Exhaust Manifold Replacement

[300sflyer]

Howdy folks!

This is my first post here on the forum. Hope I can be of help to some folks and learn from others at the same time.

I have a 94 Mariah [I'm the third owner] with a Mercruiser 5.7 in it, and am wondering about the condition of the exhaust manifolds. The engine currently runs great [only fresh water] with no issues, however there is no hour meter on the boat, so I can only geuss at the number of hours of use. Based on the overall condition, I would say approx 500 hours.

I know that extensive damage can result with a rusted out exhaust manifold, and am wondering if I should just go ahead and replace them? Is there a certain # of hours or years of operation they are rated for? Are OEM ones the only real way to go, or are aftermarket ones [possibly aluminum?] just as good or better?

Thanks in advance for your comments!

 

[jerryjerry05]

Re: Exhaust Manifold Replacement

At 13 years the manifolds can last another 10 years or maybe 1year. Fresh water doesn't hurt them as much as salt.The riser can be removed and checked for blockage.
But the only way to be sure is replace them.
OEM is a lot more costly and they won't last any longer than aftermarket.
Barr or OSCO make a good unit.Aluminum,I'm not sure they make them.
Save your money and buy aftermarket.
Buy new mounting hardware and gaskets.Jerry

 

[Bondo]

Re: Exhaust Manifold Replacement

If its been a fresh water boat all its life, the manifolds should be fine.

Ayuh,....

Up here on the Sweetwater Seas,...
Freeze Breakage is about the Only reason for replacing exhaust manifolds....

I've got'em dating back to the 60s that still appear nearly New....

 

[chiefalen]

Re: Exhaust Manifold Replacement

First welcome aboard !

My 2 cents leave it alone, fresh water they can last forever.

But do keep a eye on the running temp.

If it ever goes near 180 then it's time to pull the risers.

Change out the impeller in the lower unit every 5 years and you will be fine.

T-stat same thing unless the temp starts to rise.

Good luck !