502 MPI Exhaust
 

What is a resonable HP gain expectation changing from stock exhaust manifolds to some form of performance exhaust without making any other changes. Is it worth the money based on selling the stock manifolds which are fresh water.

Thanks
Jon

10-20 HP or about a 1 mph gain. Stock exhaust has little to no value unless someone local needs it. Its not worth shipping costs.

Keep what you have unless you are having issues with your stock exhaust.....not worth spending the money

https://cimg1.ibsrv.net/gimg/www.off...ac74721e9.jpeg
I wouldn’t expect anything for performance gain. However, the stock 502 does revert slightly even in stock form, plus the stock mercruiser manifold/risers suck. Just a poor design and will leak eventually.

Mine are full length stainless marine so I never have to worry about reversion. Plus it sounds a little better too since it’s dry to the tips outside the boat. I saw zero performance gain over stock.