Merc. 525 upgrade
 

I just found out I have a bad valve on my stock 525 in my Kryptonite. Also found a bad header caused the problem. What options are out there to upgrade the top half of the motor to make more reliable power. Maybe 625 HP. Not looking for a whipple or anything crazy.

You're not alone - we found cracked headers on the 2010 700SCI's in my 36. They caused minor damage to one of the ports - we had to weld up the head. We're replacing the headers with the CMI Gen X headers, they supposedly have a much better lifespan.

without going up in cubes, after market heads and upgraded cam, ecm retune I dont think you'll get to 625 + hp..........that TB and intake are very restrictive with air flow just like the 500 EFI intake

I had an Active Thunder 37 with 525s and they had the Stage 1 Whipple tune. The original owner posted his speeds with various props when he owned it (engines were stock). It was hard to compare as he was in salt water and I was in fresh. Either way, the best I ever saw was 83 mph. I looked long and hard for a good method of increasing my power to the 600 range.

Your engines as they are are producing around 545 to 550 hp. The whipple tune is good for 20 hp, but I saw no speed gain over other ATs with he same engines. The only thing left is to port the TB, flame arrestor, and the throat of the manifold. That is good for around 15 hp. All of that is going to cost you a lot of money and you might if you are lucky see a 3 mph gain.

I would suggest leave the engine as it is. If you want a real performance increase buy a Whipple for your 525. That will put you around 780 hp, you will notice that, and in the end, it isn't going to cost much more than all the other band-aid mods that don't do much.

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That’s interesting.