Exhaust System Crusader 57 MPI 330 hp

"I am installing a new 5.7 MPI

"I am installing a new 5.7 MPI in my 26 foot Tollycraft. I currently have dual 3" exhausts with the original 270 Crusader, with about a 4' run from the manifold to the stern. The new engine comes with 4" exhaust ports. Does anyone have a recommendation about upgrading the system to a 4" or will I be ok if I stay with the 3"?"

"Since the gaseous exhaust col

"Since the gaseous exhaust collapses to moisture during the run, most exhaust systems are already way over-sized.

Super high performance car exhaust system are 3 inch, and they have hot gases flowing through them. Marine exhausts reduce the volumn dramatically when the water enters. I'd stick with the 3 inch.

FInally, there's adapters out there to reduce it down from 4 inch.


Jeff"

"Greg,

If it is a simple ma

"Greg,

If it is a simple matter of changing the thru-transom fittings, to 4" I would do that. If there is a muffler involved, that's a different matter. While the 3" exhaust is sufficient, most engine manufacturers went with the 4" to allow more flow of both exhaust and water through the elbows. The cooling ports in the 4" elbow will tolerate much more build-up of scale and corrosion and therefore last longer. If you have a muffler and do not wish to incur the cost of replacing it, I would consider installing fittings to reduce the hose size from 4" to 3" just prior to the muffler. I'm sure Barr or Osco make such a thing.

I would not install any reducers if it is straight exhaust.

Good Luck
Rick

P.S. Do yourself a favor upgrade or install a good boat mounted fuel filter prior to the engine, I recommend RACOR. That 5.7 has a pre-filter on the fuel pump inlet which is not easy to get to in many installations. Your old carb was very forgiving compared to the system on this MPI and the filters are much finer. Any scale flaking from the inside of your tank that would have easily passed through that old carb will become trapped and easily clog the new pre-filter. It's best to catch it before it gets that far."

I was told by Crusader reps no

I was told by Crusader reps not to add a fuel filter other than the one supplied with the engine because it might affect fuel flow (pressure) after the fuel pump.

Is this true?

"Brian, It is true if you cho

"Brian, It is true if you choose one of those cheesy $2.59 in-line filters from Pep Boys. Any restriction in fuel flow should be avoided, but a 1% restriction from an additional good quality marine filter is much better than a 90% restriction caused by a clogged filter you can't get to to change (like the pre-filter Crusader is now using). Good luck, Rick"