Is it Worthwhile to Change from 3" to 4" Exhaust Collectors in a Crusader 454?

[drseth]

Hi,

I had a mechanic come over yesterday to check the tired engines, and , yes, they need long blocks. He said that 3" exhaust collectors cause too much back pressure and robs 10% of HP. Is this BS or is he telling the truth?

He gave me a price of around $5000 for pulling the old engines out, swapping accessories, and putting the long blocks in, along with complete rebuilds of the Velvet drives. Is that a good price for that?

Also, should I have the shafts checked out or any other service performed, while the boat is out of the water, besides pressure washing, bottom painting, and changing the zincs? I would like to get all of my ducks in a row so I can use the boat relatively trouble-free.

Finally, I have read from some engine builders that they have a 420 HP long block that will use less fuel than the stock long block. Is this BS or is there some truth to it? I know about valve overlap and water intrusion, but I am not sure about this.

Dr. Seth Anderson
1979 Pacemaker 33 Sportfish Crusader 454's
1991 Albemarle Express 24 ft
1991 Aquasport Osprey 200 20 ft. Suzuki DT140
1988 Henry O Challenger 15 ft Suzuki DT55
1966 Hunter Skiff 14 ft. honda BF5A
2002 Tremblay 12 ft, Evinrude 9.9

 

[makomark]

On the exhaust, we've found that the more open the exhaust, the easier the engine breathes and the more efficiently it will run. The big factor in determining the mod's "worth" is how you run the engines. In our case, we were running 4-6 hours a day, at cruise (offshore fishing). The economy improvement was slight but noticed. Big difference was the "out of the hole acceleration" - a huge improvement.

On the price - that is a local issue. Best to check around and see what the going rate is. I'd say it isn't out of line. Another factor is how easy it is to access the engines.

Checking the shafts for trueness is never a bad idea, especially when things are "apart" and you have no first hand knowledge. Its a no-brainer if it can be done locally. May want to consider new cutlass bearings if you're gonna pull the shafts.

I've seen some of those same "more economical" claims for the higher rated engines. On the surface, I'd label it BS without seeing the details. You can make a factory engine much more efficient but it takes lots of $$$. A 33 footer is about the upper end for gasoline engines so I wouldn't expect any huge improvement. Now, if somebody's willing to give you a written guarantee and they have a track record, it may be worth further consideration.

FWIW, we went from the log style, rear outlet, 3" tubes (into a 4" outlet Y) to center riser (now the current standard) manifolds with 4" S/S elbows, which flowed into a Y with a 5" outlet thru the transom.