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Mercruiser exhaust Modifications question

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Section - Hello To all, My boat has twin 7.4 mercruisers that both are out of the ...
   
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  1. #1
    Lt Commander
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    Default Mercruiser exhaust Modifications question

    Hello To all, My boat has twin 7.4 mercruisers that both are out of the boat for a rebuild. My question is the exhaust (behind the risers between the engine and mufflers) has a cast iron 90 elbow then a rubber 4 in hose into a tee. Hope you can follow what im speaking of here, they have been in salt water so I dont need to explain that one I want to replace the elbow and make a tee from stainless steel. Is that ok with the abyc to do that seems to me its better because its stainless. I hope you can picture what im talking about here. these elbows and tee have the rubber exhaust hose running to them then out the rear of the boat. They are not connected to the engine other than be the rubber 4in hose. Thanks Jamie

  2. #2
    Lt Commander
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    My computer is still broke Im in the parts room at work. Playin on there computer lol Jamie

  3. #3
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    Roger's Avatar
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    Most exhaust fittings are available in stainless steel as well as cast iron. My understanding is that stainless costs a lot more than cast iron and lasts only slightly longer. If you are able to make them yourself I suppose that would offset some of that additional cost.

  4. #4
    Lt Commander
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    Just be sure to use the proper and quality hose when you change everything out.Please don't try to use radiator hose.It sinks boats.

  5. #5
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    I am not aware of any recommendations for or against stainless from the ABYC.
    ~ on the hook ~

  6. #6
    Lt Commander
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    Quote Originally Posted by TimG View Post
    I am not aware of any recommendations for or against stainless from the ABYC.
    I forgot to comment on that.Since I will be building my boat from scratch,I've searched out info on stern drive installations.I do not recall anything specific on this subject.

  7. #7
    Lieutenant JG
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    The way i understand it is that you do not want to use stainless in any high heat situations. The reason being is it expands and contracts a lot and will fail. This is why you don't see internal engine parts made from it, i.e. Cranks and pistons and what not. I have stainless rods and cams in my motor and they do fine, but the top end of a motor doesn't get as hot as the exhaust does. Use caution as stainless is very expensive. They used iron for a good reason! Good luck and good boating.

  8. #8
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    Matt brings up a good point, I believe the water is injected in at the elbow, depends on the exhaust system though. On mine the temps of the elbows aren't too bad and you can place your hand on them. Get an infrared thermometer and you can check the temps, however they will still contract/expand.
    ~ on the hook ~

  9. #9
    Lt Commander
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    Thanksguys for the response the elbow that im referring to is not the riser where the water is injected. Into the exhaust its in the piping behind the engine so that the exhaust will exit the boat. It has 4 inch wet exhaust hose on both ends.

  10. #10
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    So you are talking about the portion that goes through the helm? If so temperature should not be a factor.
    ~ on the hook ~

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