Looking for Magic Manifolds

Posted: September 1, 2012  |  Tag: Engines

By: Frank Lanier, a marine surveyor from Florida

I have a 2005 Maxum that I run in salt water, with two 5L EFI MerCruisers. It is time to replace the manifolds and risers, which is way overdue and going to be expensive. I installed a superflush system and flush both engines every time I use the boat. I have done my research and found a lot of different manifolds for sale at a wide range of prices. Are there any manifolds that are better than others? What would you recommend? I plan on having this boat for a long time and want to minimize the number of times I have to change the manifolds.
I can’t provide specifics on this particular engine; however, I can offer the following observations.

As manifold and exhaust-riser leaks can easily result in catastrophic engine failure, I always recommend in my surveys that they be routinely removed, inspected (for leaks, corrosion, clogging, etc.) and pressure tested as a regular maintenance item. This is particularly true for systems operating in salt water. How often depends on vessel location and use; however, pulling them every four years is a good rule of thumb, although you may want to do this more frequently depending on the age of the components.

I don’t know of any hard-and-fast rules regarding replacement time frames, and all boats are different, but after seven years of saltwater use, it’s probably time. Even if they test OK, in the back of your mind, you’ll likely still be worried about possible failure due to their age every time you run the boat. The extra peace of mind alone would likely justify the added expense of replacing them, particularly since you plan to keep the boat for the long haul.

I’m not really up on the various aftermarket manifolds and risers available for this particular engine. If you’ve gotten seven years on the current ones (which I’m assuming are OEM) with no problems, you probably can’t go wrong with like replacements.

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