4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

[theboatfloats!]

I'm upgrading my Mercruiser engine and intake manifold from a 1992 4.3 V6 to a 2011 4.3.

I am reusing my 1992 electrical harness, my 1992 carb, and all other accessories.

I got a new 8 bolt manifold to fit the 2011 4.3L

Research and dealers of remanufactured and new engines tell me that I can move the thermostat housing from the 1992 to the 2011 with no problems. They're correct, as the holes match perfectly.

But my old 1992 thermostat housing with 6 hoses and 2 sensors is old, rusty and cracked. So I need a new one.

2 questions:

1. I want to buy a new thermostat housing, but the 6 hoses ones are quite pricey.
I see that some 4.3 V6 thermostat housing have 4 hoses such as:
Housing | Thermostat | GM V6 & V8
some are even less expensive than the above link
There are some 4.3L Mercruiser and Indmar 4.3L V6 (similar to Mercruiser) that use 4 hose thermostat housing: they install unrestricted gaskets between the exhaust manifold and risers, put brass plugs in the risers where hoses 5 and 6 would go, and only have hoses 3 and 4 connected to the manifold. Has anyone tried that and what were the results? Any overheating? Any problems?

2. Either for the 6 or 4 hoses, I see that some have either 1 or 2 sensors. Why do they have 2 sensors to measure temperature? Do you really need that many? Can I use 1 sensor and if so, what do I do with the existing wire for 1992 electrical harness?

Just curious.

Thank you.

 

[achris]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

Question #2. 2 sensors. One sensor is the gauge sender, and the other is the overheat warning system temperature switch.

Question #1. difference between 4 hose and 6 hose. The 6 hose system keeps only warm water in the manifolds, whereas the 4 hose system has alternating warm and cold water through the manifolds.

I saw the link you have in you original post. That is a cheap and nasty knock-off, and could lead to some overheat issues. For the 4 hose system to work properly, use the OEM Merc thermostat housing. Part#-860256A3. Yes, it's more expensive, but it works properly... And nobody said boating was cheap.

Chris......

 

[britisher]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

I did a 4.3 v6 engine swap dfrom an original 89 to a 93 4.3LX. I found that on the thermostat housing there is a version for the Alpha drive and one for the Bravo drive. They look similar but aren't. One allows more water to pass through. But they look totally diffrent to those in your pics.

 

[theboatfloats!]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

thank you guys.
I learned something about The Difference Between Warm Vs Cold Marine Exhaust Manifolds:
The Difference Between Warm Vs Cold Marine Exhaust Manifolds | Performance Product Technologies

Does anybody know the Sierra part numbers for each of the sensors on the thermostat housing ?

 

[achris]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

thank you guys.
I learned something about The Difference Between Warm Vs Cold Marine Exhaust Manifolds:
The Difference Between Warm Vs Cold Marine Exhaust Manifolds | Performance Product Technologies

Does anybody know the Sierra part numbers for each of the sensors on the thermostat housing ?

I don't generally use non-OEM, so here's the OEM numbers. That will help you find the aftermarket parts (if there are any).

Water temperature sender: -806490T ($26)
Water temperature switch: -48952 ($71)

Sender is for the gauge, switch is for the alarm.

Chris......

 

[britisher]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

I have a question on this situation. Having read the Perfprotech article, the thermostat housing I was talking about was the 4 hole Cold water housing shown at the top in the article. I also know from Perprotech that the housing comes in Alpha design (860256A 3) and Bravo design (860256A 4) depending on the stern drive designation. There is a technical reason for having 2 different designs. That said TheBoatFloats wants to install a thermostat housing designed for a 1992 4.3 V6 on a 20114.3 V6. Whilst Chris's answers seem to indicate 'he can', my question is 'should he?', if the thermostat housing designed for his 2011 4.3 V6 is not that? There are reasons for everything and I don't see any answers as to that question.
On a final note, the 4 hole thermostat housing shown in the PerfProtech article (860256A 3) is available in a Stainless Steel version from a supplier (offshoreonly.com) that states it replaces both the Alpha & Bravo 4 hole housings?
Confused?????

 

[theboatfloats!]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

thank you achris for the part numbers.

britisher: yes I am curious. Since it seems that for the exact same 4.3L I can buy either a new 4 hose or 6 hose thermostat housing, which is the difference Between Warm Vs Cold Marine Exhaust Manifolds as per:
The Difference Between Warm Vs Cold Marine Exhaust Manifolds | Performance Product Technologies

I am wondering if there a pro and cons to each setup, are they both "good" and just different ways to achieve the exact same goal.

 

[achris]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

I am wondering if there a pro and cons to each setup, are they both "good" and just different ways to achieve the exact same goal.

:thumb:

 

[theboatfloats!]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

OK achris, so they're 6 of 1 or 1/2 of dozen of another!

Thanks for your help you've given me.


achris:

Do you have a Mercruiser part # for a timing cover WITHOUT sensor for a 2007 thru present 4.3L V6 ?

Are the timing covers the same as pre-2007 or are they different ?

Thanks for the help!

 

[achris]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

achris:

Do you have a Mercruiser part # for a timing cover WITHOUT sensor for a 2007 thru present 4.3L V6 ?

Are the timing covers the same as pre-2007 or are they different ?

Thanks for the help!

I believe GM changed to an aluminium cover in 2007. The pre-2007 was composite (and a load of rubbish). And not-interchangeable.

Composite cover part# -809893T (without sensor)
Ali cover part # -879194362 (I don't believe they are available without the sensor hole. Just a plug goes in when the sensor is not required.)

Chris.....
If you need an ali cover, I have one going cheep...

 

[britisher]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

Sorry for coming back on this and I don't want to appear pedantic, but 6 of 1 and half dozen of the other is not a real answer. Why would Mercruiser go to all the time and expense of designing 4 different thermostat housings if 1 would suffice? They obviously put a specific designed part on a specific range of engine for a technical reason. So far I haven't seen one.
I did an engine swap on mine last year from original 89 to a 93 or 94 4.3 V6 as the original engine died. The original Alpha sterndrive was refurbished. I later found out that my 4 hole TStat cover is a Bravo cover as that engine was originally powering a Bravo drive. Outwardly, the ONLY way to tell the difference is one has the drive name cast into it. PerProtech state that you should have the correct housing for the correct drive and must not use the wrong one. But no-one can give me a clear answer why?
No-one wants expensive engine repairs because a part was used 'because you can' rather than 'because you should/shouldn't'
Can anyone provide a clear answer? Thanks

 

[theboatfloats!]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

Thanks achris,
I already have an aluminum cover with sensor holes, so I just would need the plugs then. Do you have those plug part numbers?
Thanks!

 

[theboatfloats!]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

I agree with you britisher: I also would like to understand this issue between all these little variation in thermostat housing design for the same exact engine, without risking an overheated engine for selecting the wrong one.

 

[achris]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?

...Can anyone provide a clear answer? Thanks

Probably not. Mercury are not in the habit of explaining why they change things around...

Thanks achris,
I already have an aluminum cover with sensor holes, so I just would need the plugs then. Do you have those plug part numbers?
Thanks!

As for the plug... I have no idea. I can't find one on the parts diagrams anywhere. Sorry.....

Chris......

 

[theboatfloats!]

Re: 4.3 thermostat housing: 6 hoses or 4 hoses? 1 or 2 sensors?



Update on converting a 2011 Silverado 4.3 truck engine with 234 casting for marine use. Work is complete and engine is running smoothly:

1. could not find a Mercruiser timing cover that fitted, even the Model Number provided here by people who helped me, as the hole pattern were not the same. So I took my aluminum one that came with the truck engine to a machinist, who for $60, welded the bottom sensor hole shut, welded the sensor hole under the water pump shut, and grinded that same sensor hole flush with the cover, as it conflicted with the water pump.

2. Water pump from 93 did not fit, as one of the leg had 4 holes, but engine casting. I confirmed with Sierra that their water pumps are bi-directionals. So I installed a Sierra #18-3506 water pump.

2. Thermostat housing: I ordered and returned a GLM cast iron housing with 6 hoses for $300, but I was not impressed with the poor workmanship and it was made of cast iron. So I installed a Sierra #18-1989 which is made of Stainless Steel which cost me $200 + the cost of 2 sensors. I think that Stainless Steel will last longer than cast iron.

3. Harmonic balancer. That is a misnomer, as it is actually an Harmonic Dampener. I could have used the one from the 93 and it would have worked according to several Harmonic Dampener experts (sellers and harmonic rebuilders) that I spoke to. But I took the one that came from the 2011 Silverado with 234 casting and had the protruding lip grinded off by a machinist for $40. Then I installed my 93 v-beltpulley on top of it and bingo.

4. All accessories from the 1993 fit perfectly in front of the 2011 engine,as the bolt patterns were the same.

5. Brand new manifold that I bought for 93 fit perfectly.

6. I had to buy a new 8 bolt manifold as the 93 12-bolt manifold did not fit.

7. the 4 barrel Weber carb from 93 fit perfectly on new manifold. Changing to carb from truck fuel injection worked.

8. I reused the 2011 oil pan that came with the truck, same clearance under the pan as the 93

9. The 93 distributor fit perfectly on the 2011

10. The 93 starter fit perfectly on the 2011

Anything can be done if you put your mind to it. Do your research and verify.

And thank you to all for all your help. There is great help here!

Video of 2011 with casting 234 running engine:

<span style="font-size: 7.5pt; line-height: 115%; font-family: Verdana, sans-serif;">https://www.dropbox.com/sc/r30vhmz8yzthxma/YE7jxkH_d-