Need Engine Help Quick!!
 

Ok everyone, I need some help here. As many of you know, I have been redoing my engines over the winter. What I did was take my stock 525SC’s and replaced the blowers, carbs, pulleys, belts, etc. Prior to this I was running 88-90 with standard Bravo’s on my single step 35’ Fountain. After the new 420 mega-blowers, new carbs, belts, pulleys and nose cones on the drives were added, I’ve lost 3-5 mph. Obviously we thought it was the drives or props so we tried a 26, 28 (original), 30, and 32 pitch prop with little to no difference in any of them. We then tried 2” shorter drives because we could not get the props to blow-out getting on plane like they had been, still no change and still lower speeds. We got anywhere from 5400-6000rpm’s with then props, but nothing helped. Finally, we thought maybe the engines had a compression issue or leak, but we tested them both and they were perfect. The only thing we can think of is that we aren’t getting the horsepower we should. If so, how’s that possible? What could possibly be mismatched that would be causing this problem? Should I spend the money to have them dynoed, then find out it isn't producing the horsepower, but not know where the problem is or find out they are producing more with lower speeds? Everyone working on this is completely frustrated!! Help!!!!!!!

Is your boost pressure higher now than before?

still running 5lbs of boost

When you replaced blowers, carbs etc, you gave yourself the potential to run more boost while creating less heat. Now if you want more horsepower, you'll have to turn up the boost. Continuing to tune will probably get back the lost mph, but to go faster you will have to change pulleys.

Did you have the carbs bench flowed and tuned to you setup? When I had mine done at Pro Systems they found 62 more ponys, best 400.00 I ever spent worth every penny!

Shouldn't the bigger blowers alone produce more horsepower at the same boost?

Yes, the carbs were completely rebuilt and flow smooth.......

Perhaps, if the charge is cooler and denser. But the larger blower also takes more hp to turn. You have lost a sizable amount of horsepower so I would look at what has been changed. I'm assuming that all normal tune up stuff has been done like making sure it's firing on all cyl. and sparkplug wires and cap and rotor are good. The first thing I would look at is carb jetting. Is the engine getting enough fuel? The second thing is ignition timing. Did you retard the timing any? I don't think the nosecone slowed you down any.

The boat also had scoops installed, so the engines are running really cool. All the top end engine stuff has been gone over a few times and checks out. Brand new spark plugs, wires, etc. We had problems with the carb lines, but they reworked them to flow smooth. The timing was set and doesn't seem to be a problem. We are just totally lost...............

What carbs are you using?