Exhaust manifold replacement

[Smasher]

G'day raiders

My mechanic told me that the exhaust manifold on my Mercruiser 3.0 stern drive should be replaced every 5-7 years. Looking through the service history, I can see that it was last replaced in 2013 (previous owner).

He quoted me $2200 to do the job. As did another marine I called. 

Now I've seen the kits for sale around $680. eg: 

http://www.ebay.com.au/itm/3L-3LX-MERCRUISER-MANIFOLD-KIT-GENUINE-4CYL-3-0L-12-MONTH-FACTORY-WARRANTY-/231930871324?epid=1571059663&hash=item3600283e1c:g:yzcAAOxyoA1RPVDP

My questions are:

1. How do I know when it needs replacing?  I know that if it rusts through, salt water will pump through the engine and FK the whole thing so you definitely do not want to wait until that happens. But at the same time I don't want to do it prematurely if I can put it off for another year or two.

2. Does this seem steep or reasonable?  

3. Is it something I can do myself or with a mate in a day with basic tools (socket set etc).

Cheers

 

Edited July 5, 2017 by Smasher

[rickmarlin62]

hard to pick when to do it..its fairly easy to do as we have replaced them on two milligan nippers with 3.0ltr mercs  and had no dramas...rick

[Smasher]

Thanks rick. Roughly how many hours does it take?  (just trying to calculate hourly rates of a mechanic)

[rickmarlin62]

only a couple  dependant on how many beers are consumed during process...rick