You need to make sure the through hull threads and the seacock threads are the same and will fully engage. A lot of boat builders use NPT and NPS together and they don’t engage very well. Also use a proper seacock and backing plate inside and through bolt the seacock to the hull, don’t depend on the through hull threads to hold the seacock on.

 

[jleonard]

I changed mine and added a scoop on my 40 Albin/ Lehman 120. Helps filter out eel grass etc. I’m also went up n size to 1 1/2 inch.
Also the oem thru hull was something I had never seen before. It had a beveled body. I had to do some fiberglass work to fill it then drill a new hole for the new one.

 

[Eli27]

You need to make sure the through hull threads and the seacock threads are the same and will fully engage. A lot of boat builders use NPT and NPS together and they don’t engage very well. Also use a proper seacock and backing plate inside and through bolt the seacock to the hull, don’t depend on the through hull threads to hold the seacock on.

I know what you are talking about with the seacock. Groco makes the 3 holed seacock. My question to that is do i bolt it all the way through to the outside? I cant remember seeing that in all the yards ive been in. I know its a newer thing.

And yes, i know to put a backing plate in there.

 

[Comodave]

Yes, use bronze flat head bolts and countersink the holes. Through bolt the seacock and then screw the through hull in and it will cover the bolt heads on the seacock.

 

[Bacchus]

I haven't done this but my go to is compass marine for boat DIY.
He has an article on proper thru hull installation.
Bolts go thru backing plate but not thru the hull.

https://marinehowto.com/seacock-backing-plates/

 

[Eli27]

I haven't done this but my go to is compass marine for boat DIY.
He has an article on proper thru hull installation.
Bolts go thru backing plate but not thru the hull.

https://marinehowto.com/seacock-backing-plates/

I like how he says he doesnt use the method for his own but should be good enough. Not word for word but basically.

 

[PM]

You don't need a scoop but an exterior strainer might be a good idea.

Your boat will cruise at about 5.5 kn. at around 2,000 rpm. I tell people that to go any faster in y boat I will have to run it over a waterfall.

pete

 

[Fish53]

You don't need a scoop but an exterior strainer might be a good idea.

Your boat will cruise at about 5.5 kn. at around 2,000 rpm. I tell people that to go any faster in y boat I will have to run it over a waterfall.

pete

I agree there's no need for a scoop however I also don't believe an exterior strainer is needed either. I have a Perko strainer inside and have only once had anything limit flow. All I need to do if it clogs on the outside is remove the hose to the seacock raise it above the waterline, open the seacock and shove a short section of mop handle down through to clear it.

 

[jgwinks]

You don't need a scoop but an exterior strainer might be a good idea.

Your boat will cruise at about 5.5 kn. at around 2,000 rpm. I tell people that to go any faster in y boat I will have to run it over a waterfall.

pete

Some people don't like external strainers. They can get clogged up with barnacles or on fresh water with zebra mussels. And being on the outside they're not easy to clean. But I have them and find that things like seaweed or small fish bounce off the screen and I hardly ever get anything in the internal strainers. But being in Michigan I get to clean them out every winter when we haul out. The people who don't like them are probably in salt water and rarely haul.

 

[psneeld]

I agree there's no need for a scoop however I also don't believe an exterior strainer is needed either. I have a Perko strainer inside and have only once had anything limit flow. All I need to do if it clogs on the outside is remove the hose to the seacock raise it above the waterline, open the seacock and shove a short section of mop handle down through to clear it.

Those are my thoughts to Capt.

On the assistance tow boat I ran, I would run that aground or though inches of water and slime about 10X a day on busy weekends.

I had 2 seacocks on opposite sides of the keel that I could hook the inside strainer to. One had a exterior screen, the other didn't.

I would swap back and forth depending which one had the best flow at the time and if needed, I could be ramrodding the non-screened one while I idled along on the clogged screen one. Once cleared I would switch and resume normal ops ...back in deep water it was easy.

Had several hundred hours over 13 years logged on that 454 gasser with the high temp alarm going off, but never had to stop and let it cool so I could get a customer home in a jif.

 

[rgano]

Regarding exterior scoops, I run at 16 MPH anytime the engine isn't warming up or coming off plane to moor or anchor and have no problem getting sufficient cooling water.