Engine Sensor Questions - 1996 5.7L Vortec

[76SeaRay]

Engine is a scratch built but pretty much a stock 1996 Chev 5.7L Vortec with the Xtreme Marine roller cam and roller tip rockers (yes, it is marinized). I currently have a marine Rochester QJet carb.

So, getting ready to light this engine off on a run stand and need to get the appropriate sensors installed. The list so far is as follows:

Oil Pressure Sender - Mercruiser P/N 815425T
Water Temp Sender - Mercruiser P/N 806490T
Thermostat - ???????????

The T-Stats that I have found say closed cooling but I will be going with raw water cooling. Temps seem to be either 140 or 160. Since this is a vortec, I believe it should be run a little hotter so thinking of going with the 160.

Does anyone know the part number for the correct T-Stat for raw water cooling and have any thoughts on the 140 versus 160 issue??? Thanks....

 

[alldodge]

My guess would be 806235A1

New oil pressure sender is 8M0068784, but old part number will also work

 

[76SeaRay]

Thanks but the number you gave for the thermostat comes up as the housing. Looking for the thermostat part number..

 

[alldodge]

Not sure you want to use a closed cool thermostat housing with open cooling. What is the housing part number?

 

[76SeaRay]

I don't have the housing numbers in front of me as I am at work but I have three of them in varying conditions. This will be raw water cooled even if I have to get a new housing (which I think was the number you gave me) so trying to figure out the right thermostat. Again, this is a scratch build engine so not a rebuild of an existing one...

Thanks...

 

[alldodge]

Try to find a pic of it one the net, might be able to find the stat for it

 

[76SeaRay]

This is the closest I can come to an equivalent Mercruiser engine matching what I am building:

MERCRUISER : 5.7L GM 350 V-8 1988-1995 Model Serial Ranges 0B525982 THRU 0F600999

Except that this eingine is built on a 1996 5.7L Block (880) with Vortec heads. The thermostat listed for the above is 8M0109441 (160 degree) but not sure if that is correct for vortec heads. This thermostat is listed as for fresh water cooling and not raw water.

 

[76SeaRay]

Also having a hard time sorting out which cooling system. It seems there were 3 designs in this time period. Design 3 appears to be what I need but not sure.. Design III also mentions Alpha and I think all 3 are raw water cooling. I have Osco Exhaust manifolds similar to those Mercruiser ones called out for the engine serial number range I listed in the other post.

 

[alldodge]

Guess I'm missing something but the motor shows 3 different Thermostats The housing I previously listed prior uses the stat you listed (design 3). All of the onces on your page link are the ones piced below and all at the time were open cooled

 

[76SeaRay]

Thanks, I will go with that thermostat.. It appears the description from one supplier to the next varies between open and closed cooling systems. Some say it is for closed and some say it is for open.. I will just check it periodically for corrosion..

 

[76SeaRay]

Ok, so still going around in circles on how the cooling system connects. I have the mid riser OSCO manifolds and I think that I need to use the Standard Cooling Design III. But, it is unclear to me how the hoses connect to all the fittings. Does anybody have a clear drawing of how everything connects to the manifolds, oil cooler and water pump and to the Alpha One? The thermostat housing I have is much older (47440 and 87110) so I will need to buy one to fit whatever the correct layout is...

I ran across this video https://www.youtube.com/watch?v=gI7UolkuC4w that has a clear walk around of the hose routing, however, the thermostat housing doesn't look like the Mercruiser drawings for part number 860256A3.. I assume though that the OSCO exhaust manifolds would connect as shown in this video...

Thanks...

 

[alldodge]

How about this

 

[76SeaRay]

Yup, that's exactly what I needed... Now to find a thermostat housing that doesn't cost a fortune.... Thanks!!!

 

[76SeaRay]

Two additional questions:

Why do some engines have lines running to the thermostat housing from both the top of the exhaust (riser) and the bottom of the exhaust on each side?

Where is the best location for the temperature sensor. I would tend to mount it in the block (assuming room) but I see some diagrams showing it in the side of the thermostat housing.

Thanks..

 

[alldodge]

Talking open cool system only

The older style use what was called warm manifolds. Less water would flow thru the mans and the rest would flow to the elbows. This kept the mans a bit warmer then the elbows. Because to much of an issue most times so it was stopped

Best place for sensor is in the thermostat housing. Heat rises and placing it in the block would be difficult unless using the drain ports, but that would be to low

 

[76SeaRay]

Thanks, I will not worry about it then and build it per the diagram above in this thread. It does make it interesting to be building from scratch to get the right parts in all the right places without a serial number from Mercruiser for the engine to be a guide... It takes a lot of looking at pictures, watching video's, and asking a lot of questions.. I have the sensors now and the thermostat housing and gaskets are on the way...