4.3L Carb Mercrusier Auxiliary Heater

[Scott06]

The first pic is the return so that is correct

The second pic NO do not connect there, that is for exhaust

@Scott06 is correct, the plug on top right is to the intake port number 1, so don't use that

When you first posted a pic of your motor with serial number I took it as a 2006 carb motor and didn't notice the 6 port Thermostat housing so was looking at manual 25. The 6 port hasn't been used much since 1999 (manual 18). Could be yours was a new old stock or for some reason they used it on yours instead of the 6 port

So with that, look on the port side below the top hose and see if the temp sensor is there. If it is do not remove, then look on starboard side on housing on the intake for a plug (is it there)??

If temp sensor is installed, and the plug is on on other side, I will suggest what Formula did with my boat for the water heater. Remove the block drain plug (used to winterize). Attach a fitting and then a Barbed hose fitting and that will be the supply side for the heater.

To winterize just pull the hose off or attach another Tee fitting so it can be drained

I think if you look at pictures of the intake the water fitting in cross over is on stardboard side to left of thermostat housing, under the hoses.

there are two manifolds in this ebay add- I think what you have is the upper one pictured. Plug in water crossover is just below the thermostat port in this pic

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[68 - 390]

I think if you look at pictures of the intake the water fitting in cross over is on stardboard side to left of thermostat housing, under the hoses.

there are two manifolds in this ebay add- I think what you have is the upper one pictured. Plug in water crossover is just below the thermostat port in this pic

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So I see a temp sensor and an extra plug. Next to the sensor. So is that the one I use for supply and then the plug in the side of the water pump for return?

 

[alldodge]

Don't think that will work, that's more for raw cool water coming in from the pump. Biggest issue I'm having is finding a cut away view of you thermostat housing which is HERE and it's the pic on top.

The sensor on top is and is actually in behind a section in the housing so it sits in the water inside the block. The lower one is where raw water comes in. The pic below is similar but not the same (older style). The sensor is on top and lower section has cooler water

 

[68 - 390]

Don't think that will work, that's more for raw cool water coming in from the pump. Biggest issue I'm having is finding a cut away view of you thermostat housing which is HERE and it's the pic on top.

The sensor on top is and is actually in behind a section in the housing so it sits in the water inside the block. The lower one is where raw water comes in. The pic below is similar but not the same (older style). The sensor is on top and lower section has cooler water

View attachment 400339

So what would you recommend for a supply line? I thought maybe adding a tee fitting to that sensor but don’t think that’ll be a good idea as you said the sensor is inside.

 

[alldodge]

I would do what Formula did on my boat. Remove block drain plug from which ever side is closest to where you want to run the line. Connect fittings (barbed) so it will connect to hose feeding your heater. That is the supply line

 

[68 - 390]

I would do what Formula did on my boat. Remove block drain plug from which ever side is closest to where you want to run the line. Connect fittings (barbed) so it will connect to hose feeding your heater. That is the supply line

Thanks so much. I appreciate it. I’ll keep you posted once I get it installed. Happy boating.

 

[68 - 390]

I would do what Formula did on my boat. Remove block drain plug from which ever side is closest to where you want to run the line. Connect fittings (barbed) so it will connect to hose feeding your heater. That is the supply line

Do you recall the fitting size that went into the block? Did you install a tee fitting so you can still use the removable plug for winterizing? Just getting all my parts in order. Thanks again

 

[alldodge]

The block should be 1/4 NPT and Formula didn't use a Tee, they cut the hose about 1 ft from block and used a double 5/8 barbed fitting. To winterize just removed on side

 

[68 - 390]

The block should be 1/4 NPT and Formula didn't use a Tee, they cut the hose about 1 ft from block and used a double 5/8 barbed fitting. To winterize just removed on side

Great Thanks!

 

[alldodge]

Think I gave you the wrong size fitting, think it should be 3/8 NPT and not 1/4

 

[Bondo]

Think I gave you the wrong size fitting, think it should be 3/8 NPT and not 1/4

Ayuh,..... Chevy block drains are 1/4" pipe,.....