How much boost will a stock 2004 575 handle anyway

How does she Idle? Got any video

so is it safe to say you gained 4-5mph just by switching to the larger blower and running almost same boost??

With its low compression, I don't see why 7lbs, maybe even 8lbs with that 871 non intercooled, with better headgaskets. I bet the 871 is making less heat at 7lbs than the 256 was at 4.5 lbs.

You are correct.

What speeds were you at with stock 575's. the other 2 40's I use to run with were true 70 mph boats on GPS. Congrats on your build. I've heard great things with minor upgrades to 575's.

That's awesome. Pretty much what I gained going from 250 blowers to 420 blowers.

Im Not anti intercooler, but I don't know many guys running roots who installed chillers under their blowers and picked up 5mph or better. Especially in a boat like a 40 outlaw! Good stuff.

Now try cranking the boost up another 1-2psi, and report back. The 871 will do it no problem.

I agree. Makes me rethink my current mods.

Those giant satin finish blowers are just beggin tk be painted merc blue, I think they would look sick!

4bus...are what mods did you do to your 575's? Chillers, heads, cam?? Did you have them Dynod? Jus curious.

Eric

In the process right now. Following precision marine's set up (pmefi.com) Same 575 story-

full roller conversion
3.5 pulley
ECU reflash
120 degree stat
plumbing for chillers but going to test without to start.

My objective was to improve more than it was to add speed. I thought the boat performed well on top stock, and was very reliable.

My issues were idle, loading up, soot/extreme richness, and known HG failures. The cam change was a give in, seeing that we had the heads off.

I have to say if I did not read oso I most likely would have left them in and just did an ecu and pulley.....the talk on this site scared me into tearing the heads and cams out of engines with 60 hrs!

My engines and boat also sat for 8 years, showing only 3 hrs on the ecus. Builder saw signs of spring fatigue on a few valves and the edge of an intake lifter was missing tiny pieces and marked the cam. Lower end is perfect.

Man I ramble.......sorry, back to the OP :lolhit:

Do you think temp on an intercooled 250 is similar to a non intercooled 871 @ 7lbs? Thanks for the input

What speeds were you seeing when stock?

I cant really answer that. My guess is the non intercooled 871 will have a cooler temp than the intercooled 250, and much longer blower life.

I have never seen a test on a typical "superchiller'' style intercooler, providing temperature data or efficiency numbers. I know if I was manufacturing a product and selling it, I would provide those numbers, especially if they were worth talking about.

I am also not aware, of anyone adding a superchiller, keeping the same boost level, and netting mph gains anywhere near what the OP did, or myself, from stepping up to a larger blower. Sure, adding a chiller AND upping the boost, has netted speed gains, but then again, it should. Boost is HP.

I am running 6-7 lbs on my new DMPE rebuilt blowers without chillers. Running aftermarket aluminum heads though. Eddie @ Young Performance got me some nice custom ground roller cams. This combo is perfect.

And fast....

Runs a consistent 88 mph in the summer heat. Cooler days it has broke 90. Last run of last year with water and air temps in the 50's it did 92.7 on the limiters. I wish it ran like that every day. The thought is chiller would give these engines cold weather performance year round???

I am hoping to see a real 5 mph gain from my mods with out a prop change or chiller, then go from there.

I am running the plumbing for the chillers but waiting on the install. I want to get spring run numbers, then summer heat numbers first. I will then add the chillers in the heat of the summer and see there is a a change. I will also monitor the knock sensor activity with and without chillers.

This is my plan, we will see if I have the same desire this summer.

Your plans , if you follow through , would produce some great information for guys like me .

when its 90 degreese and 90 %humidity,the chiller will help increase hp more than on a cool,dry day.

Do it!!!!:evilb:

I agree!!!!

I am at 9.5psi intercooled.

With cam change and limiter raised, I would think that 5mph is very doable without a prop change.

you are an animal