DIY Fresh Water Cooling??

[jmb23802]

I have been kicking around the idea of putting a freshwater cooling system on the Volvo Penta 5.7 gxi-d engine in my boat. This is a lake boat so I would be happy enough with a 1/2 system (block only) for now. Kits for the "d" version of this engine seem harder to find than some of the other submodels, not sure if it is just a limited production submodel or if there are design issues that preclude the use of a closed cooling system on this engine. I also don't like the price tag of the kits that are roughly $1,500 - $1,800 just for the kit components, and those are not even close to the price of the Volvo kits! So, I would like to explore the idea a bit here and see what the experts say.

I like the idea of a closed cooling system for a couple reasons: potentially higher operating temps for the engine - running at 180 or 190 vs. the 160 thermostat it has now, which would be closer to the operating temp the GM engine was designed for. Also, theoretical improvements in engine longevity via reduced corrosion and scale inside the block coupled with somewhat simpler winterization efforts.

I have a few questions, and looking for advice from anyone in-the-know about fresh water cooling kits (1/2 system).

1. Is this project as simple as buying a used heat exchanger tube designed for a 5.7L MPI (Volvo or Mercruiser), a burp tank, and routing new hoses? I know I would need to fabricate some way to mount the heat exchanger tube somewhere. What else would I need parts-wise? Seems like I would need to either replace the t-stat housing or block off the hose ports on the t-stat housing that currently go to the exhaust manifolds.
2. Would I see any benefit (or detriments) to putting a higher thermostat in the engine to get it closer to the GM-designed operating temp without a re-program of the ECM? Should I stay with the 160-degree thermostat if I choose not to pursue any ECM programming changes?
3. If I ran the engine at a hotter operating temp would I need to change to a cooler spark plug?
4. Routing: I think my hose routing for the raw water side would be such that the raw water would pull through the outdrive, up through the impeller on the crank-mounted pump, and into the inlet side of the heat exchanger. The raw water outlet flow side of the exchanger would then "Y" to the exhaust manifolds so the raw water would cool the manifolds and risers and exit through the exhaust pipe like it would in a typical raw water cooling system. Please poke holes in this approach.
5. The routing for the closed cooling side would go as follows: the return line off the circulation pump would feed the inlet tube on the heat exchanger. The outlet tube on the heat exchanger would flow to the thermostat housing. Please poke holes in this approach.
6. What coolant would I use - ethylene glycol (the green stuff) or propylene glycol (i.e. Dex-Cool)? The engine is a 2003 based on the GM Vortec engines - so seems it would readily accept propylene glycol but not sure if it would be better to go with the old green stuff since I am pretty sure this is a cast iron block and heads.

So, am I dramatically over-simplifying this or is it truly this simple? If I am on the right track, it seems I could pick up a used heat exchanger on ebay, get some hoses and clamps from the auto parts store, and add a 50/50 coolant mix to the block.

 

[Scott Danforth]

the D is the last year of the run. first year A, etc.

Volvo only offered half systems until the cat motors

you have to reprogram to go to HX cooling to allow the motor to know why its now running over 140 degrees. no way around reprogramming

if the motor is more than a few years old, you may have issues going to a HX. the crud sitting in the water passages normally plugs up the HX. that crud is sand, rocks, shells, etc. and rust flakes. to truly clean out the water passages, you need to pull the motor, pull the heads and mechanically clean the passages. (I have used 1/4" cable chucked up in the chordless drill)

or start with a fresh long block.

with a 17 year old motor, I would run it until it needs a replacment block, then add HX cooling to the new motor.

just my 2 cents coming from a guy that designed and sold HX's to Mercruiser and VP

 

[cptbill]

I agree with Scott if you need to repower that would be the time, my 2 cents for what it's worth I don't see any real advantage to closed cooling system on a fresh water lake, if you were doing salt water then yeah

 

[Bondo]

Ayuh,..... In #5, yer lookin' at the flow Backwards,......

'n I agree, wait til yer droppin' in a new or reman motor,.....

The crap in yer's will clog the side of the exchanger ya can't clean,.....

 

[jmb23802]

Well, it looks like the consensus is that the heat exchanger will get clogged with gunk accumulation in the engine. That had crossed my mind, but didn't think it would be that big of a deal after a couple of flushes. The engine is 17 years old, but only has 250 hours and posted good compression numbers at the end of the season last year. I pulled the exhaust risers (appear to be original) this Spring and everything looked quite clean in there. But, I have no doubt there is some crud in the block right now, rust scale if nothing else, that could potentially impede the function of the heat exchanger sooner or later.

I appreciate the help. I'll heed the advice here and stick with the raw water system.

 

[Scott Danforth]

in fresh water, your exhaust manifolds and elbows will last decades

just as and FYI - the last fresh water SBC I pulled apart to upgrade to vortec heads. I pulled about 4# of sand and rocks from the block water jacket that did not come out with flushing (that is when I use the cable in the drill with the motor upside down on the stand)

I have even found baby clam shells in the block water passages. so at one point the outdrive was sucking lots of mud

with only 250 hours in 17 years, you need to use the boat more often. that is two days a year of boating use.

 

[jmb23802]

in fresh water, your exhaust manifolds and elbows will last decades

just as and FYI - the last fresh water SBC I pulled apart to upgrade to vortec heads. I pulled about 4# of sand and rocks from the block water jacket

with only 250 hours in 17 years, you need to use the boat more often. that is two days a year of boating use.

4# of sand is impressive.

I agree about the hours; I picked this boat up at the end of the season last year and intend to improve that average.