Replacing Exhaust Risers only! Suggestions for installation on my 7.4L?

[Sea~Lah]

I've been informed that my risers are rotted (bought boat in October)
Just purchased new risers from ******* .com (117.00 each). They'll be delivered in a few days.
Plan on installing them later this week. Wondering if someone can walk me through removal of the old and installation of the new. Any tips would be greatly appreciated!!!!
thank you in advance!!

 

[NJMatt50]

My tip would be to change the manifolds too.. Who diagnosed the bad risers?

 

[Quint4]

Be sure and use the MERC graphite gaskets.

 

[Sea~Lah]

Where would I get Merc. gaskets from? Can I purchased them through West Marine?

 

[ardeprint]

Where would I get Merc. gaskets from? Can I purchased them through West Marine?

I use Marine Power Service
http://www.marinepowerservice.com

I second the consideration for manifolds by the way...

 

[Air O'Nautical]

Manifolds and risers normally get changed together in a raw water cooled engine.
If you have fresh water cooling, you may get away with just the riser elbows.
Because, the manifold is filled with antifreeze and there is a blocker gasket between the manifold and riser. The manifold may/should be OK.
Inspect it for and corrision with a flash light when you have the riser off.

The procedure is to first drain the block.
Remove the bolts.
Clean the mating surface perfectly.
Install the merc. graphite gaskets no extra sealant ($12 a piece from a mercury dealer parts desk).
Reinstall and toque mounting bolts to spec.
Easy enough but, use the correct gaskets.

 

[Sea~Lah]

My tip would be to change the manifolds too.. Who diagnosed the bad risers?

A marine mechanic

 

[Sea~Lah]

So I can replace the risers while the boat is in the water? right?
I was quoted $650 for the job. The boat is in Canada, so I'd have to add 15% tax to the bill. I'm looking forward to doing the job myself. Thank you all for your suggestions.

Manifolds and risers normally get changed together in a raw water cooled engine.
If you have fresh water cooling, you may get away with just the riser elbows.
Because, the manifold is filled with antifreeze and there is a blocker gasket between the manifold and riser. The manifold may/should be OK.
Inspect it for and corrision with a flash light when you have the riser off.

The procedure is to first drain the block.
Remove the bolts.
Clean the mating surface perfectly.
Install the merc. graphite gaskets no extra sealant ($12 a piece from a mercury dealer parts desk).
Reinstall and toque mounting bolts to spec.
Easy enough but, use the correct gaskets.

 

[CharlieN]

On the 268, the boat sits so low in the water that the joint between the Y pipe and the elbow is underwater. The water will enter pretty quickly once the rubber is loose. It is worth while to inspect the flappers which are also at this joint once you have them apart.

 

[Bt Doctur]

"the boat sits so low in the water that the joint between the Y pipe and the elbow is underwater"
Don`t think so,if that was the case the water would enter the engine. And if the install was that low in the boat you would have 4 or 6 inch riser spacers added.

 

[Sea~Lah]

Flappers have just recently been replaced. Thank you for your suggestion.

On the 268, the boat sits so low in the water that the joint between the Y pipe and the elbow is underwater. The water will enter pretty quickly once the rubber is loose. It is worth while to inspect the flappers which are also at this joint once you have them apart.

 

[CharlieN]

On my 268 and single engine, there is a 3 inch spacer between the manifold and riser and as I have I tried taking apart the exhaust system while in the water it will leak water in the boat. The joint for the Y pipe and elbow is lower than the exhaust manifold.

 

[Sea~Lah]

Update on Risers: Well I installed the risers this past weekend. It was very easy to complete. I would suggest it to anyone that is mechanically incline. It took about an hour for each side. The risers were purchased on line and cost $117 each including shipping. I purchased Merc. gaskets as suggested, $3.99 each at WM.

 

[boykster]

Excellent - I'm tackling this exact project as soon as my new parts arrive. I have a FWC 7.4L in my 250DA that I believe has the original risers still installed. It was primarily a fresh water lake boat for most of it's life, but I've had it in salt water in the puget sound since 2005 or so. I don't use it that often, and it is stored in a rack - I'm religious about flushing the raw water system on the muffs before it gets put away. I'm also going to be replacing the shutters - it has had that symptomatic 'clack clack' at idle since I've owned it and I'm finally getting around to fixing it.

I'll check out the manifolds when I have things apart, but since they are FWC cooled, I'm optimistic that they will be in good shape. Externally they look great - no signs of water leakage / rust / etc and I've never seen water in the oil.