the dyno sheet on my 500'sconverted to 540's read 685hp , but the boat does not run like a 685hp boat . I have another cig that I run with that has a set of zull 675's in it and he runs 10-12 mph faster everyday than I do . same side by side engines , same drives ,both twin step! only 2 differences is his boat has ITS boxes and his has 1.36 gears and I have 1.50 no box . he runs a 30p 4 blade and I ran a 30 and cant turn the rpm.

The intake program is he machines inside the intake and opens up the throttle bodys to flow .

Noise? My hogans have the billet runners but even if not don't really agree with that train of thought. Been running mine for 2 years no timing issues yet. The only reason I can see for not running them is cost. They are spendy.

Glad to know somebody using them , cost was not a "major " factor in my decision .

I couldn't wrap my head around the 'noise from sheetmetal intakes causing timing issues' as I was thinking actual timing settings. Then boom, my brain light went on, lol, I ran into this with exhaust noise from the pipes themselves on a particular engine. Not marine so don't worry.. The metal 'pinging' for a lack of a better word was detected by the knock sensor, and thus timing pulled out by the ECU.

So...this is my guess with the sheetmetal intake since the air flowing in all intakes is quite strong and quiet violent as it goes in many different directions many times a second. Coupled with non cast or billet, I guess this could be possible depending on gauge thickness of metal, construction and reinforcemnt techniques, etc.

Do I win a prize or just lose another braincell ? LOL.

The knock sensors in the merc 525 platform are turned off.

I struggled with that one too, but now as you described, makes more sense. Thanks SB

If your tuning a mefi anyways the knock sensitivity could be turned down. Did this on a street motor i used a mefi 4 on with solid rollers that was picking up mechanical knock, smitty

the issue is you arent getting the rpm you need to take advantage of the rpm range, so yes, you would leave power on the table. your 540s able to breathe should be able to run to 57-5800 easily, by running them limited to 54 its like running a race in 3rd gear and not being able to use 4th.

C.I.M any results on the 525efi upper and lower intake modifications. Thanks!

Wow I missed some bad ass builds. Thanks for the links. Someone should archive these.