thirdchildhood

iTrader: (6)

Silent Choice can be used with a stout cam at idle and very low speeds only. You will need the proper Y pipes that mix the water a little further downstream. The 525 has a fairly radical cam. I don't have all of the specs but duration is 244* exh & 236* int. The Mercury 525 service manual says that silent choice can only be used up to 2,500 RPM. I only use mine at idle like when idling around a yacht club or trying to talk to someone.

seth0687

So best course of action: delete silent choice and get aftermarket manifolds and long risers?

Thanks guys.

mike tkach

iTrader: (3)

in a nutshell,yes,and i can tell you what i have done as far as max dration cam with eddie marine manifolds,but bob madera is the expert and can tell you exactly what combination to go with,and he can set up with the parts at a fair price.

BBCLiberator

iTrader: (2)

Post some pictures up of your current manifolds, I'm thinking they may already be at least the 496 parts which are fairly decent, I'm sure one of the guys here could identify them the color has me confused...

seth0687

Here are some pictures of the motor, I know it's not pretty, the previous owner didn't take care of things....Everything is going to be gone through and restored/cleaned/fixed/done correctly when I get the motor out.













Thanks again for all the help,

Seth

Budman II

iTrader: (1)

Those look like Gil manifolds and risers on the boat now. You should be fine with any cam that is not larger than about 224* / 236* @ .050 and 112* LSA - I ran a flat tappet cam with these specs on a 454 with stock manifolds / risers and Silent Choice for years with no reversion issues. A cam with 114* LSA would probably give you a little extra insurance.

Now if your goal is truly 575 - 600 HP, you are going to have to go with a full header and lose the SC. You will probably want to look into a good set of heads like the AFR's and a much stouter cam to achieve this. Bob M. would be they guy to talk to about cam choice for a goal like this.

thirdchildhood

iTrader: (6)

My cam is "larger" than that and Mercury says that Silent Choice is good up to 2,500 RPM. One other thing I like is that I get a lot of waves breaking against the back of my boat when sitting still and the Y pipes give me some peace of mind that if any water should get by the internal flappers it will run down the Y pipe and not over the hump and into the engine.

Budman II

iTrader: (1)

I guess that would be the case so long as the flappers in your Y-pipe are functional, but a big swell against the stern could also try to force water up the Y-pipe. I always like to park with my diverters closed to the "thru-prop" position to give an extra measure of protection from water coming up the tail pipes.

Also, I ran my boat with the exhaust thru the prop all the way up to around 3500 RPM without any issues, but if you have more overlap than the cam I ran, you might have issues.

seth0687

im going to go pretty big on the cam so bob from marine kinetics said i will need new manifolds and long risers dry to the tip of the riser.

thirdchildhood

iTrader: (6)

I have seen my internal flappers stay open a few times. A wave should close them but if it doesn't then the water should run down the Y pipe. I like the idea of closing the divertors when the engine is off. That would block the tips completely off. A few years ago there was a noise complaint on my local lake and the water fuzz asked me to plane out to see how loud my engine was. I took a chance and did it through prop. He still said it was too loud but didn't have a decibel meter. He was clueless that the exhaust was not coming out the open tips!

When I repowered I spent several thousand bucks getting my exhaust set up proper so that I could keep the Q&Q. Like I said before though, I only use it at idle when I know the loud exhaust would not be appreciated. TTBOMK the 525 EFI uses just about the biggest marine cam there is since it is N/A. I could be wrong though. Q&Q is very nice if you can keep it even if only for idle speeds. I can pull up to another boat and flip the switch and be able to talk with the engine running. I can also idle through yacht clubs and check out the rides without pissing everyone off and getting kicked out. I use it if heading out early and it's all fishers at the ramp.