Marine raw water to closed system. What to do?

[lars11]

Thinking of converting my marine v8 from 1999 to closed cooling system. I want to prolong its life and also improve operating conditions. But I suppose there are some rust in the engine by now. Should I do something special about it except for flushing thoroughly? Use a cooling system cleaner? Which one, for how long? Etc etc...
Any ideas to make this switch as efficient as possible considering the situation?

 

[Volvohead]

Lars, past a certain point (especially in salt or brackish), it's probably not a good idea to convert over to FWC. The typical RWC setup presents relatively low system pressures. FWC will be a standard pressurized system - a sustained 12 to 15 psi in most setups. If you have enough internal corrosion, areas near gaskets and seals may be eroded. The integrity of the gasketing and seal systems may not handle the added pressure. You could have leaks springing out anywhere. A place like an exhaust riser gasket is not a place you ever want a leak starting.

It will depend on a close look at how much has already been eaten up by the seawater. You'll be opening up the mainfold-riser joint anyway if you convert, and that is where I would take a very close look for existing corrosion.

But if it's in good shape, I would just run repeated flushes and change out the coolant early the first couple of seasons. Buy a new set of draincocks, as you'll be opening them quite a bit during that time.

 

[lars11]

ok. I changed the manifolds and elbows this year so they are new. The exhausts will not be pressurized, just the block, as I am thinking of a half system. I see your point and the main areas for concern for me would then be the head gasket interfaces. I think that maybe if there will be a leak in the head, the engine is toast anyway soon. In that case I can move the freshwater kit on the new block...

 

[Volvohead]

If you've already replaced the manifolds and elbows, you should do a full FWC system if you do one at all. Those parts are the ones that benefit the most from what FWC has to offer. Engine blocks and heads are relatively hardy. The wall thickness in a manifold cooling jacket can be as thin as 1/8 inch at the gasket location. That 1/8 inch of gasket is ALL that separates the seawater from the cylinders, and there's hot exhaust gasses flowing on the other side. It's a lousy design and no wonder it's the biggest marine engine killer.

 

[wapacz]

Yeah pretty much i can't bring much to this as I just found it interesting and have never seen one of these systems set up. Since I live in Michigan where all we have is fresh water and a climate limiting the use of a boat to half the year, which routinely leads to 70 and 80s boats with the original engine in them.


I guess for others it may be nice to know which engine you have and what boat it is in. Also if it is fresh or saltwater.

 

[lars11]

yep, it's a 1999 Regal 258 with a volvo penta V8 5.0Gi and a DP-S outdrive.

 

[Volvohead]

I've done several FWC conversions over the years. It's a day job if you loaf it. Mostly plumbing, but some gasketing changes are required. If not done right it can create more problems than it solves. The best kits are as good as OEM. It's also best to do it early in an engine's life. Whether to do it later depends on what it's been sitting in.

FWC benefits engines in any climate, but sharply so in salt water, where it can add years to components. Makes winterization a lot easier, too, as the jackets are already full of antifreeze. But it does require more maintenance on the whole and can complicate doing other engine service. The systems do take up extra space. And they don't eliminate the need for outdrive ears for yard starts.

 

[lars11]

I am looking at a Monitor FWC system. Temps in Sweden are low and leaving water in the block for winter is a certain block-cracker. That has never happened to me but I am always worried about it, since it can be difficult to know if all water is really out. Thinking of flushing with antifreeze but that is quite expesive too over time...
Some say that you achieve better running conditions with a FWC system due to more uniform and slightly higher op temps. Is that true? Anyone noted better running engines?