8.1 Horizon Exhaust Manifold Replacement

[Dasch Boat]

I am about to pull the trigger on purchasing new stainless steel (Hi-Tek) exhaust manifolds to replace my stock aluminum units before they disintegrate. I have a few questions that I'm sure CSR members will be able to answer:
- The SS manifolds require 1" long bolts, I want to use 318 SS bolts, is this acceptable ?
- Can anyone confirm the bolt size ? I believe they are 8mm but I don't know the threads per inch or metric equivalent. (I would like to to pre-order)
- I intend to use flat and lock washers, is this okay ?
- Do the manifold bolts pass thru the water jacket requiring sealant ? Or is anti-seize enough ?
- What are the torque requirements ?
Any other tips would be greatly appreciated.
Thanks
Tom

 

[my3sons]

Tom,
I replaced mine this spring. I bought merc cast iron manifolds, which are direct replacement for the aluminum. so all the hardware was the same and I bought a few extra bolts and washers, but ended up sending them as well as tubulator gaskets back. All the old hardware was like new so I just reused it, the turbulators come with gaskets affixed to them, so there is no need for just the gaskets, see the link below where I discuss that.
The bolts are 8m, there are two different lengths, if I remember right, they are 35mm and 70mm, shouldered, but the aftermarket manifold you are using obviously use a different length.
There were no lock washers used, just flats.
Merc recommended loctite on the threads, however I used an anti seize compound, although the bolts that I removed had no evidence of anything being used at the factory. The bolts do not pass through a water jacket, and my manifolds were the w/o water rail type.
Torque was 25 ft pounds, working out from the centers in a few increments.
Check out the comments on the water temperature sensors, I broke 3 out of 4 trying to remove them, they are PLASTIC.
It was a fairly straight forward job, I took the time to do a little touch up painting, and some other things while I was doing it to take advantage of the accessibility that having the manifolds off provided.
Good luck

http://clubsearay.com/forum/showthread.php?t=25441&highlight=manifold&page=2

 

[Dasch Boat]

Thanks for the feedback, I hope my salt water units come apart as easily as yours seemed to. I think I will pre order 4 temperature sensors also.

 

[BahamasBlair]

Hi,
I just replaced my manifolds with cast iron on both engines. (ouch!) Also had to rework the heads on the port side due to water ingestion.
One thing i have done is modified the seawater intakes to allow me to flush with fresh water with a garden hose after each trip. I have also started using "Salt-Away" as part of my flushing routine. If you are interested in seeing some photos I can send them in. Just let me know if you are interested.

 

[Dasch Boat]

Hi,
I just replaced my manifolds with cast iron on both engines. (ouch!) Also had to rework the heads on the port side due to water ingestion.
One thing i have done is modified the seawater intakes to allow me to flush with fresh water with a garden hose after each trip. I have also started using "Salt-Away" as part of my flushing routine. If you are interested in seeing some photos I can send them in. Just let me know if you are interested.

Salt Away is a great product, I am also setting up a fresh water flush system, setting the hose inlet after the raw water pump so that the engines don't have to be running. Should have all the fittings as well as SS exhaust system to me in about three weeks. How difficult was the removal on yours.

 

[BahamasBlair]

Hi,
You might want to reconsider where you will position the intakes. I'm far from an ace mechanic but I think it is best to flush with the engines hot and running. Something to do with the thermostat being open and allowing the flushing water to get all the way through the heat exchanger and the KoolFuel system which by the way, is also aluminum and tends to rot away with time. There are a lot of other threads about this issue. You may be able to find them with the search feature.
Good luck either way. I will post my photos on the weekend.
Happy boating.

 

[fwebster]

Whoa...........Stop right there guys!

You cannot flush an engine by injecting water after the water pump without the engine running. You will fill the cylinders with water that way. The engine MUST be running before you turn on the flush water. The best practice is to hook up the hose with the valve closed, crank the engine and let it stabilize on sea water, open the freshwater hose valve and then close the seacock.

 

[Dasch Boat]

Thanks Frank, I will rethink this one.

You cannot flush an engine by injecting water after the water pump without the engine running. You will fill the cylinders with water that way. The engine MUST be running before you turn on the flush water. The best practice is to hook up the hose with the valve closed, crank the engine and let it stabilize on sea water, open the freshwater hose valve and then close the seacock.[/quote]

 

[Chris R]

My SR dealer installed a flushing system on my boat. If memory serves, it's an actual Sea Ray part (?). I can take some pics this weekend and show you how it was installed. It works flawlessly.

 

[Chris R]

Thanks Frank, I will rethink this one.

You cannot flush an engine by injecting water after the water pump without the engine running. You will fill the cylinders with water that way. The engine MUST be running before you turn on the flush water. The best practice is to hook up the hose with the valve closed, crank the engine and let it stabilize on sea water, open the freshwater hose valve and then close the seacock.

[/QUOTE]

Also see my previous post as a reference.

The instructions for this flush kit I mention say something along the lines of: 1) close sea cocks; 2) start water flow (what I do is attach one of those little on/off valves on the end of my hose allowing me to turn the water on and off where it attaches to the flush inlet); 3) start engines; 4) run for 15 minutes (I run about 8 or 10); 5) turn engines off and then stop water flow.

I says very clearly to NOT run the water longer than 15 seconds before starting the engines. With the on/off valve at the hose end, I can turn on the water and walk two steps to the starter button in about 5 seconds.

 

[Hampton]

Hi,
You might want to reconsider where you will position the intakes. I'm far from an ace mechanic but I think it is best to flush with the engines hot and running. Something to do with the thermostat being open and allowing the flushing water to get all the way through the heat exchanger and the KoolFuel system which by the way, is also aluminum and tends to rot away with time. There are a lot of other threads about this issue. You may be able to find them with the search feature.
Good luck either way. I will post my photos on the weekend.
Happy boating.

I don't think it needs to be warm to fresh water flush, though it may help dissolve the salt. The thermostat controls the fresh water flow inside the closed cooling system, right? That system cools the block, but not many, if any, external components. They are raw-water cooled. Doesn't make sense, does it? Tranny cooler, KoolFuel, the engine heat exchanger and one other item gets raw water (oil cooler?). If you do not have a close cooling system, then what he said above would be correct.

 

[Dasch Boat]

My SR dealer installed a flushing system on my boat. If memory serves, it's an actual Sea Ray part (?). I can take some pics this weekend and show you how it was installed. It works flawlessly.

Please send photos.