Has anyone out there tried the Hardin Marine Stage I, Stage II or Stage III upgrade kits for the 525 EFI or having the computer re-programmed by Whipple? I'm just curious as to what any of these do for the low end and mid-range. I have a 30' Eliminator Cat with twin 525's and am Ok with the top end of 110, but low end and mid-range is terrible. My next step would be the Whipple SC Kits, but I was hoping to find out how well these other kits work.

I don't know from experience but ive heard Raylar makes a nice 600hp 525 upgrade. Might be worth a look.

Call Eddie Young, at Young Performance Marine.

Thanks Mild.

Triple, if you have a minute, read the 525 thread in the General section. There are a few things that you should do before doing Whipple's ecm upgrade. By the way, Whipple's upgrade is awesome. You will see the biggest gains in the mid-range. You will have to run 91 octane fuel. If that's not available, we have done some for 89 octane, by not adding quite as much timing in the mid-range. The 525's have a very "lazy" timing curve. The timing really doesn't ramp up until 5000-5200. The tune adds up to 8* of timing in the mid. In addition, it adds a little more timing up top, along with a bump in the rev limiter.

Let me know if I can help in any way. We have done quite a few of them, so we have been able to find the problem areas.
Eddie

I'm also curious if anyone has done any of the Hardin kits....

I have the stage 3 kit on my 525's. Picked up about 5 mph (70-75 full load any day top speed)