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Old 03-09-2012, 08:08   #1
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Keel Cooling Help Needed

Hi Folks

I have twin 6-354 Perkins diesels with Walter V-Drives in my new-to-me, but older, 40 foot steel trawler which has never seen salt water.
That is going to change in 2014.

My questions are: Can someone help me with designing Keel Coolers
(of the 1" to 1&1/5" Pipe size for both - engines and v-drives. I don't have any info on volumes of cooling fluid needed for either unit to provide adequate cooling. I don't want to run salt water through this machinery.

What are your thoughts on 3 blade verse 4 blade propellers? My boat
has 3 blade props on it now ( 24 x 20's) ,
and it came with 4 blade (24 x20) spares. Can someone tell me which
would be more economical to operate?
What are your thoughts on the pros and cons of each?
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Old 03-09-2012, 08:32   #2
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Re: Keel Cooling Help Needed

Capt Nemo:

Post your question on boatdiesel.com. There are some real pros on that forum who deal with commercial boats and can give you some rule of thumb design advice for keel coolers.

Three blade props are more efficient than four blade ones but sometimes have more vibration.

David
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Old 03-09-2012, 14:25   #3
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Re: Keel Cooling Help Needed

Quote:
Originally Posted by Capt Nemo View Post
My questions are: Can someone help me with designing Keel Coolers
(of the 1" to 1&1/5" Pipe size for both - engines and v-drives. I don't have any info on volumes of cooling fluid needed for either unit to provide adequate cooling. I don't want to run salt water through this machinery.

What are your thoughts on 3 blade verse 4 blade propellers? My boat
has 3 blade props on it now ( 24 x 20's) ,
and it came with 4 blade (24 x20) spares. Can someone tell me which
would be more economical to operate?
What are your thoughts on the pros and cons of each?
First.. It's nothing to do with volume, it's the surface area/hp. I don't recall the how much but can check it up next weekend.
Second.. Generally 3 bladed is more efficient than 4 bladed but it depends.. No way to tell without more insight in your setup.
BR Teddy
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Old 03-09-2012, 14:47   #4
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Re: Keel Cooling Help Needed

The Metal Boat Society might be a better place to post.
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Old 04-09-2012, 11:44   #5
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Re: Keel Cooling Help Needed

Why not just convert to eat exchangers designed for the engines. Most probably cost about the same or less and a lot easier to install. Just my two cents, Mike.

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Old 07-09-2012, 00:08   #6
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Re: Keel Cooling Help Needed

Ok.. Your engine should have about 115hp. Dave Gerr says 25mm round copper tube 23.5cm/bhp so it means about 25m tube for single engine. That's for free running under 8 kn, seawater <85F or 30C. One inch tube is quite small so it needs to be paralled (maybe 4 tubes, just a quess? but a bit more than the area of the original coolant tubing) to avoid excess flow velocity and counter pressure. The flow speed should be btw 2 to 8ft/sec or 2.5 to 0.6 m/s. Chec the specs of the coolant pump!
BR Teddy
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