Hmm. As much as I repect Teague I question an additional 50 hp by changing the fuel pump to an Aeromotive, that is a bold claim! The 575 never had a fuel delivery problem stock, in fact it has always had too much fuel :D Maybe the claim comes from turning the regulator down from stock vs programming the BPW in the ECU (the proper way).

Where is the 678- 700 claim coming from? I would assume the 3.25, 3 inch pulley, and adding fuel volume with the aero stuff to feed that boost?

3.5 = 650
3.25 = 678
3 = 700

What pulley do you have?

The 575sci is 550 at the prop, 575 at the crank....stock.

I don't have a prop shaft dyno, most don't......so most aftermarket mods are referred to as crank shaft power so the world can relate, without doing the merc math.

The way you learn is to put out bad advice? You started up my shorts, questioning my set up, recommending plugs 4 full heat ranges hotter to the OP, and making out-landish claims and comparing my boat to yours (there is no comparison, we have different bottoms)

Why should I be at 104 mph? I could be at 110 mph if I wanted. I want a boat that works every day, and is rare to break. Sure there is speed to be found with short lowers, 5-6 blade props, bottom work, things to lower my slip and put even more stress to my XR drives that are already being fed too much HP.

I'll take my 98 mph every day, and 101 mph on the 5850 limiters when the conditions are right. 15 percent slip is not the best, but drives are in the water, and 15 takes a little bit of the stress away.

There is one thing I agree, you are making HP if you are running he speed you claim, and turning the RPMs you claim with a side by side small step lightning. Where your HP came from will remain a mystery I guess? Because an MSD box, with 3.5 pulley and chiller won't get you turning 5800 rpm at 100 mph in a 38.

What props are you spinning to 5800 ?

I agree, after the first 60 hrs on my engines from new, the builder described what he saw as "dangerous piston wash" I was getting AFRs under boost stock tune that would dip into the 9s! This was after the cam change, and increased boost!

SB !!!!!!! you are a Gentleman and a scolar!~! I thank you so much. The stock plug heat range too cold I am pretty sure See pic. And maybe I have some of the problem Rob described going on? This motor uses less fuel than my other one i beleive though

Cooerlman, Jason and his dad have a lot time with blowers and coolers plus sell a cooler.- of course they are at Lotto doing the shootout and the rest of us are stuck up here. I know for a fact they have done a lot of tuning on the dyno plus have a lot info from their testing. Maybe he will chime in after his vacation. Had to bust on Jason, he is a cool dude, no pun intended coolerman.

I'll give them a little plug again no pun intended.

www.pfintercoolers.com

I picked up a solid 8MPH...hit 81 a few times but 77-78 even this time of year. I'm actually getting ready to take her out and some data logging with MEFI Burn.

Do yourself a favor and start by zeroing out the bpw vs ect cold start (choke). It is not needed and give terrible readings until the engine reaches 140 degrees. I don't know who at merc thought the engine needed to be at 8 afr until it was warmed up. I fiddled for a while then just took it out, even on the coldest of spring days I still have readings on the rich side at start up, but now I can actually move the sticks from dead cold and rev them up clean.

Good luck with your tune. I tuned mine to 11-11.4 full boost. 12.5 cruise, and 12.5-13 idle. Some say go leaner, but I am happy with that set up. Clean but on the safe side.

If you are seeing a big difference in readings from one engine to the next take a close look at map senson, and ect sensor (different than the gauge on dash) also you can peak at the injector spray patter with the spark arrestor off. Use timing light triggered off cyl 1 and point it at the spray for a clear reading.

Here's a thought. Start by leaving temps out of the equation.

Boost is a result of backpressure from pistons, valves, etc.
5PSI is 5PSI is 5PSI
Doesn't matter if it's a 256, 14:71, turbo or hair dryer.
A 575 w/256 @ 4PSI @ 5K RPM makes X HP and a 575 w/8:71 @ 4PSI @ 5K RPM makes the same X HP
A 256 makes more heat so you may loose power. On the other hand, spinning more mass(8:71) takes more power. It's probably a wash at these boost and RPM levels.

I would think that the 256 would create better low end power but run out at the top, or at least become less efficient because of heat, not to mention the bearing issues. Whereas the 8:71 would have a harder time building boost at lower RPM's because of leakage but could keep up with the demand of higher RPMS, all the while creating less heat, but demanding more HP to turn.

Now, we're at say 4500RPM and goose it to 5K. I'd think the 8:71 would be more responsive to that demand(by milliseconds) than the 256 but ultimately they would end up at the same HP at 5K RPM.

If you could keep the air temp down and bearings alive, put a 1" pulley on front of the 256 and it'd keep up with the 8:71

Then we go to Whipples. I think they can create the same boost as any Roots style blower without the low RPM pressure loss, hence more bottom end, and take less HP to turn because of their smaller mass.

Enter the world of turbo's. Same deal as small Roots to larger roots without the parasitic HP loss, just backpressure issues to deal with.

Don't mind me, just thinking out loud, rambling....and bored.

Have a great weekend, I'm gonna go clean my plugs.
Rob

Use timing light triggered off cyl 1 and point it at the spray for a clear reading.[/QUOTE]

Cool idea!

Stock 575 sci motors with yR5's for Years and no burn on the pistons plugs or anything,. How is this possible. That is the question. Maybe the blower shop makes just that much better 250 blowers. I am at about 6-7 psi boost. I would really love to know .