Full system cooling

[joeyleggz]

Does anyone know if it is possible to convert a half freshwater cooling system to a full freshwater cooling system on a 7.4 L EFi MerCruiser with the current set up?


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[joeyleggz]

Bump


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[kap2]

CP Performance offers a full system http://www.cpperformance.com/c-1527-complete-closed-cooling-kits.aspx?pagenum=3

I've seen two different full closed systems depending on if you have V-Drive transmissions or not. On v-drives the heat exchanger needs to fit between the exhaust elbows and tubes. The v-drive heat exchanger has a larger diameter.

I've asked MerCruiser for a full system and they stated that they don't have a full system because the exhaust manifolds generate too much heat. No sure if i buy that a full closed cooling system couldn't be design to handle it, but that's what MerCruiser said.

Let us know how you make out.

 

[joeyleggz]

considering I already have a half system with the heat exchanger and a freshwater call block I'm looking for anyone with input on whether or not you can just re-plum some hoses with the existing set up and now have the manifolds fresh water cooled as well as the block


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[Sublimetime]

NO- you cannot just replumb to include the manifolds, they add to much heat and the heat exchanger cant keep it all cool at higher rpm's. You need larger heat exchangers, and you should use new manifolds if you switch to full system because your current manifolds are contaminated.

 

[joeyleggz]

The research that I did today let me to believe that the heat exchangers for 7.4 are of the same capacity weather is half or full cooling the only difference I can see is the nipple configuration for the hoses and yes I am putting new manifolds on this is why am investigating going to full cooling


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[Sublimetime]

I did the change over years ago, and as matter of fact I still have the old heat exchangers,(FOR SALE_like new). The replacements were longer and bigger diameter.

 

[Saverio]

It doesn't make sense to me either. all my other searay were full fwc. why did it come from the factory with just the block. the exchanger does look like the same size from old boat

 

[Brite Idea]

They sell half systems and full systems so yes you can cool the manifolds if your heat exchanger and water pump can move enough water to cool the manifolds.

 

[Bt Doctur]

A full system needs a thru hull fitting, you cannot pull that much water thru a outdrive.
You do need a HX designed for a full system ,

 

[joeyleggz]

I already have a half system I have inboard 7.4 with heat exchanger I'm just trying to find out if anybody had re-plumbed to go to the full set up


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[Sublimetime]

The amount of BTU's(heat) that the motor and exhaust manifolds when plumbed together will create is to much for the stock 1/2 half system heat exchanger.

I had the half system on my last boat, I myself, changed it to a full system and I am positive that the heat exchanger is LARGER. Even he cradle bracket that holds the heat exchanger is a different size.

 

[joeyleggz]

After speaking with mercury they will not comment and do not want any part of cooling a big block and manifolds that doesn't make any sense to me because crusader which is also a GM block and other manufactures all have big block full cooled systems meaning block and manifolds as others have stated it is clear that there is a aftermarket following for full cooling big blocks scratching my head with Mercury


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[kap2]

As stated in my earlier post, I got the same feedback from Mercury - they don't offer a full FWC system. You should call CP Performance who does offer the system and get their take.

From all my research you can not use the half FWC heat exchangers because they don't have enough capacity. The full FWC kit comes with a larger heat exchangers. There is a specific kit if you have v-drives that are similar in length to the half system exchanger but much larger in diameter.

Good luck.

 

[joeyleggz]

Thanks for the replies gentlemen it's just really chaps my a** The way mercury designed this .running such cold water through a hot manifold lens to condensation formation which many people have claimed is the reason why it's such a flawed design that eventually moisture works its way into the combustion chamber my friend has a 33 tiara with crusader 454s for freshwater cooling and has never had an issue of any kind in all the years he's owned the boat


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[Sublimetime]

I had countless issues with unbelievable corrosion caused by the condensation that was caused by the extreme temp. differences when the motor is run at low rpm's. That combined with the large valve overlap ground into the camshaft caused water to be GULPED back into the elbows. I placed a small section of CLEAR hose coming off the elbow connecting to the muffler, at idle 700 rpm up to around 1350 rpm the water would be so aerated and mixed up at the outlet of the riser you could see it get sucked back in.

mercuries quick fix in following years was the installation of "turbulator plates" under the elbow gaskets

 

[Sublimetime]

Check the thread below this one about the ejected spark plug--you guys are both fighting the same bad design motors with endless related issues.

 

[joeyleggz]

Check the thread below this one about the ejected spark plug--you guys are both fighting the same bad design motors with endless related issues.

Unbelievable reading that post I am actually repowering the starboard motor because it Grenaded in the fall now I'm looking at a brand-new long block and all new coolers and swapping over all the other items I thought mercury used to get involved or warrantee some of these water reversion issues


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[joeyleggz]

Also for the cam overlap didn't they suggest to use resonators?


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[Sublimetime]

yes in-line resonators get clamped inside exhaust hose except the placement has to be exact, and if you don't have the required straight run of hose on each side you can' use them.( 17" I think it is)

Get the turbulator plates.