Cleaning risers

[Darol Wester]

Having run our boat (Mercruiser 350) in the salt 95% of the time we started removing and cleaning the risers every year. We've been scrapping and soaking them in muriatic acid then rinsing. It's a pain but it does the trick. For those that frequent the salt, how are you dealing with this problem, if it is one? Any tricks we should know about?

Also, no matter what gaskets we use at the riser/manifold, there's always leakage to some degree. We've tried the factory gaskets and have made some of our own and used a sealant, but can't seem to get a good seal. Is it possible? We have followed all the torque specs.

 

[Don S]

Re: Cleaning risers

Forget it.
When you clean them, you eliminate your first line of defense (an overheat because they are plugged) No you go straight to salt water in the cylinders when the die .................. that means they take the engine with them.
The gasket surface has to be clean, flat, smooth, and all metal. Not that black carbon stuff that causes leaks.

 

[Darol Wester]

Re: Cleaning risers

I will clarify that the leaks I'm speaking of are on the outside of both risers though I did see a little evidence of rust on the inside in one spot. Can you have the surfaces of the manifolds and risers milled if need be, with out any problems, assuming it doesn't need too much?

 

[Don S]

Re: Cleaning risers

According to the manual, .010 max removal

 

[Darol Wester]

Re: Cleaning risers

I do appreciate your help Don, but, I need you to clarify what you mean by

"Forget it. When you clean them, you eliminate your first line of defense. (An overheat because they are plugged.")

We were having heat problems until I came here and you guys pointed out that the risers might be plugged, which they were. We actually bought new risers and were planning on rotating them and cleaning the spare while it was off to be ready for next year.

 

[Don S]

Re: Cleaning risers

If a riser is plugged, throw it away it's junk.

 

[bjcsc]

Re: Cleaning risers

I'm no Don S, but I'll tell you what the problem is in simple terms: When there is enough corrosion to plug the riser, your engine will begin to run hot - that's you're first line of defense - your first warning that you have a problem. Remember 2 things: 1) that wall is not very thick to begin with and 2) you can only see/affect a very small part of it. If you clean them as you intend, there will be no wall to scale off and plug the riser. Instead, the failure will be catastrophic and the already compromised wall will fail and send water directly to your cylinders via the exhaust manifold. This will happen while underway. Water does not compress. You can guess what happens next.

Risers/manifolds are consumables in salt water. The only "trick" is to be proactive and check them. I check mine at the beginning of every season. One hour and two gaskets is worth the peace of mind. Heavy salt water use and/or no flushing could require replacement every three years. When they get iffy or scaly plugged - replace them. It's just not worth it...

 

[Darol Wester]

Re: Cleaning risers

That's exactly what I was looking for BJ. Thorough explanations makes a world of difference for those of us that are NOT on top of this game. That's why we come here. If you were looking for information about floorcovering, I'd hope you'd be looking us up @ the floorpro. The internet is the greatest!

Thanks again. Great info.