manifolds and elbows

J

JAYROCK

Member
Joined
Sep 18, 2007
RO Number
28607
Messages
272
Two part question....
1. What are the warning signs that your manifolds and elbows are going bad?
2. I see that there are aluminum as well as cast iron. what is the pros and cons of both?

BTW i boat in fresh water 99% of the time.Maybe a week every two years we will head down to the gulf coast. Thanks
 
how old are the manifolds and risers? freshwater is good and they will last longer but not forever. If they're over five years you need to do a visual inspection. If you do it yourself it's about a two hour job per engine but if your paying a yard it probably pays to have new ones installed.
 
1.) Sometimes not much more than the fact that the casting date is greater than 5 years in salt water.
2.) I'm not familiar with aluminum and would personally steer a wide berth around anything unusual.

You really just want to replace these things on a schedule. Observation is in practice a poor way of handling them. they are relatively inexpensive compared to the cost of an engine and like a brake pad, your going to have to do it anyway, so saving a few more days wont make much a differnce but may be more risk than you want.
 
Most important, are you fresh water cooled or raw water cooled?

I have switched over to aluminum but have full FWC.
 
quote:
Originally posted by jtybt15

Most important, are you fresh water cooled or raw water cooled?

I have switched over to aluminum but have full FWC.

Click to expand...


I believe the operative words in your response are "FULL FWC". 1/2 FWC in salt water with Al is a recipe for disaster unless chemists have come up with something I am not aware of.

I have full FWC as well. I honestly did not know the difference until 2 weeks ago and have owned this boat since 2007. Fortunately I am in fresh/slightly brackish water and my engines have flush units built in.
 
quote:
Originally posted by KiDa

I have full FWC as well. I honestly did not know the difference until 2 weeks ago and have owned this boat since 2007. Fortunately I am in fresh/slightly brackish water and my engines have flush units built in.

Click to expand...


[:O]
Dave, I'm surprised [:P]
 
Back to the original question

You have to separate the riser from the manifold and inspect them. Unless there is an unseen casting defect, the most susceptible part for corrosion is the manifold/riser joint. And the area that is most susceptible to failure is the mating surface between the exhaust gas and cooling water. The exhaust gases are most corrosive and salt water as the cooling medium makes it more so. You will notice the wall thickness is 1/8"-3/16" for the Merc manifolds. This is a poor design. In fact, the center rise design is a poor design in it's present configuration.
 
My boat spent its first 18 months in Tampa at a high and dry. The bilge hatch had a design flaw. The aluminum supports on the 3 pc doors would leak water ontop of the engines. Just a trickle, but enough to make things ugly! She had 150hrs on her in 08 when I bought her. Moved her here to NW La. fresh water. Now she has 475hrs on an 06 model.
Brite Idea may have said it best, if you are going to pay to separate them and LOOK, might as well pay to REPLACE.
 
Sure! I used to rod out and soak my manifolds and risers in muriatic acid to squeeze out every last ounce of use out of them. Then I went to just replacing them. Finally, I went to redesigning the whole exhaust system.
 
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