Volvo Penta 5.7 Gxi - Salt water

[AirStage]

Hi everyone,

I recently purchased a Cobalt 255 with a 2005 Volvo Penta 5.7 GXi engine and would like to use it in saltwater. I was wondering if I should modify the cooling system. At the moment, it’s an open cooling system. I’ve searched this forum and the internet for info and kits to convert it to a half-closed system.

I have a few questions I couldn't immediately find answers to using the search function:

• Is it necessary to modify the cooling system for longer periods in saltwater? (The boat will be in the water for about 6 months.)

• Would using a NeutraSalt system be an effective solution instead?

• I also read something about a "boat bag," but couldn’t find any concrete information about it.

A boat lift would obviously be ideal, but that’s not currently within budget.

Any tips or advice are very welcome!

Thanks in advance.

[jhnmdahl]

I would seriously consider changing to a closed loop cooling system if economically feasible. There are other things like anode material, bottom paint, etc., that can also make a difference in saltwater that aren't common concerns for those of us who mainly boat in fresh water. A good marina or service center near where you boat may also have some good advice, as they deal with this kind of thing all the time.

[AirStage]

Thanks for the helpful info, this also aligns with my own preference. I’m seriously considering converting to a half-closed cooling system.

I’m currently looking for a good quality conversion kit. Does anyone have experience with a reliable kit (ideally one specific to this engine), or can recommend a trusted supplier?

I also read that flushing or cleaning the engine block prior to the conversion can be quite difficult after long-term use with an open cooling system, which may lead to reduced cooling efficiency and higher temperatures. Any advice or tips on that would be greatly appreciated as well. The boat has spent the last 20 years in fresh water.

I did read somewhere that the GXi series — and possibly the GXi-F in particular — was originally designed with saltwater use in mind. If that’s true, am I perhaps overthinking the need for a closed cooling conversion? I'd love to hear if anyone has insight into how well these engines actually hold up in saltwater over time.

Lastly, can anyone recommend good service manuals or technical documentation for this engine? Preferably something detailed enough to help with the conversion and ongoing maintenance.

Thanks in advance!

[bruceb58]

An engine that is 20 years old may not be a good candidate to convert to closed cooling. Even if the boat has been in fresh water all its life, there may be enough corrosion to keep you from doing it.

Call these guys and see what they have to say.

https://orcamarine.com/

[AirStage]

Just a quick update – I’ve reached out to Orca Marine via email to ask about the availability of a closed cooling conversion kit for the 5.7 GXi and to get their advice on the feasibility for an older engine.

Thanks again to everyone for the helpful input! I’ll share any useful info I receive from them here in case it can help others in a similar situation.

[Kate]

". . . use it in saltwater."

For saltwater use, there are also special procedures and products for cleaning and protecting the interior and exterior. Cobalt offered a saltwater package, aka the "Coastal Edition." But I seriously doubt your boat has it.