adding freshwater cooling to stern drive: doable? and what advantages?

[driscollies]

Hi tpenfield,

thanks for the information. And thanks for clarifying: I had thought that one had to put on different risers in order to have the correct fittings.... but I guess I have no idea what I'm talking about!

So if (big if) two systems have heat exchangers with similar capacities, they are pretty easy to swap out for one another? My big issue was dropping 1200 on a system that a) may be useless because my engine is so old, and b) may not even be necessary because I'm going to be in bays and flushing it every time. If I can get a decent system for 50 bucks, that'd be well worth it.

Or, I guess, the other option is to just buy the proper heat exchanger on ebay. Spending a little more, but may be worth it. I see them for 100-300 dollars?

The one thing I'm worried about is the fittings. Are these things I can just pick up somewhere, or are they model specific?

thank you so much

 

[HT32BSX115]

From what I'm gathering, these kits are mostly heat exchanger and tubes, with specialized risers and such. How difficult is it to convert from one mercruiser cooling system to a different mercruiser cooling system? There is someone near me who is selling a closed cooling system for $50 because they're parting out their boat, but they say theirs is for an "inline six" mercruiser with a pre-alpha outdrive. I have a BBC. Is it worth spending to 50 bucks essentially to get the heat exchanger, and then planning on spending more on the risers and stuff?

The risers are no different. There is however a riser block-off gasket/plate that (for FULL systems only) prevent coolant from getting into the risers. (raw water only there since that's where it exits the boat)

Using a heat exchanger for a smaller engine could result in an overheat since a BBC will reject far more heat than a SBC or inlne six(in that order) . (HP = HEAT ....... ref: General Physics)

That heat has to be transferred to the lake water via the heat exchanger. They're very efficient. Far more efficient than a water-air heat exchanger (automotive radiator)

In a boat, they size them for the engine size (HP) ...........so an exchanger for a 496 might be physically larger than one for an 4-banger or inline six. They are also dependent on raw water flow [rate] through them........ which is why an alpha raw pump might not cut it, requiring you to go to a Bravo or similar size (external engine driven) raw water pump.

That heat exchanger might possibly be physically the same size as a BB exchanger. if it is, you'll still need a MUCH larger raw water pump to move enough water through it. Especially if you want to cool the manifolds (full system) if you just want to do the block (1/2-system) , you reduce the heat load quite a bit, but you'll still have raw water flowing through your manifolds. I would want a full system.

One of the common leak points for any engine is the riser gaskets. (open or closed systems) If you have an engine that can use "Dry-Joint" manifolds and risers, you eliminate that possibility of leak for ever, Because there is NO exit for water at the riser-manifold bolt points. Water is routed around the actual flange via a hose.

Unfortunately, there are no "dry-joints" for the 454/ 7.4L engines (They are available for the 350 series and 496.)

 

[driscollies]

thank you so much for the information.

I hope I'm not being too dense, but maybe I can clarify what I think you're saying... I'm gathering that you're saying that the components of a freshwater system are the heat exchanger, hoses, and fittings. The hoses are just regular hoses, but the heat exchanger is engine-specific. So it's probably not a great idea to go with a different heat exchanger from a different engine unless I can actually verify that the flow rate, size, etc. are all exactly the same. However, if I can find a used heat exchanger that is actually made for my engine, I should be able to put the rest of the cooling system together just based on parts from my local auto parts store, with the exception of things like gaskets, which I'd want to special order from a marine parts warehouse and should be bought new anyways.

Is that pretty accurate?

thanks again!

 

[tpenfield]

I think you just have to flip a coin as to going forward or not. There is nothing to say that a used heat exchanger will be trouble free. Usually the troubled ones become 'used'.

Bay = Ocean . . . so there is no comfort in the different bodies of water.

Flushing helps, but there is something about salt that finds its way. Not sure if there are any studies of comparative images of engine blocks that were salt vs salt/flushed vs fresh water vs coolant only

 

[jimmwaller]

Also curious about this. Considering a used heat exchanger.

That being said, I also have an i/o that has been used in a bay but flushed.... maybe we can throw together our own study! Anyone have a i/o that's been used in salt and not flushed?

 

[driscollies]

yeah so thank you for the advice so far. Did a flip and I'm gonna get a used system and hope it lasts just a little longer than my engine, haha.

So if I get the proper heat exchanger, I will be able to put together the rest of the system from parts from west marine or autozone or something? Like, the heat exchanger is the only "odd" part in the kit, the rest of it is universal?

I also have an old pre-alpha outdrive of some kind that came with the boat. The owner said that I can convert between the two easily. I think I'm going to save my nicer alpha drive, put on the older drive for now, and then go with a used system. Full, if I can.

And then I just buy gaskets from a marine parts warehouse?

Is that it? Seems simple. But I guess that makes sense if the big cost of the system is the heat exchanger. Just want to make sure that if I buy the right exchanger, I can actually make a system out of it without too much hassle or expense.

thank you

 

[Aussieguy55]

..
I've spent this years budget on rebuilding the transom and the motor but I want to put in a FWC system to protect the new motor
so used is my only option for a season or two.

buying a used heat exchanger tips
Take some tools with you .... adjustable wrench, remove the end caps of the exchanger

look inside for any previous repairs... blocked off tubes
if more than 20% are blocked off ..... REJECT

a simple PRE purchase test ...
block off all the "coolant" side fittings .... A couple of well placed thumbs can work as corks take a friend with you have extra thumbs/corks! ,
fill the coolant side with water as much as you can
you may have to tilt the unit if can't plug up all the holes .... just o make sure the water is covering the end plate
watch the holes in the raw water side if any water comes out the unit is leaking
repeat the test on the other end

if you don't see any obvious leaks consider purchasing and taking it to a radiator repair shop to be thoroughly cleaned, inspected and pressure tested

if there is a leak BUT no previous tubes blocked off ... the unit may be able to be repaired

I just bought one for $20.00 it was advertised for $150.00, I was able to prove to the seller it was leaking!
if it can't be repaired... I can probably get most of my money back selling it as scrap metal.

in Florida we don't get a a lot of freeze damaged exchangers... leaks are more than likely due to corrosion of the brazed / soldered joints
radiator shops can repair heat exchangers.. but most of them just simply and quickly block of any tube that is leaking
slower and more expensive fix, is to have the ends of the tubes re-soldeed / brazed.


am trying an experiment with 3 leaky exchangers.... Epoxy fix
large commercial heat exchanges have been repaired for many years using epoxy

I have worked with epoxy in construction.. even helped develop an epoxy timber joint system that holds up entire commercial buildings (No nails, bolts or screws!)

If and when I do this will add a write up ..

NEW EXCHANGERS.... Tip:
when I can afford to buy a new one .... I am going to epoxy coat the RAW water side where all the tubes have been soldered/brazed
will block off all tubes with a temporary plastic plugs , don't want the inside of the tubes getting epoxy
paint on a couple of coats of high temp JB weld , remove temp plugs
You could .... take the unit to a powder coater and get them to coat the raw water side.. make sure they use epoxy thermo set powder

should extend the life by a huge degree.
I'm sure the manufactures could /should do this but like most things built today, they are built to be replaced.

PS.... never use the 5 minute epxox!