My granddad designed engines back in the twenties and knew a lot about them. He always said that engine improvements have to be made on the intake side, the exhaust takes care of itself.

I have heard that center dumps don't improve performance much, and may not be worth the effort. Perhaps someone on the forum has done this and can say what the change is, if any.

I installed center dumps on my 1980 single engine and had a problem. I got water backwashing into the engine because on a single the engine is mounted low right down into the V and the system was too low. The original centerdumps have two parts, the riser and the manifold. The replacements, which I used, have three. There is a 1" spacer between the riser and manifold. The spacers are stackable. The fix for me was to add another 1" height with another spacer and longer bolts. I think the parts were made by OSCO. The other thing I remember is that you have negotiate price for the whole order. Some places charged less for the riser than other places but more for the manifold. The last bit of advice is to only make the upgrade when you need new exhausts not for performance which is supposed to be about 15 HP.

You realize that you'll have to re due all the downstream exhaust piping? Pain in the butt! From what I've heard the only difference is seen on a dyno, at WOT and max rpms. In addition, logs make the motor easier to work on--less stuff in the way. Finally, some of the center riser parts are no longer made, so you'll have to do some scrounging.

I'd stay with the logs. Seriously.

Jeff

One can buy a lot of gas for what all that EFI claptrap costs!

Jeff

Thanks for all the comments!!!! I am convinced to just enjoy the boat as it is...

Hmm. The O2 sensors on my Mustang are well downstream of where the water would be dumped in if it was a boat. And I don't suppose the sensors would care for the salt. Good point.

Fuel injected aircraft show little efficiency improvement over carburated ones, but the "set up" is done by the pilot in-flight with the mix lever. Again, constant rpm. I didn't think of that, either.,

Most power gains come from better rpm due to better breathing. To take advantage, the props must be adjusted, not so fun.

I don't know why, but the changes seem to be coming to outboards. The Bombardier (Evinrude) 2-strokes being a good example. I guess marine inboards will always have to be an adaptation of what works on the highway rather than a new design for boats.

Actually, my boat is powered with engines that find their widest use in forklifts and generators.

I based my example on a 38' Chris Craft glass boat that had 430 Lincolns in it. It would cruise at about 16 miles per hour and get .5 to .6 mpg. We re powered it with big block mpi Chevy engines and now get 1.2 to 1.5 at a cruising speed of 28 mph. I would call that a significant increase it both speed and economy. Look into what a efi with pod drives will do for speed and economy. The connections used on a modern f i engine are what they call weather pack and do a very good job of sealing out the elements. For repairs you plug in a diagnostic computer and it will generally tell you what the problem is and from there it's pretty much screw driver and wrench time. In the 40 years that I have worked on cars and boats for a living I've seen it go from points, crappy carbs, real crappy wiring and connections, 6 volt batteries and generators to what we have now. I'll take now any time and hope to live long enough to see the next generation of marine and automotive engineering. Like it or not it's coming and it can't be stopped so we might as well embrace it and learn how to deal with it and learn how to repair it. Rick

Evinrude has raised the bar in out board technology to a very lofty position. The new 4 strokes are nice but there is a price to pay in weight.