Non-Vortec 5.7 Mercruiser Themostat Housing Question

Quarterwave

Petty Officer 2nd Class
Joined
Sep 16, 2013
Messages
118
Hi everyone,

I'm converting a non-Vortec head 5.7 truck engine into a marine engine for my bowrider and I'm having an issue finding a correct thermostat housing.

The 5.0 Mercruiser that I recently took out had a 6-connection thermostat housing. Attached is a pic of it when it was in the actual boat....

I've also tried adding a link to a web page that has a full diagram of it. Hopefully it works.

The issue is that this type of thermostat housing is no longer available and I'm wondering what other type I can use or what alternatives will work for my application.

I am running exhaust manifolds with a 4 inch riser that are not a closed system (they pull sea water in from the outside).

Any help is appreciated!
 

Attachments

  • photo276879.jpg
    photo276879.jpg
    92.8 KB · Views: 2

Fun Times

Moderator
Staff member
Joined
May 16, 2009
Messages
9,249
First just to let you know while I know it's a reference point, your second post isn't permitted here on iboats because of who they are to iboats.....But more importantly before ordering, Hopefully you still have the option to see if your original T/housing has the check ball valves or not as there would be two designs of this style housing but only one to fit your engine combination.

The one you posted mentions the big block 7.4L which may or may not be used on your 5.7 engine combination because of (us not knowing) your cooling system design.... If you look further into the listings on that website by clicking on "More Info", it will take you to another page to where if you click on the page down below where it says page "850", you'll see the options of kits to choose from. That page 850 is from Mercruiser and is used as a guide. Thermostat Housing w/o checkballs, NLA
Order kit 87290A23 for V-6 or V-8 (305/350 cid).
Order Kit 90736A24 for V-8 (454/502 cid)
Additional information about this part can be found on page(s) 850 of the Quicksilver Marine catalog.
16413A 9 - HOUSING ASSEMBLY O NLA


Depending on engine and drive combination you have typically depends on if need the check balls or not to avoid overheating issues. Some of the newer designed housings have different size holes in the housing which take the place of the check valves for certain engine model combinations.

Do you have an engine mounted sea water pump like a Bravo drive uses or is the water pump drawn up from an original Alpha 1 (Gen 1) style stern drive water pump impeller inside the stern drive? V6 AND V8 THERMOSTAT HOUSINGS

Either way once you find the correct part number you should be able to get a kit to fit or search the original parts number online or ebay and find something either new old stock laying around or maybe a good used one if desired.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
43,398
Not knowing which model, I'm going to assume you have one similar to the one on the left

Cooling Old Style.png


Thinking you want to go to new style like this, which is a V6 but is the same for you. As FT mentioned, if you have a bravo drive then the inlet hose comes from the belt driven pump. You will also not have item C

V6 Open cooling.jpg

You will need this thermostat housing

T-stat Housing.jpg

The above exhaust manifolds and risers can also be changed to dry type
 

shaw520

Chief Petty Officer
Joined
Aug 27, 2009
Messages
634
Can someone explain what exactly the check balls do?,... Ive removed mine from a 88' Merc 5.7 and I dont see a difference in running temps.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
43,398
Can someone explain what exactly the check balls do?,... Ive removed mine from a 88' Merc 5.7 and I dont see a difference in running temps.

They provide a slight restriction to keep the block full of water, with out them the block can have some air pockets develop, so you can get a hot spot. Its also used to slow the water going thru the manifold so they stay a tad warmer then the elbows
 

Quarterwave

Petty Officer 2nd Class
Joined
Sep 16, 2013
Messages
118
No Title

Hi everyone,

I just wanted to follow up on this thread to show the new thermostat housing installed on the new intake...

I also added the water pump but took this photo just before doing so...

Lots more to do (including needing to get all the cooling system hoses etc...), but for those that are researching this topic in the future, this is where things are at the time of posting!
 

Attachments

  • photo279336.jpg
    photo279336.jpg
    183.6 KB · Views: 3

Red955i

Cadet
Joined
Apr 13, 2012
Messages
26
I was under the impression there were far greater differences than what is mentioned here. The Thermostat housings that have the check balls, and the reworked one that replaced them have 6 bibs. The one in the bottom picture has only 4. The difference is, as I understand it, the 6 bib thermostat housings are for warm water exhaust, the 4 bib are cold water exhaust. You will note in the 4 bib housing you have the inlet from house from the seawater pump and the large hose feeding the circulatory pump. The other two hoses go to the bottom of each exhaust manifold where the water then travels upward through the riser and out the elbows. The gasket used between riser and manifold is the full open design. In the 6 bib (ball or no balls) design there are two additional hoses that go directly to the risers bypassing the manifolds. This is the warm water design. The reason Mercruiser changed was both the Alpha pump and the Bravo seawater pump draw more water than is needed by the engine. When this cold water mixes with the heated water in the thermostat housing it drops the water temperature enough that it may allow condensation to form in the exhaust if the water temperature delivered to the manifold was lower than (I think the number was 110 degrees) Therefore the warm water design was set up. It bleeds off the excess cold water from the impellers and directs it directly out the riser thereby increasing the temperature of the water entering the manifolds and eliminating the condensation threat.
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
13,454
Interesting.....I recall reading about the cool water vs warm water designs....based on this info it appears that all OMC/Volvo systems (except the newest Volvos) are cool water designs because the exhsust manifolds run 85-100* unless you are running on plane and even then they rarely top 135 if everything in the cooling system is in good shape.
 
Top