Cobaltchat.com

Hi,

Buying a 293 with 2 Volvo Penta 5.7 GXI that has always been in fresh water. The cooling system uses some raw water and I have been told that in order to use it in salt water I may need to convert to a closed cooling engine system.

Does anybody have any experience with this? How costly is this conversion?

I have the price to paint the bottom and change the anodes

It's not too bad if you are doing a half system which doesn't cover the manifolds.

When you say your system uses some raw water, does that mean you are already a half system?

Call these guys
https://orcamarine.com/

'Need' is not necessarily accurate, you can decide what additional protection it affords, depending on what your configuration/investment might be.

As Bruce suggests, there are essentially three classes of water cooling:
1. All Raw water (sourced externally from wherever the boat is used, whether this be 'fresh' lake water or ocean brine) - this system is going to cool everything, including the engine galleries and the exhaust manifolds/risers. There are a LOT of boats being in used in Salt Water that are going to be this config. Ideally, the system is flushed with fresh water whenever the boat is pulled out of the water.
2. A half system - this employs a closed loop cooling system for the Engine, somewhat like your car - except instead of a radiator, it uses a water to water heat exchanger where the 'sea' (sic) water removes the heat from the coolant; so you have the sea water pump which circulates that external water supply and a second water pump on the engine coolant system. The Manifolds/Risers are still going to be cooled by the Raw Water.
3. A Full System - cools everything, including the manifolds/riser in a closed loop system

Most kits that are either factory installed or retrofit, are going to be half systems, which still leaves exposure for the Manifolds/Risers. So recognize if you add these kits it's about $2500 or so per motor to give you that capability. Incidentally a replacement Manifold/Riser kit runs about $1000 (more for taller risers) which is not as bad as might be expected.

My VP 8.1 boat is used predominantly in sea-water but has NO closed loop cooling. This model engine was designated OSi however, as their 'Ocean Series', specifically for use in Brine.

One great feature of the Ocean Series XDP drive is a revolutionary structural composite that provides exceptional impact protection, lower weight, greater fuel economy and a hydrodynamic profile with 10% less drive drag. Onboard oil reservoir, integrated trim function and power steering are standard. This design also requires fewer parts for increased reliability and provides increased exhaust area for reduced backpressure and improved engine performance.

Equipped with a standard fresh water flush port, Ocean Series models feature Volvo Penta’s exclusive Neutra-Salt Engine Flushing System as standard equipment. Corrosion resistance is further enhanced through the use of stainless steel fasteners, coated oil pans and EDP treated exhaust manifolds and risers.

I'm not sure how much added protection there is on the 'treated' manifolds, however the semi-automated Neutra Salt system* is IMO a valuable asset.

What this comprises, is a reservoir tank that holds the Neutra Salt plumbed via a Solenoid Valve into the Water Intake Line; so at the end of the day, you operate the Solenoid for 30-45 secs before shutting off the engine, which disperses the Neutra Salt throughout the Cooling System to mitigate the corrosive effect of the Salt Water.
(* See here for a test on its effectiveness)

Now that system would be quite easily retrofit and be beneficial even if you already have (or intend to add) a half system retrofit. It's additional protection for the exposed system, especially if your engine can't be flushed immediately after use for the day.

Great info!

On my last boat that I used in salt water, I put in a Neutra salt system. I would operate it before i put it on the trailer as I pulled out of the water and also at the end of my fresh water flush so the engine and manifolds would have the solution on them while the boat was sitting on the trailer.

Yes, that's pretty much exactly what I do Bruce.
There are occasions when I might leave the boat on the Buoy overnight and so fresh water flush not possible; and especially for that situtaion the NeutraSalt system is invaluable.

Anyone can actually install one of these on pretty much any boat really
There is a kit available from VP (good price here at Leaders)
But you can probably put this kit together yourself for a fraction of the cost.
Should be a fairly easy retrofit, probably the most challenging aspect would be in mounting the switch and running the wores back to the Solenoid
The image below shows the kit parts and you will see there is nothing particularly special - but some might not mind paying the extra for Brand recognition, perhaps with respect to Boat resale at some point

Thank you everyone. @ Commander Decosse, that was a naval engineer explanation that the mundane and simple beginners like me can still understand. Thank you very much!! Great info!

Thank you @NorthForkers - that was very gracious.

A Post Script - I just did my Winterization this weekend - as Part of that process I flush with RV Anti-Freeze (the pink stuff) leaving the residual in the system. Now I wanted to add a Neutra Salt injection as the AF was depleting (as per a normal end-of-cycle stage, even though it had been injected at the last fresh water flush immediately following last shutdown and had not been exposed to new salt solution) - but simultaneously ALSO apply fogging oil just prior to engine shut off.
i.e. It needed to still be running the Coolant through the system AND inject NS AND Apply Fogging oil immediately prior to killing motor.
I began to attempt this and quickly realized not enough hands for one person!
So I reset, refilled the Flushing Reservoir with more AF but this time adding some NS directly into the flushing res; then with about a Gallon left, started the Fogging - Mission Accomplished, I was left with a residual mix of AntiFreeze and NeutraSalt in the system along with Fogging Oil through the Intakes.

FYI - this is the Flushing Reservoir Kit I use -