Question about raw water cooling arrangement

[Luhrs28]

Hi Guys:

I'm putting a GM 6.2 diesel V8 engine in my old Luhrs cabin cruiser, and I'm wondering if I have the right plan of attack on my raw water system. The order of components I have in mind is:

- Raw water in through scoop-strainer thru-hull (1.25")
- Strainer (1.25")
- Sherwood G7 pump (standard rubber impeller type), 1.25" size
- V-drive jacket
- Tranny oil cooler (mini heat exchanger)
- Engine oil cooler (mini heat exchanger)
- Main heat exchanger
- Y-splitter, with 1/2 flow going to starboard manifold/riser and 1/2 going to port manifold/riser

What I'm worried about is, each component in series after the pump has some pressure drop/restriction. Is my Sherwood pump going to be able to pump enough flow through all that stuff?

Is what I've described a pretty normal setup?

What I'm thinking is, at idle or low speed the cooling demand is very low (especially with a diesel engine). At high speeds the cooling demand is high, but also water will be forced into the scoop pickup which should boost the pump's efficiency quite a bit. (like supercharging the pump) Right?

Thanks,

Bert

 

[Greg Mrozinski]

Re: Question about raw water cooling arrangement

Bert,

Sounds like a normal V-8 FWC set-up to me. The amount of raw water should be fine. You might want to check the cooloing capacity of the heat exchnger you plan to use and see if it is big enough to handle the demand of the diesel cooling cycle.

 

[Luhrs28]

Re: Question about raw water cooling arrangement

Thanks Greg. Actually I don't have the heat exchanger yet..........one of the last expensive parts I still have to buy. I will research the capacity needed.

Thanks again for reviewing my plan.

Bert

 

[Greg Mrozinski]

Re: Question about raw water cooling arrangement

You might be able to get away with the standard big block gas engine exchanger. I don't know how much hotter the diesel will run compared to the gas engine.

 

[sasto]

Re: Question about raw water cooling arrangement

On a Cabo with 6cyl Cats I have 3 inch connections to a Sherwood pump and no seastrainer. We need plenty of water flow to keep the engine cool and also the exhaust with lift mufflers. I would think you will need exhaust elbows custom made and covered in the area where the raw water meets the exhaust.

Then again, I'm no engineer. You appear to always have your bases covered.


I need to edit: that cooling system is on our 12 cyl Mans, and they are Johnsons. 1.5 inch on the 6cyls. they are shurwood.

 

[Luhrs28]

Re: Question about raw water cooling arrangement

Thanks Sasto. I think I'm going to be OK with the 1.25" plumbing, because A) my engine doesn't have a turbo, and B) It has relatively low output (154HP) for the size of the engine (379 cu. in). Many of the Cats and Cummins are putting out close to 1 HP per cubic inch of engine displacement.

Still, as a little insurance I think I'm going to go with a big heat exchanger. It can't hurt. (well it'll hurt my wallet but that's OK).

Thanks for your input.

Bert