Whats your thoughts on CMI headers?
04-13-2019, 06:47 AM
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Whats your thoughts on CMI headers?
I'm just thinking of things right now. It's a rainy day..lol..I still have a few years before replacing my Mercruiser manifolds. I was looking at the CMI. I know they are A LOT of money and I need 2 sets, BUT I'm thinking of reasons to spend the extra cash and this is what I came up with..IF in 4 years I love the boat so much that I plan on keeping it for a long time. So far I'm 3 years in and I don't want anything more or less. I could offset the price a little with my stainless Elbows also. What's your thoughts? Remember I'm in salt water also.
#1=They are Stainless and would never have to be changed as long as I own the boat.
#2= In the back of my mind I won't have to worry so much about blowing up a motor for water intrusion. ( less joints to fail )
#3= I won't have to flush my motors every time I come in ( That's just the way I am)
#4= Say a little more power ( I'd tweek my props again if I had to )
#5= Resale value
#6= COOL FACTOR.
#1=They are Stainless and would never have to be changed as long as I own the boat.
#2= In the back of my mind I won't have to worry so much about blowing up a motor for water intrusion. ( less joints to fail )
#3= I won't have to flush my motors every time I come in ( That's just the way I am)
#4= Say a little more power ( I'd tweek my props again if I had to )
#5= Resale value
#6= COOL FACTOR.
Last edited by mnm99; 04-13-2019 at 07:19 AM.
04-13-2019, 07:20 AM
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Is that a list of reasons why to buy CMI!? If so, many of them are wildly inaccurate.
1. CMI’s fail all the time. Actually they have been known to fail the most. Welds give up due to corrosion/vibration/heat cycling.
2. CMI’s have marginal performance improvements if any especially with smaller power.
3. They don’t last forever. See item 1 above. Ours failed after 8-9 years causing top ends to be re-done. Some folks experienced failures after 2-3 years.
4. Cool factor sure. But anyone who knows the truth might shy away. Lots of people are going with other manufacturers I.e. stainless marine, etc.
1. CMI’s fail all the time. Actually they have been known to fail the most. Welds give up due to corrosion/vibration/heat cycling.
2. CMI’s have marginal performance improvements if any especially with smaller power.
3. They don’t last forever. See item 1 above. Ours failed after 8-9 years causing top ends to be re-done. Some folks experienced failures after 2-3 years.
4. Cool factor sure. But anyone who knows the truth might shy away. Lots of people are going with other manufacturers I.e. stainless marine, etc.
04-13-2019, 07:37 AM
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The reasons seem strange but as for the failures those had a lot to do with the cheap Merc version.
But if you have mild power and want cool factor, ease of maintenance get the E—tops. 19 years on mine and they are fine.
You still have to flush no matter what you have. Here’s one, people say they don’t like to run coated aluminum heads in salt but will put exhaust on and not worry?
Big thing, flush and flush with a LOT of water volume, no cheap 1/2” hose junk.
04-13-2019, 08:02 AM
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I have etops on both of mine and love them, but i have to admit, im hearing great things from people with real big hp that are running the stainless marine risers and the KE lightnings. they dont have the bling of a header, but if it gives the same or better hp rating and better longevity I might be tempted to use them on my next project.
04-13-2019, 08:35 AM
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I have etops on both of mine and love them, but i have to admit, im hearing great things from people with real big hp that are running the stainless marine risers and the KE lightnings. they dont have the bling of a header, but if it gives the same or better hp rating and better longevity I might be tempted to use them on my next project.
But if he just has a 496HO I doubt he would notice and for that matter I have dyno sheets that show the KE lose some mid range on a small motor.
If if I had a staggard boat and needed to buy I would buy the KE’s and paint to match.
04-13-2019, 08:45 AM
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I wouldn’t spend 10-12k on headers in that boat, if that second picture is your boat. Looks like a cruiser, v drives. Tail pipes would be a project alone. HP wise the stock merc manifolds have shown to flow pretty good.
04-13-2019, 09:28 AM
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Thanks guys. I have no Idea about the reliability and thank you for the input.. It wouldn't be going thru hull either. Just a replacement for stock. Yes it's a 340 cruiser with V-Drives. I'm sure I won't go the header route with this boat the more I research, I was just seeing if anyone ever used the CMI. Within a couple years I'm hoping to be in a gofast like you guys.
04-13-2019, 09:41 AM
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I don’t have 1 bad word to say about my etops. I can see every spark plug on both sides, I can hold them up with one hand to mount,there are no riser gaskets,they look great, and the midrange grunt difference was unmistakable. I only gained about 100 rpm on top though. 5 years so far and flush every time
04-13-2019, 10:19 AM
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Thanks guys. I have no Idea about the reliability and thank you for the input.. It wouldn't be going thru hull either. Just a replacement for stock. Yes it's a 340 cruiser with V-Drives. I'm sure I won't go the header route with this boat the more I research, I was just seeing if anyone ever used the CMI. Within a couple years I'm hoping to be in a gofast like you guys.
04-13-2019, 11:18 AM
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18 years on my CMI ETops never one failure. The bad wrap comes from the Merc spec headers. Inferior stainless alloy, no cool collar at the flange, and no heat treating make them failure prone. Standard CMI headers are pretty bulletproof. That said, you still need to flush them if running in salt.
Honestly with your boat, I’m not sure it’d be worth the cost. You may not see any gain....it’ll sound a little cooler if the exhaust is above the water
Honestly with your boat, I’m not sure it’d be worth the cost. You may not see any gain....it’ll sound a little cooler if the exhaust is above the water
